Energy Recovery from Solid Waste

Abstract

The growing amount of solid waste (SW) and the related waste disposal problems urge the development of a more sustainable waste management practice. The organic wastes that are generated include food scraps, yard debris, paper, wood, and textile byproducts. According to most studies, almost all landfill gas is created by the breakdown of organic waste in combination with the naturally occurring bacteria in the soil that is used to cover the landfill. They are inevitably linked to the treatment and disposal of solid waste. In this instance, treatment is utilized to restore or recover important materials or energy, control waste generation, or manage trash disposal before it is deposited or discarded in landfills. A disposal site where solid trash, such as paper, glass, and metal, is buried between layers of dirt and other materials, such that land around the site is less contaminated. Waste-to-Energy (WtE) technologies are being developed globally. The essential concepts of available technologies and several specific technologies’ processes are summarized. Technologically sophisticated processes (e.g., plasma gasification) gain increased attention, with an emphasis on energy and material recovery potential. This chapter ends with a comparison of the various technologies, highlighting variables impacting their application and operational suitability. More budgetary allocation for technical support by the government is also recommended in this chapter. This will help to promote solid waste management by reducing, reusing, and recycling waste. It will also help to retain employees by providing a good wage, benefits, and training. As a result, WtE technologies have the potential to make a significant contribution to the growth of renewable energy while also reducing landfilling expenses and the associated environmental implications. However, deciding between the two options necessitates further financial, technological, and environmental examination using a life cycle assessment (LCA) methodology.

5.1 Energy Recovery: Introduction

Waste management is essential for urban infrastructure since it protects the environment as well as human health. This is a significant political dilemma as well as a technological, environmental issue. Waste management is inextricably linked to a variety of problems, including urban patterns, resource use rates, employment and income levels, and other socioeconomic and cultural determinants. Preventing and eliminating waste benefits the environment, public health, and protection, as well as the economy. Adhering to the “less is enough” philosophy protects human health and safety by minimizing exposure, thus reducing the need for environmental disposal. As a result, recycling costs are lowered because there is less waste.

The industrial revolution ushered in the age of automation, in which machines operated autonomously of human labor. Then there is the fact that energy demand has increased dramatically, and men are increasingly seeking energy capabilities. Power is inversely proportional to the Human Development Index (HDI). The energy consumption per capita is a proxy for HDI. Most energy sources have been extracted for a long time from fossil fuels such as coal, oil, and other sources. These fossil fuels, however, have substantial reserve limits. Furthermore, these fuels emit greenhouse gases (GHGs) and cause other important global environmental impacts, collectively known as global warming. At the same time, as human society has grown, energy demand has increased exponentially. Humans began moving energy from one type to another as technology advanced.

Solid waste management is the efficient organization of activities involved in the collection, separation, storage, transportation, transfer, processing, treatment, and disposal of solid waste. Solid waste management objectives are to control, collect, use, handle, and dispose of solid waste in the most cost-effective manner possible while adhering to applicable national laws and regulations. Waste is produced in and from various sectors; residential, commercial, manufacturing, and other waste generated from these sources is highly heterogeneous and exhibits a range of physical characteristics. The heterogeneity of waste produced is a significant impediment to its use as a raw material.

Climate change happens naturally and has done so many times in the Earth’s history. However, over the last two centuries, climate change has arisen because of industrialization and human behavior. Currently, the atmosphere is exceptionally conducive for human life, but with the increased pace of climate change, we could be moving toward a less hospitable environment for humans. It is agreed that this can occur naturally over time and that we can adapt. However, as the abuse of fossil fuels and natural resources accelerates the pace of climate change, we will be unable to respond quickly enough or with sufficient resources.

The recent stages of waste generation must be reduced, and material and energy recovery must be increased, as these are considered necessary measures toward an environmentally sustainable waste management system. Primarily, incinerators were used to diminish waste mass all over the world, but incinerators are now being used to recycle energy. The extracted biogas from the landfill is used to generate electricity and heat. Material recycling and food waste composting are the most relevant systems from the standpoint of the public [1].

The issues caused by solid waste can be tackled by using cutting-edge technologies. There are numerous waste-to-energy (WtE) technologies available today that efficiently recover and use energy, including anaerobic digestion (i.e., solid-state anaerobic digestion), thermal conversions such as pyrolysis/gasification and thermochemical conversion (i.e., bioreactor landfill). Every piece of equipment is specifically designed for the composition and volume of solid waste [2]. Without verifying the magnitude and structure of waste produced, it appears challenging to suggest appropriate waste management plans and technologies [3]. The composition of solid waste is critical when constructing a solid waste management system. Recycling, composting, landfilling, and all other waste-to-energy technology solutions can be included in this management scheme. The components of the waste stream influence the type of energy recovery equipment used. As a result, the technological and economic feasibility of a particular waste-to-energy scheme is determined by waste stream characteristics.

For the period 1970s and early 1980s, a lot of countries around the world were severely impacted by the excessive expenditure of trade in oil and the shortage of low-expenditure substitute oils. This situation triggered a quest for alternative energy sources, which rekindled interest in municipal waste as one potential source. There were two reasons why the enhanced fascination in the energy capability of urban waste was inexplicable: (a) a significant proportion of the waste could consist of fuel components, i.e., materials which could be used for heat generation; and (b) incineration of municipal waste, dependent on country, and exploitation of the waste heating generated in Europe.

Numerous combustible elements of municipal solid waste are also recyclable, and therefore able to use as a substrate for biological transformation to a fuel gas that can be distorted directly to the energy (i.e., direct conversion to heat energy) or able to stockpile or transferred for subsequent conversion (i.e., implicit conversion). The energy potential for urban waste is different both in terms of energy content and ease of “extraction.” Many different methods exist for extracting energy from solid waste. Figure 5.1 illustrates a graphical diagram of the various energy recovery processes, as well as the different forms of fuel and energy sources that can be extracted from municipal wastes. As exemplified in the diagram, energy recovery can be undertaken by or deprived of automated, manual, or mechanical/manual waste handling preceding to conversion (i.e., pre-processing). Without pre-processing, energy recovery is achieved mainly by transforming waste into the form in which it was generated. Pre-processing is used to recover energy using one or more of the methods depicted in the diagram. The primary purpose of waste pre-handling for energy recovery is to isolate the organic from non-inflammable and inflammable fractions from the remainder of the waste.

Fig. 5.1

Techniques of recovering energy from solid wastes [4]

There were no sanitary control schemes in place prior to 1800. Garbage was burned or dumped in alleys, streets, and rivers [5]. As the 1800s approached, several families dug disposal pits as a substitute. Animals, both wild and domestic, were used for waste disposal in the 1800s. Cholera and yellow fever epidemics prompted local governments to improve sewage treatment and water sources by the end of the 1800s. Instead of developing an integrated waste management system after WWI, contractors for waste management were outsourced. Multiple transfer stations were built to serve small household units after a common disposal site was found. During the 1930s and 1940s, the federal government imposed location limits, preferring dumpsites to be built away from waterways.

Both traditional solid waste management efforts and new solid waste management efforts aim to avoid disease transmission. Due to the individual household emphasis, traditional efforts were simplistic and disjointed. Furthermore, no consideration was given to the effects on the climate. They were created based on a lack of understanding of the connection between waste and disease. The new initiatives, on the other hand, are incorporated and planned with the general interests of public health and environmental protection in mind. The current efforts begin with the generation of waste and end with its disposal [5]. The existing efforts necessitate a continuous monitoring system as well as a spill prevention system. Traditional approaches focused solely on the protection of surface waterways.

According to the United Nations Environmental Program in 2012, there is a large potential for energy recovery from solid waste based on continuously developing urban waste management systems and a rise in waste-to-energy investors to the tune of $1 billion [6]. Furthermore, compared to other sources of energy, waste-derived energy is simple to generate and inexpensive and would be a welcome alternative during these difficult economic times.

The composition of the wastes determines the fuel benefit of refuse-derived fuel, as well as the actual incineration of the material. The comparatively high moisture content of putrefiable materials, for example, must be diminished before ignition can occur. The energy required to remove the wastes must either come from the energy released when dry raw material is burned, or it must be supplied by combusting supplementary (e.g., fossil) fuels alongside the wastes. Agreeing to the statistics in Table 5.1, the municipal wastes produced in numerous developing countries can be putrefiable to the tune of 50–70% on a wet weight basis. The volumes of discarded paper and plastics, on the other hand, are comparatively small.

Table 5.1 Difference of solid waste description worldwide (% wet wt) [4]

The low amount of flammable material means that the relative fraction of dry, combustible materials is minimal. Not only that, in certain developed countries, but the percentage of total urban garbage also made up of ash is quite significant (e.g., up to 60% where wood ash, coal ash, or both are major waste byproducts of domestic activities). Together, these features of waste will result in the creation of a system that uses energy, rather than one that provides it. It may not be reasonable for underdeveloped nations or may be only feasible in a limited number of locations or conditions.

5.2 Energy Recovery Context

“Waste-to-energy” or “energy-from-waste” (often abbreviated to WtE) is a blanket term that covers a wide range of thermal treatment techniques and technologies. It’s a technique for recovering energy (in the form of heat) from waste combustion and turning it into electricity. This energy is either returned to the National Grid or local heat and power networks, or it is used to deliver both electricity and heat (combined heat and power (CHP)) to nearby communities or industries.

Alternatively, waste might be the residue left after recyclables have been removed from a general waste stream, or it can be a refuse-derived fuel (RDF) or solid recovered fuel (SRF) generated at a Mechanical Biological Treatment (MBT) plant. Biodegradable and non-biodegradable materials are used to make RDF, which has a lower and less predictable calorific value than SRF. RDF is made from these materials. SRF is designed for industrial processes such as cement kilns and power plant furnaces and is made to a specific standard such as that issued by the European Committee for Standardization.

For example, in the United Kingdom, energy from waste has endured from a scarcity of public trust and acceptance due to early low-quality waste incinerators, which were mostly disposal-only plants that burned waste to minimize its volume. The adoption of modern WtE treatment has also been sluggish, owing to the 1970s’ preponderance of landfills. Today, a significant driver is the Waste Framework Directive’s statutory-backed waste hierarchy. This places a premium on waste management with the aim of preventing, reusing, and recycling it; therefore, obtaining energy from waste should be reserved for genuinely remaining waste unable to achieve by these approaches.

Incineration, waste-derived fuel combustion, and more advanced technologies like pyrolysis and gasification are examples of available methods (producing fuel gas from the waste by heating either a zero or low-oxygen environment). Thermal treatment alone does not account for all the environmental advantages; energy conversion equipment utilized in conjunction with it does. Furthermore, the process’ overall efficiency will be influenced by the amount of energy required to run it.

In 2013, the UK’s first commercial-scale gasification plant started operations, with the capacity to generate 6 MW of electricity. By 2020, waste-derived renewable electricity from thermal combustion in England is projected to increase from 1.2 TWh to between 3.1 and 3.6 TWh, depending on how much of the solid recovered fuel generated in the UK is used. Table 5.2 summarizes the common technologies and associated efficiencies for WtE systems.

Table 5.2 Regular instruments and proficiencies for WtE systems [7]

Waste management is a vital aspect of the urban system because it guarantees environmental and human health security. It is a highly political concern as well as a technical, environmental issue. Waste management is inextricably linked to several issues, including urban lifestyles, resource use patterns, jobs and income levels, and other socioeconomic and cultural considerations. Waste hindrance and minimization have beneficial effects on the climate, human health and safety, and the economy. By minimizing exposures and reducing the demand for disposal on the environment, the “less is better” principle offers good quality safeguard of human health and safety. The cost of disposal is also reduced as the amount of waste generated decreases.

Increased living levels and high rates of resource use have had an unintended and detrimental impact on the urban environment, resulting in the production of wastes well beyond the ability of local governments and agencies to manage. Cities are currently dealing with issues such as high waste levels, associated costs, waste management processes and methodologies, and waste effects on the local and global climate.

However, these concerns have initiated a window of opportunity for cities to pursue alternatives involving the government and the private sector, new technology and disposal practices, as well as behavioral improvements and public awareness. Many cities around the world have successfully addressed these problems, as shown by good practices.

There is a need for a full rethinking of the concept of “waste”—to determine if waste is waste. A rethinking that entails the following:

• 1. WASTE to become PROSPERITY

• 2. REFUSE to become RESOURCE

• 3. TRASH to become CASH

There is a strong need to move away from the existing waste disposal strategy, which focuses on communities and uses high energy/high technology resources, and toward waste handling and waste reusing (which includes public-private partnerships, aims for ultimate waste minimization—driven at the community level, and uses low energy/low technology resources). Increased community involvement, recognizing economic benefits/waste recovery, focusing on life cycles (rather than end-of-pipe solutions), decentralized waste administration, mitigating environmental impacts, and integration outlay costs with long-term goals would all be defining criteria for future waste minimization initiatives.

The repurposing of “waste” products is referred to as resource recovery. It entails gathering, sorting, and processing materials that are historically regarded as waste and converting them into raw materials for the creation of new items. Recycling and composting are two of the most well-known methods for resource recovery.

The process of reclaiming materials that were previously believed to be unusable is known as resource recovery. It is not waste management, which is the industry norm for most garbage companies. Traditional waste collection and transportation firms collect and transport waste to large-scale, single-use facilities such as landfills or incinerators. Unlike waste management, resource recovery acknowledges that such resources also have value. Via our innovative projects, services, and technology, ecology makes it easier to extract the remaining value of these resources. The waste hierarchy of waste reclamation is depicted in Fig. 5.2.

Fig. 5.2

Waste hierarchy

The aim of resource recovery is to maximize the usefulness of all resources while landfilling only those that are no longer useful. Over time, we anticipate that the volume of landfill-bound waste will decrease to a marginal level because of our resource recovery efforts. Recovery of resources is important for environmental sustainability. Food scraps, yard trimmings, recycled paper, plastic, and fabrics are recovered for reuse, thus avoiding the use of new materials. These are only a few examples of recycled products that support global agriculture and manufacturing.

Because the Waste-to-Energy process is irreversible, the decision to reuse urban wastes for the primary goal of energy recovery has an impact on ecological resource utilization. On the one side, recovering the waste’s calorific value and reaping the associated benefits could be preferable to losing the waste’s energy recovery capacity to landfill disposal. Irreversible energy usage, on the other hand, can overlook more sustainable resource uses of that material, such as reuse, recycling, or reclaiming for substantial intrinsic recovery and higher exemplified energy value.

Energy processing, also known as energy recovery, is a broad term that refers to a variety of technologies and processes that convert the material being treated into a fuel that can be used to generate electricity, steam, or heat. The term “energy recovery” has traditionally been correlated with waste management technologies, and it refers to a variety of processes, including landfill gas generation, biogas generation from organic waste, thermolysis, and feedstock recycling for fuel production and incineration. The core principles of this technology are widely considered to be the most widely used technique for waste-to-energy conversion. Furthermore, incineration units are usually the most widely used waste management system and the most effective treatment for plastics. The vital governing parameters of incineration units are defined in detail, as well as feedstock characteristics and incineration applicability. It illustrates the different types of incineration units used in waste management that can be used to handle municipal and plastic solid waste.

5.2.1 Recycling and Energy from Waste

Energy technologists have been focusing on environmentally friendly processes that can turn waste materials into usable energy because of the quest for renewable and alternative energy sources. Waste-to-Energy (WtE) technologies take advantage of urban waste’s abundance to produce electrical and heat energy, which is accomplished through a variety of complicated conversion methods. Municipal waste, unlike fossil fuels, is considered a renewable energy source because it is made up of many biological materials that are part of regular life in a municipality [8]. The accretion of organic waste can be due to population shifts toward urban areas. As a result, WtE facilities in the country are in desperate need of growth.

The first waste-to-energy (WtE) incinerator was installed in Nottingham, United Kingdom, in the late nineteenth century. The procedure entailed the burning of organic materials with the recovery of energy as a result. Pyrolysis/gasification, refuse-derived fuel (RDF), plasma arc gasification, incineration, trans-esterification, and anaerobic digestion are the six major WtE technologies currently in use around the world. WTE technology selection is inspired by a variety of considerations, involving quality, waste type, geographic location, and labor ability requirements [9].

The provision and enhancement of required infrastructure and services continue to outpace the growth of urban areas. As a result, waste management issues have arisen, as most municipal governments face significant financial constraints, limiting their ability to provide efficient waste disposal. Owing to a lack of comprehensive waste management strategies, all towns, cities, and development points face the problem of littering, waste dumping, and inappropriate waste disposal. Many people in the world today are realizing that what some have discarded as waste has meaning. Communities in many developing countries, for example, make a living by aggregating waste plastics, wastepaper, and cardboard boxes, to name a few.

Even though the world produces 4 billion tonnes of all types of waste every year, only a quarter of that waste is recycled or reused. Although there are valuable items like cardboard, plastics, glass, and metals in municipal solid waste (up to 50% in developing countries), most waste is sent to landfills. Given the low prices of recycling products on the global market, recycling and waste claims have been barely profitable. Recycling is the process of converting a commodity or resource that has attained the end of its valuable life into usable raw material for the creation of a new product. Waste recycling is defined as the method of reclaiming material that would otherwise be discarded as waste. It is a technique for recovering resources.

As a result, the new waste management trend is to view waste as a resource to be utilized rather than a nuisance to be treated and disposed of. The material could be removed and recycled, or it could be turned into something else. Secondary resource recovery, recycling, and other terminology are used to describe the method of removing resources or value from waste. Waste disposal is being increasingly recognized as unsustainable in the long run due to the finite availability of most raw materials. Waste reuse is a type of recycling that refers to reusing anything that would otherwise be discarded without any transformation processes. Wastepaper is an excellent example of reused waste. Newspapers, magazines, and books, as well as cardboard and mixed sheets, are examples of wastepaper.

Thormak [10] described recycling potential as the environmental impact of a material’s output, with recycled material serving as a replacement for less environmental impact from recycling processes and associated transportation. The recycling potential can thus be briefly described as the amount of embodied energy and natural resources that can be saved by reuse and recycling. According to a study by, waste policies must be viewed in the context of the wider life cycle, which includes resource use and development, as well as waste reduction and recycling. Prevention and recycling of other thin materials, as well as energy recovery and pretreatment, are both options for diverting waste from landfills. The management problem has become an increasing issue for national governments, local governments, environmentalists, academics, and the public.

The value of recycling wastes has been recognized in surveys conducted by the United States government and other non-government organizations in the region. The standards for safe waste recycling, on the other hand, have not been standardized. According to studies, the USA recycles between 7% and 15% of its waste. If recycling is done correctly, it can eliminate waste or garbage issues. Many NGOs (Non-Governmental Organizations) and private sector companies have taken the initiative to segregate and recycle waste at the community level.

Classification findings are a method of determining the criterion structure of a waste stream for a specific area, which is then followed by sampling and sorting procedures. These studies are beneficial for creating assessments about waste management policies and ensuring accountability to taxpayers. Classification implies the approach of sorting a waste stream based on the handling proposed for the waste stream. Various processing systems are used or have the potential to be used in waste management activities, ranging from treatment and recycling to recovery and utilization; the applications used are determined by the needs and priorities of a specific prerogative. Table 5.3 outlines waste management collection systems and their purposes.

Table 5.3 Handling methods for urban solid waste [11]

To manage the sampling, sorting, and analysis of their MSW sources, numerous provinces use a description by the ASTM International standard D5231-92 [12]. The sampling procedure, which defines the minimum sample size and number of samples to collect to achieve a representative sample of the population, is more widely used. Individual jurisdictions are free to change and customize the list to meet the needs of their premeditated sample, with a minimum suggested number of sorting categories of 13 (Table 5.4).

Table 5.4 Suggested element groups for classifying MSW [12]

Several characterization studies are performed to thoroughly examine the content of the MSW flow and the source (demographic sampling analysis), which allows assumption as to the need of dealing with waste management plans. The organization of MSW classification methodologies is also driven by composition studies. Once an effective classification framework has been developed, characterization will help determine the viability of processing technologies based on waste composition. Non-putrescible organic matter, for example, may be used in gasification waste-to-energy processes; however, a greater substance of inert materials would decrease the process’s performance.

5.2.2 Waste-to-Energy Classification

Various waste produced enter land and water bodies without proper treatment, which leads to substantial water pollution. They also contribute to air pollution by emitting greenhouse gases such as methane and carbon dioxide. Any organic waste from urban and rural areas and plants is a resource because of its capability to degrade and produce electricity.

The obstacles initiated by solid and liquid wastes can be significantly diminished by employing environmentally friendly waste-to-energy technologies that enable waste to be treated and processed before disposal. These initiatives will lessen the volume of waste generated, create a significant amount of energy and substantially decrease environmental contamination. As the country’s energy deficit grows, the federal and state governments are becoming more interested in sustainable and renewable energy sources. One of these is waste-to-energy, which is gaining traction with both the federal and state governments.

Furthermore, as an extension of waste characterization, urban solid waste classification seeks to cogently sort out the material structure in a way that is useful for assessing the viability of future waste processing technologies. This classification focuses on waste-to-energy (WtE) prospects. Combustion, gasification, pyrolysis, and anaerobic digestion are the main waste-to-energy technologies.

All of these include the recovery and conversion of organic carbon from feedstock to a usable energy source. A review of published literature suggests a standard MSW classification system for WtE applications based on an understanding of the processes involved and the working conditions available. There are limited MSW categories for biofuel applications, but all seem to agree on four main classes based on the physicochemical properties of the materials and potential WtE applications for each part, as described in Table 5.5.

Table 5.5 Novel analysis on MSW categorization approaches [11]

Since waste-to-energy technologies are still in their infancy, with an emphasis on advanced biofuels, little emphasis has been placed on thermochemical activity classification. It would be useful to develop an adequate category to aid in classifying whether further handling and fractionation of the MSW stream would benefit these applications.

5.2.3 Waste-to-Energy Is a Sustainable Waste Management Option

The waste hierarchy seeks to foster long-term sustainability. In the sense of the waste hierarchy, energy from waste may be classified as either recovery or disposal. To be classified as rehabilitation, facilities must meet the criteria for the process’s energy efficiency. For example, the UK government asserts that energy-to-waste must, at the very least, not compete with, and should preferably promote, recycling, reuse, and prevention. Recovering electricity from waste is a realistic way of dealing with it.

Most WtE plants generate electricity. Operators are increasingly looking for ways to use the heat produced, a process known as combined heat and power (CHP). WtE has the potential to play a small but growing role in producing electricity and supplying heat to communities. It is also valuable as a domestic energy source that contributes to energy protection. Consider that expanding the use of residual waste’s energy value prior to final disposal will make a more rational and sustainable contribution to our energy policy. With the proper production, refuse-derived fuels could provide stable energy prices for industrial purposes. Waste-to-energy also has the benefit of being non-intermittent, which means it can be used in conjunction with other renewable energy sources such as wind or solar. The environment has a significant impact on the lives of all living beings on this planet. When it comes to waste and its disposal, waste incineration is one of the earliest and most successful methods. Essentially, it is a method in which household and industrial waste materials are burned. The waste materials are converted into ash, flue gas, and heat during this process. Incineration may take place on a small, medium, or large scale, depending on the type of waste materials.

Waste materials or organic compounds, including household, toxic, and medical wastes, are burned in the waste incineration process. Since incineration requires combustion, it is also known as thermal treatment. Nowadays, incinerations aid in the conservation of electricity by preventing it from being lost.

The planning framework should promote the productivity benefits of combined heat and power (CHP). This will necessitate a greater focus on strategic encouragement. Further deliberation is needed in the National Planning Policy Framework and the waste management strategy. Planning policies that provided guidance for how new ventures should use CHP technology at an appropriate scale would provide a major advantage.

While the use of low-carbon and renewable energy is currently promoted in new projects, and many waste-to-energy plants are designed to be “CHP ready,” the reality is that there are so many obstacles to the growth of heat networks without a strategic approach to energy use within our towns and cities. The cost of retrofitting infrastructure to congested utility corridors, as well as the challenge of obtaining reliable offtake of heat at a guaranteed price are among the obstacles that must be overcome for the financial model to function in practice. A clear policy structure in the planning system will help to promote this progress.

As a result, for the sake of humanity’s future, all human processes must be made sustainable. This should include all technical processes as well. One of the most critical technical processes for which technological solutions must be built is energy generation. Except for nuclear and tidal energy, most of the energy generated by humans is derived directly or indirectly from solar radiation (more than 90%). Fossil fuel, which is fossilized solar radiation energy captured by plants, accounts for most of the energy produced today (80%). Due to limited supplies and environmental load from greenhouse gas emissions, mostly CO₂, fossil fuels cannot be considered renewable or sustainable. Furthermore, the reliability of fossil fuel supply is in doubt. Renewable and renewable energy sources, primarily focused on solar radiation (photovoltaic, wind, and so on), are currently receiving a lot of attention. Biomass is one of these outlets. Because of its short carbon cycle, it does not always impact the concentration of CO₂ in the atmosphere. Biomass, if used in a sustainable manner, has the potential to contribute 20–30% of humanity’s energy production.

Currently, biomass accounts for 13% of total energy provision, although this includes almost all conventional cooking and heating in developing countries. For a significant proportion of the human population (more than 40%), biomass is the sole source of energy. It is estimated that a significant portion of agricultural and forestry waste (equivalent to 50% of global crude oil production) can be converted into energy while avoiding undesirable food and feed/energy competition. Longer-term, the production of high-efficiency energy crops can be considered. To some degree, biomass can be (co)fired in modern equipment alongside fossil fuels without much pretreatment, as in the production of electricity in coal-fired power plants (green electricity). However, much of the current R&D effort is dedicated to transforming biomass into improved energy carriers that are equal to, or better than, the current fossil-based fuels.

Energy from waste has the potential to substitute a portion of conventional fossil fuels with biodegradable waste, thus reducing greenhouse gas emissions associated with electricity generation. In terms of carbon footprint, energy from waste is usually a more environmentally friendly method of waste disposal than landfilling residual waste. This, however, is based on the plant’s productivity as well as the amount and type of biogenic material present in the waste (high biogenic content makes energy from waste inherently better and landfill inherently worse). The debate continues about whether biomass combustion emissions (biogenic or short-cycle fuel) should be considered carbon neutral.

5.2.4 International Characterization Process of Energy-to-Waste Technologies

Tolerance for zero waste means empowering people to produce without or as minimal waste as possible. It means that nonrenewable resources must be conserved in the manufacture and distribution of goods and services, and waste and emissions must be avoided or held to a minimum. Waste management encourages sustainability in practices such as resource recovery, recycling/reuse, and composting by reducing raw material demand during processing as well as disposable waste, thus conserving nonrenewable resources. Individuals who care about the environment are more likely to employ pro-environmental behaviors such as recycling, composting, and source reduction. According to research, the public’s environmental attitudes in developed countries have been growing and widening to include a wide range of demographic groups other than urban, well-educated, and wealthy groups [14]. Recycling schemes, for example, have increased in the United Kingdom, Canada, and Great Britain, making recycling more accessible to more people and, as a result, lessening the impact of environmental issues.

Although little effort has been made in other countries to identify MSW, other attempts to describe waste have been made. This is because a greater emphasis is being placed on waste management protocols that address landfill alternatives as land space becomes scarce and in areas with a significantly higher population density. For completing urban solid waste composition studies, the ASTM International standards organization has established a methodology. Many jurisdictions use it to some degree because it allows for the customization of sample size and sorting categories to meet the needs of the study community [12].

A material flow approach is used in many state-wide studies in the United States to measure waste composition. This is finalized by comparing the total quantity of material waste in the waste stream with output data for the products that join the waste stream [11]. Many studies are also concerned about the impact of seasonality on waste streams and how this can influence the composition of the MSW. Greater humidity content due to higher organic matter during the roomier season can lessen conversion efficiency. The amount of waste does not seem to be affected by the season.

Around the world, most methodologies to characterization studies depend on demographic relationships to collect and compare fractions of the urban waste source. This outlook is useful for waste management approaches, but it is not useful for characterization for waste-to-energy applications. Although not all methods necessitate additional waste stream sorting, the proficiency of the practice can be enhanced if this is achieved. Magnets and sieves may be used to separate inert materials from the waste stream, such as metals, glass, and soils. In thermochemical conversion technologies such as gasification, inert materials cannot contribute to the energy potential and instead reduce the sample’s total energy density. The sorted MSW is often shredded to provide a more consistent feedstock called waste-derived fuel (RDF-3). This RDF is the material sent to energy-efficient waste plants [11].

A solitary ASTM International standard detailing the terms of the RDF classified them according to the process stage that was performed before it was used as a final feedstock (Table 5.6); due to restricted use by industrial applications, the standard was withdrawn; an equivalent standard exists for coal. These classifications may help to compare the processing levels needed for various WtE systems.

Table 5.6 RDF categorization [11]

5.2.5 Waste-to-Energy Projects

Waste production continues to grow, and landfills consume a significant amount of land, leaving cities surrounded by garbage and solid waste. In recent years, MSW incineration has increased steadily. Incineration methods can minimize the volume and mass of MSW by up to 90% and 80%, respectively, and incineration with energy recovery is one of the waste-to-energy (WtE) technologies [15].

According to Adapa et al. [16] the rising of energy demand has caused a stalemate among established energy sources, regardless of whether they are thermal, nuclear, hydro, or solar. It stresses the need for an alternative, highly feasible, and long-term energy source. According to the paper, municipal solid waste (MSW) has long been a safe and effective choice for waste-to-energy conversion. The paper also discusses the various conversion processes, such as incineration, pyrolysis, gasification, and biodegradation. The above technologies are compared using various physical and chemical parameters, with the aim of ensuring the environmental sustainability of waste-to-energy (WtE) systems. Their research concludes, based on assessment results, that biological approaches are best adapted for waste-to-energy conversion with the least environmental impact.

Methods such as pyrolysis, incineration, and gasification are quite efficient and productive but are also very dangerous because they emit dangerous gaseous emissions, which, without a doubt, contribute to global warming and the greenhouse effect. Fruergaard and Astrup [17] presented a study on the most efficient waste-to-energy conversion in life cycle assessments (LCA). The article states that two forms of urban solid waste can be used to produce electricity. Mixed high-calorific waste, one type of municipal solid waste, is better for the production of solid retrieved fuels, abbreviated as SRF, whereas organic waste is separated by the other. It is explained that co-combustion is equivalent to mass-burn incineration for solid recovered fuels. In their study, incineration was modelled for the case of mass-burn incineration. Both scenarios with and without energy recovery were included in the model. The biogas generated by anaerobic digestion can be used for a diversity of targets, involving transportation fuel, heat generation, and power generation, according to the report. There are various related findings for resource and energy use in life cycle assessments, such as emissions to air, soil, and water, downstream processes, upstream processes, and so on.

There are two distinct energy systems that must be considered when making energy substitutions. One is the current Danish scheme, which is based on fossil fuels. The other energy system is the possible failure system, which is entirely reliant on renewable energy. The article demonstrates that mass-burn incineration of solid recycled fuels combined with energy recovery save money in a variety of ways. Co-combustion, on the other hand, is much superior to global warming. If we use all of the heat from the incineration, there are two solid recovered fuel alternatives that are tested and compared to each other. In certain types of impacts, incineration with energy recovery is safer and superior to anaerobic digestion for organic waste.

The study by Peterson et al. [18] looks at the Baltimore Clean Air Act and suggests that the city needs a new waste management system. The passage of the Baltimore Clean Air Act, as well as the impending closure of the Wheelbarrow garbage incineration facility, indicate that current waste management programs in Baltimore must be plowed, according to the report. The paper discusses three key policy concepts that are inspired by other cities’ “Zero Waste” policies. Policies can promote residential and business waste management, as well as investment in an improved waste disposal system and waste incineration subsidy schemes.

The Wheelabrator Baltimore plant, as a green waste disposal alternative, provides a modest energy return at the same level as traditional waste disposal while emitting greenhouse gases and harmful pollutants. Closing the incinerators creates a slew of new problems, and the only way to deal with the inevitable increase in waste capacity is to take proactive measures. To make this possible, waste management policy choices and plans have been proposed. The first piece of advice is to use financial incentives to encourage businesses and residents to minimize waste. Most of the waste usually ends up in landfills, which can be eliminated by reducing waste sent to garbage incineration. In the short term, the priority should be on industries that generate the most waste, while in the long run, the emphasis should be on built-up recycling and zero waste initiatives. The second suggestion is to concentrate on recycling and composting, as well as to extend existing waste sorting facilities by constructing new compost facilities. The third proposal is to exclude biomass and waste incineration from the Tier 1 renewables band, as well as the tax incentives that go along with it [18]. According to the article, the method has both advantages and disadvantages. Although quick-response services are necessary when there are large amounts of waste in a landfill, focusing on residents would generate more awareness and investment. Additionally, outreach services can be extended.

However, when the first guideline is introduced, community and company engagement should also be present, and the one who participates will be given the Green Business designation. The benefit of the second approach, which is to move toward biogas plants, is that it would help to eliminate harmful elements in the environment while still producing compost. Many people will lose their jobs because of the closure of WtE facilities, further investments will be required, and the pace at which an existing landfill reaches capacity will increase. According to them, removing waste and biomass incineration from the third strategy will improve people’s health chances because it emits more carbon dioxide than coal. But, without them, it will be difficult to meet renewable requirements, which may lead to an upsurge in the price of energy.

A study by Bruner and Rechberger [19] has emphasized the value of incineration from the perspective of urban metabolism, demonstrates that incineration is critical for long-term waste management, and provides a technical overview of municipal solid waste incineration over time. It has been shown that human actions often result in waste. Without question, as waste management becomes more complicated and material turnover increases, achieving the objectives of “defense of men and climate” and “resource conservation” becomes more difficult. Waste incineration, which was first implemented for volume reduction and sanitary reasons, has undergone extensive growth. Waste to energy plants, when combined with waste reduction and recycling measures, play a major role in achieving waste management targets. Environmentally friendly emissions are ensured by sophisticated Air Pollution Control (APC) systems. Finally, it was discovered that incinerates are both essential and special for the complete destruction of hazardous organic materials.

Anwar et al. [20] discuss how greenhouse gases can be converted into fuels and useful goods. Global warming and climate change are mostly caused by carbon dioxide emissions. Global warming and climate change are posing a significant threat to the environment, human life, and ecosystem. Carbon dioxide emissions have reached dangerous levels, resulting in disasters such as droughts, tornadoes, hurricanes, flooding, and wildfires all over the world. Both tragic incidents have resulted in thousands of deaths and have had a negative impact on the economic growth of many countries. The use of fossil fuels also increases local air pollution, such as winter smog. Water shortage problems are becoming more prevalent as the world’s population grows. Carbon dioxide levels must be reduced to avoid any of these catastrophic events. All these issues can be addressed by extracting CO₂, storing it, and using it to make biofuel and other useful chemical products. This can be used as a substitute for traditional fuels. As a result, the economic and environmental conditions will be improved, and many jobs will be created. Additionally, this can be used to desalinate seawater to provide clean water.

The reduction of fossil fuel consumption and the conservation of resources have become gradually more crucial in current years. Greater recycling rates for usable materials (e.g., materials) and recovery of energy from waste streams could therefore be a key role in replacing virgin material production and preserving fossil reserves. This is particularly important in the case of residual waste, which is normally incinerated in the United States. Several energy consumption scenarios for two outputs were evaluated. The use of liquid fraction for biogas production and co-combustion in existing power plants were found to be the most environmentally friendly (especially in terms of global warming) and energy-efficient option. The waste refinery’s energy and environmental efficiency is primarily influenced by opportunities to reduce energy and enzyme consumption.

The amount of waste generated is directly proportional to the rise in gross domestic product, the rate of population growth, and lifestyle changes. Solid waste can be used to generate and utilize energy, particularly in megacities. The produced waste, which has the capacity to generate electricity, is scattered across the ecosystem due to a lack of management. It can be used to recover energy in the form of biogas, electricity, and fertilizers, among other things. These beneficial components are currently released into the environment because of open burning and dumping or into groundwater because of bad landfill conditions. Most of the budget of most cities is set aside for solid waste programs. However, only about half of the solid waste produced is collected, with the remainder being improperly disposed of at landfills, along roadsides, or burned openly without regard for air and water pollution control.

The exploration of various types of waste management technologies is hampered by a lack of knowledge, financial and institutional capacities, and in this regard, only a small number of treatment plants, i.e., composting plants, are operational in Pakistan. Consequently, it is important to analyze the socioeconomic and environmental implications of various types of waste-to-energy technologies that are currently in use around the world and to identify the adequate treatment facility suitably based on the criteria listed.

5.2.6 Waste-to-Energy Scenario

The world’s energy supply is currently dominated by fossil fuels. However, since fossil fuel reserves are small, generating energy from them is not a viable choice. Furthermore, as they burn to generate electricity, they emit greenhouse gases (GHG). Even with best practices, coal-fired thermal power plants emit 532 g of CO₂ per unit of electricity generated [21]. Global warming is a serious consequence of these emissions. However, over the last 10 years, global primary energy consumption has increased by nearly 2%/year. Figure 5.3 depicts the global share of various sources of primary energy consumption [22].

Fig. 5.3

Stake of various energy resources in core energy expenditure in the world [22]

Oil is thought to be the forerunner, preceded by gas. However, these resources’ reserves are finite, and their combustion emits significant GHG. These two factors have compelled scientists and policymakers to look for alternative energy sources. At various summits, world leaders introduced various strategies to reduce GHG emissions and protect the atmosphere. Table 5.7 depicts some of the most significant summits. These gatherings serve as a catalyst for the advancement of energy harvesting technologies from renewable energy sources. The key goal of summits was to reduce carbon emissions. Each nation was given a goal of limiting carbon emissions to a certain amount to minimize environmental pollution effects such as global warming.

Table 5.7 Various protocols for limiting carbon emission targets [4]

5.2.7 Advantages and Disadvantages of Renewable Energy

Renewable energy has the following advantages [4]:

• 1. It is generally clean energy.

• 2. The operation and the maintenance cost are low.

• 3. It increases regional/national energy independence as, unlike fossil fuel, these reserves are not confined within a particular boundary.

• 4. Accelerates rural electrification in the developing countries.

Despite all these advantages, renewable energy has the following disadvantages:

• 1. It is intermittent in nature, i.e., the electricity can be generated when the resource is available but not when it is actually required.

• 2. This gives rise to the necessity of suitable energy storage systems. The conventional practice is to store electricity in a battery. These batteries affect the environment and economy. There are also capacity limitations.

• 3. The initial capital investment is high.

It should be remembered that renewable energy has many benefits as well as drawbacks. Renewable energy has several drawbacks that are not only technological but also socioeconomic. As a result, appropriate need-based conversion technologies must be developed for the improvement of renewable energy systems. Renewable energy technology has not yet evolved to the point that it can be used to construct large-scale power plants. Furthermore, storage is a significant problem due to sporadic availability. The most convenient method of electricity storage now is electrochemical storage, which involves storing electricity in a battery and then releasing it when required. However, there are power, environmental, and economic constraints to electrochemical storage. The system’s cost is high due to the high cost of batteries. Batteries typically need to be replaced every 5 years, while most renewable energy systems last for 20 years or longer. Furthermore, the batteries’ disposal is not environmentally friendly. As a result, hybridization of various renewable energy systems is needed, which entails combining various renewable energy systems such as solar, biomass, wind, and others into a single system. As a result, distributed generation based on local resources may be a viable choice for energy systems. These systems are created to meet a variety of local utility demands while considering technical, socioeconomic, and environmental constraints.

5.2.8 The Nature of the Waste Considered for Renewable Energy

Waste management firms are experiencing a period of uncertainty because of the push to reduce landfill and dumpsite waste. When governments and businesses seek to extract value from waste, they must implement more sustainable strategies. Recycling and reuse will become more essential because of this. Strategies for waste-to-energy conversion are being built, and projects are being planned. Waste-to-energy converts solid waste that would otherwise be disposed of in landfills into energy by burning it and leaving a small amount of ash that can be reused as road or building aggregate, with the remainder (such as hazardous waste) being disposed of in a landfill.

The material produced by individual households and some small businesses is known as municipal solid waste (MSW). It reflects the historically discarded and disposed of post-consumer spent and surplus products. In the meantime, commercial and industrial waste (C&I), consisting of spent, unused, or unwanted materials occurring during the primary manufacturing, can be considered for use in WtE. As it is presumed that these will be channelled to some better treatment before being introduced as a prospective fuel, they will be used as process inputs into another operation. Biomass is an example of waste from industries that are abundant in Malaysia. Furthermore, construction and demolition (C&D) waste can be used as a waste resource in WtE. Building demolition or alterations, as well as spent or surplus materials provided by construction and engineering activities, are examples of this form of activity.

The products from these three waste streams are by their very nature combined or dissimilar. This is a direct result of the conditions surrounding their disposal, and it will have a significant impact on how the products are used in the future if they are not naturally discarded for landfill disposal. The ability to reuse or recycle materials is greatly improved when they can be presented in specified or homogeneous streams, as is the case with recycling of domestic cans and paper, source-separated garden waste, or source-separated wood, metals, glass, and plastics from C&I or C&D waste.

Even if the products in urban waste are uncertain, they all have certain wide-ranging characteristics. These wastes would generally contain:

• 1. Hydro organic element

• 2. : This material is derived from food waste, soiled paper, and organic garden products and originates mainly from lignocellulose biomass.

• 3. A biologically inactive or slow-burning high-calorific element: This substance includes plastics, textiles, footwear, and a small amount of wood, cardboard, and paper. It is primarily composed of hydrocarbons derived from crude oil, with some lignocellulosic material carried over.

• 4. Metals: This category of materials includes ferrous (iron and steel) and nonferrous (aluminum, copper, and lead). Metals may be extracted from the waste material in its original state.

• 5. A non-reactive element: This category contains ceramics, soil, grit, broken glass, and debris. These materials can be easily removed from the waste material that originally produced them.

As a result, the location or geography of a possible source of urban waste is a critical factor to consider when determining the feasibility of a suitable energy recovery route. Transportation issues associated with aggregation to create viable amounts, as well as the transmission of any generated electricity, are both characteristics that must be considered when verifying the definitive feasibility and sustainability of the WtE project. The following subtopics emphasize biomass and urban solid waste as potential energy resources.

5.2.8.1 Biomass Energy

Strong carbonaceous content extracted from plants and animals is referred to as biomass. These include crop and forestry residues, animal waste, and food plant waste. Biomass is organic matter extracted from terrestrial and marine plants and natural renewable energy sources over a limited period. It is a solar energy derivative because plants develop CO₂ from the atmosphere and transform it into hexose represented by the reaction:

$$ 6{\mathrm{C}\mathrm{O}}_2+{\mathrm{H}}_2\mathrm{O}\frac{\mathrm{sunlight}}{\mathrm{photosynthesis}}{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_2+6{\mathrm{O}}_2 $$

Biomass does not contribute to CO₂ emissions into the atmosphere because it absorbs the same amount of carbon that it releases when used as fuel. It is a superior fuel since biomass energy is carbon neutral. About 90% of rural households and nearly 15% of urban households use biomass fuel. Wheat, maize, and sugarcane are examples of agricultural products rich in starch and sugar that can be fermented to generate ethanol (C₂H₅OH). Ethanol (C₂H₅OH) can also be generated by distilling biomass containing cellulose, such as wood and bagasse. Both alcohols are suitable for vehicle fuel and can be combined with ethanol to produce biodiesel. The example of biomass energy from agriculture is shown in Fig. 5.4. The description of biomass energy resources is shown in Fig. 5.5.

Fig. 5.4

Potential renewable energy from agriculture biomass waste

Fig. 5.5

Potential biomass energy resources

Energy initiatives that use agricultural biomass to aid individuals or specific investor groups at the expense of others and the entire community face resistance. Policymakers, on the other hand, often neglect the social, economic, environmental, and spatial conflicts associated with agricultural biomass-derived energy. According to Geels et al. [23], multi-level renewable energy research is required, including considerations of different concerns, values, skills, and resources among citizens, growers, local and regional governments, and national governments, whose strategies should be explored.

Crop residues are a plentiful natural resource that is simple to obtain and store. Rice husk, wheat straw, corn cobs, cotton stick, sugarcane bagasse, groundnut, and coconut shells are examples of these materials. For use as a clean fuel, these are turned into briquettes or pallets. There are high-efficiency solid fuels known as “biofuels.” Sugar and rice, the world’s two main tropical food crops, are estimated to have a combined energy content of about 18 EJ, which is equal to the combined energy content of temperate crops. Fuels are now being used in large quantities:

• 1. Bagasse, the fibrous residue of sugar cane, is used as a fuel in sugar factories to generate steam and electricity for the factory. Facts: (a) Transporting bagasse might not be cost-effective; (b) Expanded waste recovery, combined with improved conversion performance, could result in up to 50 GW of generating power from sugar manufacturing around the world; (c) Another idea is to make ethanol out of bagasse.

• 2. Rice husks are the most ordinary agricultural residues in the world, accounting for one-fifth of the dry weight of un-milled rice. While having a high silica and ash content as compared to other biomass fuels, their consistent texture makes them ideal for gasification technologies. Several countries, like Indonesia, China, and Mali, have successfully operated rice husk gasifiers.

Forests, whether natural or planted, provide a plentiful supply of timber, fuelwood, charcoal, and raw materials for paper mills and other industries. Eucalyptus, Neem, Kikar, and Gulmohar are fast-growing trees that are cultivated along canals, railways, and on low-quality ground. In sawmills, wood, sawdust, and bark residue are produced. The forest also has a lot of foliage and logging debris. A significant characteristic of forest residue is its calorific value, which ranges from 4399 to 4977 kcal/kg for softwood foliage and 3888–5219 kcal/kg for hardwood plants. Here are a few things about forest biomass residue that you should know.:

• 1. Switchgrass, which can be found in prairies remnants, along roadsides, pastures and as wind breakers around farms.

• 2. Hardy, perennial grass can grow up to 1.8–2.2 m.

• 3. As a source of forage for animals, in wildlife habitats, or as a ground cover to prevent erosion.

• 4. Can generate up to 1000-gallon ethanol/acre.

• 5. An alternative that is currently not feasible needs 45% more fossil energy than the fuel generated.

• 6. More research is needed to improve the efficiency of the conversion process.

De Wit and Hoppe [24] report that agricultural policy and technological progress are key factors in exploiting the capacity of agricultural lands completely to generate energy crops. However, the absorption of energy crops and renewable energy derived from agricultural biomass is determined by a complex web of interconnected, multidimensional political, governmental, cultural, and economic processes, not only technological ones [25]. According to De Silva and Horlings [25], there is no systematic diagnosis and no holistic approach to resolving how and why low-carbon energy is not being used in rural areas.

The rapid growth of the population is increasing the market for energy and new technologies. Oil, natural gas, coal, and other fossil fuels are used in several science and technology applications, but the main drawback about these conventional fuels is that they are nonrenewable sources, implying that they cannot be used again after one use. As a result, renewable energy sources must be used in science and technology [26]. Bioethanol is one of the most useful energy sources that can be replenished by using crop residue. The aim of using biofuel is to substitute fossil fuels, which lead to emissions and the greenhouse effect. By processing sugar and ethanol for the markets, the production of ethanol from sugarcane benefits not only the climate but also the rural economy, which is Brazil’s main source of income. In addition, a byproduct of the ethanol process, bagasse, can be used to generate thermal and electrical energies. As large amounts of bioethanol are generated from sugarcane through fermentation, the residual product known as bagasse should be stored and utilized because it is extremely valuable in the production of thermal and electric energy [27].

Ethanol is the chemical compound ethyl alcohol which is a colorless flammable liquid. It is a renewable source of energy that can be used in place of petroleum products. Ethanol can be manufactured using an assortment of biomass materials that include sugar, starch, and cellulose. Three of the most well-known feedstocks are sugarcane (sugars), paddy rice (starchers), and grasses (cellulose).

Figure 5.6 shows the processes of bioethanol production from different resources. Notably, molasses is a byproduct of the sugar factory from which the remaining 40–47% sugar is unable to be processed conventionally. However, it can be fermented to produce alcohol using yeast (saccharomyces cerevisiae). Meanwhile, Fig. 5.7 depicts the global energy expectation statistic up to 2013.

Fig. 5.6

Bioethanol production

Fig. 5.7

Global energy consumption [28]

Grains high in carbohydrates are made up of starch crops. The structure of starch (C₆H₁₀O₅)n is complex, with several glucose molecules connected together in a long chain called disaccharide sugars. Prior to fermentation, the starch chain must be converted to sugar. Starch cannot be converted into fermentable sugars by yeast culture. Hydrolysis of starch with dilute H₂SO₄ or an enzymatic process may be used to convert it. Prior to starting ethanol processing, starch is converted into maltose and glucose. Meanwhile, cellulose found in wood, grasses, and crop residue contains a long chain of sugars, as well as lignin, which prevents sugar hydrolysis in plants. Polysaccharides are a complex substance that is more difficult to convert to simple sugars than starch. Cellulosic content is transformed by varying the acid concentration, operating temperature, and reaction time during special hydrolysis with dilute H₂SO₄ at elevated temperatures of 180–200 °C, which enables the product sugar to decompose into glucose and finally ethanol.

Brazil is the country that widely used ethanol derived from biomass in its Pro Alcohol program. Some facts related to the Pro Alcohol program in Brazil can be summarized as follows:

• 1. Over 90% of new automobiles run on ethanol derived from sugar residues.

• 2. The leading profitable biomass system in the world.

• 3. Founded in 1975, during a period of high oil prices and low sugar prices.

• 4. Stop fossil fuel imports for the first 25 years, saving $40 billion in direct interest savings on international debt.

• 5. At times, production approached 15 billion L/year.

• 6. Currently, most vehicles operate on gasoline with a 26% ethanol content.

• 7. According to 1999 estimates, the policy was reducing annual greenhouse gas emissions.

• 8. A reduction of nearly 13 tons of carbon dioxide emissions.

• 9. The economics of ethanol production are highly speculative.

• 10. Sustainability is critically dependent on global sugar and crude oil prices, which have fluctuated widely and often rapidly over the last 30 years.

5.2.8.2 Municipal Solid Waste (MSW)

There were no sanitary control schemes in place prior to 1800. Garbage was burned or dumped in alleys, streets, and rivers [5]. As the 1800s approached, several families dug disposal pits as a substitute. Both wild and domestic animals were used to dispose of waste in the 1800s. Cholera and yellow fever epidemics prompted local governments to improve sewage treatment and water sources by the end of the 1800s. Instead of developing an integrated waste management system after World War I (WWI), contractors for waste management were outsourced. Multiple transfer stations were built to serve small household units after a common disposal site was found. During the 1930s and 1940s, the federal government imposed location limits, preferring dumpsites to be built away from waterways. The first sanitary landfill in the United States was built in California, USA, in 1934, and the practice grew in popularity.

According to the United Nations Environmental Program in 2012, there is a huge possibility for energy recovery from solid waste based on continuously developing urban waste management systems and a rise in waste-to-energy investors to the tune of $1 billion USD [6]. Furthermore, compared to other sources of energy, waste-derived energy is simple to generate an inexpensive and would be a welcome alternative during these difficult economic times.

The development of municipal solid waste (MSW) as a thermochemical conversion feedstock for advanced biofuels is underway. Edmonton formed the first waste-to-biofuels partnership with Enerkem Alberta Biofuels; however, Canada has only recently begun to consider increasing landfill diversion rates through the incorporation of new technologies and programs, owing to a glut of available land and a lack of inducements to support make these new technologies as cost-efficient as landfill. A robust categorization system is needed to realistically discover the prospects for energy recovery from MSW.

Most developed countries, including the United States, Europe, China, Singapore, and Japan, produce energy from solid waste. Municipal solid waste (MSW) has been broadly used in recent years to create waste-to-energy (WtE) through conventional technologies such as direct combustion (e.g., incineration/combustion, pyrolysis, and gasification) or the processing of flammable gases such as methane, hydrogen, and other synthetic fuels (e.g., anaerobic digestion and refuse-derived fuel). Combined heat and electricity is the preferred option to increase energy productivity by using MSW. MSW that has been discarded can be used to generate electricity and reduce greenhouse gas emissions. Advanced MSW management technology with the added benefit of energy extraction from solid waste represents an encouraging choice for solving the country’s waste discarding problems [29].

MSW refers to combustible and non-combustible household, commercial, and industrial wastes that are typically disposed of in urban landfills. Because up to 80% of the carbon content of combustible MSW is extracted from biomass, it is widely referred to as a renewable fuel. MSW’s primary environmental concerns center on the potential negative impact of inefficient waste management practices on human health and the climate, including soil and water contamination, air quality, land use, and landscape. Current findings reveal that the new MSW disposal systems of landfilling and incineration (mass burn or combustion) are unsustainable due to their high greenhouse gas emissions [30].

MSW is currently disposed of in sanitary landfills, where it produces fuel gas, a valuable green energy source. Biogas is made from sewage that has been properly treated. Sewage is a liquid waste that is transported by water and is meant to be extracted from a community. It is more than 99% water and is exemplified by quantity or flow rate, physical condition, chemical and toxic components, and bacteriological condition. It is also known as domestic or municipal wastewater. Greywater (from drains, tubs, showers, dishwashers, and clothes washers), blackwater (the water used to flush toilets, along with the human waste it flushes away), soaps and detergents, and toilet paper make up most of the waste (less so in regions where bidets are widely used instead of paper). Surface runoff can be contained depending on the path it takes back to the ecosystem.

In several cities throughout North America, landfilling is still the primary method of disposing of MSW. While some cities are building sanitary or modified landfills to reduce leachate pollution, the issue of greenhouse gas emissions from landfills such as methane (CH₄) and hydrogen sulfide (H₂S) remains unsolved. Methane has a greenhouse gas impact that is 20 times greater than carbon dioxide [31]. Composting, anaerobic digestion, and ethanol fermentation are examples of biological process-based technologies with low reaction rates. The organic components of MSW are commonly used as compost or fuel for biological processes that produce a marketable product [32].

MSW is made up of discarded paper, plastic, food scraps, textiles, glass, metals, and other materials. Plastics, paper, lignocellulosic materials (wood, leaves, food scraps), textiles, and rubber are among the organic (carbon-based) waste stream components that can be converted into energy. Although not all technologies necessitate additional waste stream sorting, doing so will improve the efficiency of the process. Magnets and sieves may be used to separate inert materials from the waste stream, such as metals, glass, and soils. In thermochemical conversion technologies, including gasification, inert materials cannot add to the energy potential and just lower the sample’s total energy density. After being processed, MSW is often shredded to produce a more standardized feedstock known as refuse-derived fuel (RDF-3). This RDF is the raw material that is dispatched to waste-to-energy plants.

MSW is made up of both organic and inorganic fractions that come from various sources within a municipality [33]. Construction and demolition (C&D) waste and wastewater treatment sludge are usually excluded [7]. Most MSW streams are currently collected by municipalities and disposed of in sanitary landfills. Waste recovery plants are used in some areas to extract recyclable or compostable items from the waste stream. Other municipalities have turned to incineration facilities to minimize the amount of waste sent to landfills. As the land-dwelling zone available for landfilling has shrunk and environmental concerns have grown, there has been an increasing need to find alternative waste management solutions around the world. Due to limited spaces, these techniques have been established in leading European countries and other highly populated regions around the world.

To test thermochemical waste disposal technologies, jurisdictions must first analyze how they presently organize their waste streams to decide which technologies will be appropriate in the future. A framework for assessing a city’s energy potential from waste sources would be an invaluable tool for directing the transformation of Canada’s waste management platforms. The majority of current MSW classification schemes (Table 5.8) are focused on the material form or physical properties, according to Charley [11].

Table 5.8 Current procedures for classifying urban solid waste [11]

The most used classification scheme is based on material characterization, which is standardized by the US Environmental Protection Agency (USEPA). This method formulates the qualified elements of each material present in an MSW sample, which can be inferred to whole inhabitants. The list of materials may be adapted to satisfy the requirements of the prerogative that accomplishes the characterization. The findings of a characterization study can be used to assess the potential for physical, biological, and chemical production, as well as energy recovery and landfilling.

The organic, putrescible, or cellulosic properties of a material can help determine its composition in an MSW stream; these physicochemical properties imply whether energy can be extracted from a material, and if so, how much energy can be extracted. American Society of the International Association for Testing and Materials Standards [12] used this information to create a classification structure for energy recovery from MSW (Fig. 5.8), which incorporates various categorization methodologies to include a system for identifying appropriate energy-generating methods founded on the waste’s material structure. This outline can then be applied to the findings of a characterization analysis to verify the best energy recovery approach for a given jurisdiction. MSW is increasingly being investigated as a potential feedstock for biofuels applications globally, enabling the creation of more environmentally friendly energy solutions as well as a more efficient method of disposing of waste that was historically disposed of in landfills.

Fig. 5.8

MSW categorization scheme for energy recovery [7]

5.3 Energy from Waste Infrastructure

The rule of thumb of waste management is by following Lansink’s stepladder—setting the following priority for waste management: prevention > recycling > incineration with energy recovery > incineration > landfilling. Currently, waste management has strictly highlighted recycling and reinvigorating the waste and, if possible, waste prevention; zero waste. Annually human population keep increases thus, it proportionally reflects the accumulation of solid waste as clearly for the example, the total municipal solid waste (MSW) generation in the EU25 has increased from about 150 million tons in 1980 to more than 250 million tons in 2005 and is forecasted to reach 300 million tons by 2015 [34]. The big issue rise is where all these huge wastes need to be dumped? All the landfills are right now having a limited space; thus, serious concern needs to be highlighted here. Proper methods to deal with the entire categories of wastes are needed because without many people realize all these wastes can be converted into a value-added subject, energy. Thus, it will lead to a sustainable environment and achieve the united nation (UN) aims at 17 Sustainable Development Goals (SDGs).

5.3.1 Energy Recovery Concepts

Uncontrolled municipal solid waste (MSW) and waste disposal issues have raised awareness of sustainable waste management. Worldwide, waste-to-energy (WtE) systems are being developed to recover energy from garbage. Material recovery and recycling have become more important in MSW management. While there is a high level of awareness and concern for waste prevention and sustainability, the overall amount of MSW generated is expected to continue to grow over the next decade [34]. In developing a more sustainable waste management approach, WTE technologies are vital. This subchapter discusses waste conversion technology for the energy recovery. While certain WtE processes allow raw (i.e., as received) MSW as feed, the bulk of WtE practices preprocessed MSW to minimize changeable and/or inconsistent operational conditions, and also unpredictable product quality.

5.3.2 Waste-to-Bioproducts (WtB) and Waste-to-Energy (WtE)

The waste-to-bioproduct (WtB) commonly focuses on the recovery of the unseen potential energy in the municipal solid waste (MSW); thus, the typical term that is frequently highlighted is waste-to-energy (WtE) which is a recent concept waste management strategy. The primary goal is to dispose of garbage and transform it into resources that may be used to make a variety of products that will help to reduce greenhouse gas (GHG) emissions. Solid waste (SW) is a carbonaceous and nutrient-rich biomass that is frequently underappreciated in society.

Talking about energy, the exploration of the research on the production of alternative energy is getting catchy as it also reduces the reliability for us in depending on nonrenewable energy like usual fossil fuel. Energy from biomethane production has proven can be obtained by the pretreatment of MSW using hydro-mechanically process. It is recommended to have the hydrothermal (HT) process condition to optimize biocarbon recovery and HT process water (HTPW) biomethane generation in the AD process [35]. In order to further improve bioenergy production, the most advantageous alkaline HT method for maximization of biocarbon production as well as its AD favorable alkaline HT process water (AHTPW) for good biomethane generation have been identified and optimized. The optimal SW composition for anaerobic co-digestion with (a) mechanically treated SW, (b) HTPW, and (c) AHTPW were identified.

Agricultural residues, grass, energy crops, forest residues, and wood are examples of lignocellulosic biomass (LB) [36] (Fig. 5.9). Most of the LBs are comprised of hemicellulose (23–32%), cellulose (38–50%), and lignin (10–25%) [35]. Cellulose is a crystalline substance, whereas hemicellulose is a complex structure composed of different carbohydrate polymers (polysaccharides) [37]. Lignocellulosic waste such as corn residue and municipal food waste are the typical lignocellulosic waste which are commonly being consumed in the cycling process of the generation for bioproduct [36] (Figs. 5.10 and 5.11).

Fig. 5.9

Main waste categories: agricultural waste (straw seeds, cashew nutshells, corn seeds, olive kernels, miscanthus pellets); industrial waste (plastic, electric cable shredder, tires, densified plastic waste, etc.); timber industry waste (charcoal, bark, wood chips, bamboo, salix) [36]

Fig. 5.10

Corn residue and municipal food waste process cycle to generate bioproduct [36]

Fig. 5.11

Flowchart of typical conversion of corn residue industry [34]

5.3.3 Pretreatment for MSW

The abundance of LB in MSW need to be fully utilized, but the biggest challenges are to breakdown of the LB’s structure. Lignocellulosic biomass needs to undergo pretreatment to suit the requirement of enzymatic conversion; thus, it will lead to a high yield [38]. According on the design scenario of the national renewable energy laboratory (NREL), pretreatment is the largest contribution in the entire cellulose ethanol production expenses, in a study by Lynd [39]. The pretreatment methods are divided into (a) mechanical, physical, (b) chemical, and (c) biological. The simplest but the expensive approach is using physical pretreatments. The energy needed is huge due to the employment of the mechanical machine to decrease feedstock unit volume. Meanwhile, chemical pre-treatments use various chemicals, including acids, alkalis, organic solvents, oxidizing agents, supercritical fluids, and ligninase enzymes. Dilute acid pretreatment, ammonia fiber explosion (AFEX), and lime pretreatment are the best approaches, and they all produce significant and beneficial results. On the other hand, hydrothermal pretreatment is the process of pre-treating biomass with water. Using hydrothermal in pretreatment saves money because it eliminates the need for purchased acid for non-corrosive reactor materials and reduces feedstock size [40].

Pretreatment aims to diminish cellulose crystallinity, promote porosity, and destabilize lignin and hemicellulose (80%), hence able to maximize lignocellulosic pretreatment efficiency [41], pretreatment ought to not neglect these requirements:

• 1. enhance sugar formation or enzymatic hydrolysis sugar formation

• 2. avoid carbohydrate degradation

• 3. try to discard the formation of byproducts inhibitory as much as possible to the subsequent hydrolysis and fermentation processes

• 4. should be cost-friendly and cost-effective

Without pretreatment, hydrolysis yields are often less than 20% of theoretical yields, whereas pretreatment yields often surpass 90% of theoretical yields. Pretreatments are being created that are chemical, physical, biological, or combinations. The comparison of different treatments is shown in Table 5.9.

Table 5.9 Comparison of the pretreatment process [41]

5.3.3.1 Mechanical Comminution

Mechanical comminution is a collection of procedures that include chipping, grinding, milling, or sequence of these processes that are used to decrease the particle size of biomass. The size of the particles and the type of biomass have a significant impact on the amount of electricity required for milling.

5.3.3.2 Steam Explosion

This method seems like the most effective pretreatment where clearly because of the low use of chemicals and low energy consumption [42, 43]. The major constituent used to treat the feedstock material is high-pressure steam held at a specific temperature and pressure, followed by fast decompression. The biomass is heated with high-pressure steam for a few minutes and then decompressed explosively to change it physically and chemically. By this method, hemicellulose will be hydrolyzed, solubilization of lignin and the cellulose is made more accessible to cellulase enzymes [44].

5.3.3.3 Liquid Hot Water

Separation of biomass into its constituents is required for complete conversion to the highest value products. Whether steam or liquid water is utilized to fractionate biomass, the special features of hot, compressed liquid water must be exploited. This chemical bond breakage may be facilitated further by the elevated disproportionation of water at higher temperatures. Whereas hemicellulose is substantially deacetylated and depolymerized under such conditions [41], some evidence suggests that glycosidic bond cleavage does not require the presence of hemicellulose-derived organic acids. It is required to follow a mechanism other than acid hydrolysis.

5.3.4 Chemical Pretreatment

5.3.4.1 Dilute Acid Hydrolysis

The dilute acid hydrolysis method was extensively employed for the saccharification of lignocellulosic materials; yet, unswerving saccharification was associated with low yields due to sugar breakdown. Dilute sulfuric acid, dilute nitric acid, dilute hydrochloric acid, dilute phosphoric acid, and peracetic acid are the typical pretreatment approach used. Again, the cost-driven effect that has led the sulfuric acid pretreatment has become the greatest significantly studied because it is inexpensive and effective. Hardwood and softwood, herbaceous crops, agricultural residues, and wastepaper pretreated are among the feedstock materials which presented a promising yield once pretreated by the dilute acid.

5.3.4.2 Alkaline Pretreatment

Alkaline pretreatment techniques are focusing on the delignification processes, with a significant amount of hemicellulose solubilized in the water. The use of sodium hydroxide, or sodium hydroxide in combination with other chemicals such as peroxide, proved a convincing result for the degradation of the lignin after the pretreatments have been reported [41].

From the finding, this approach is best once the feedstock is coming from the agricultural residues and herbaceous crops than on wood materials [45]. Additionally, as Fan et al. [46] and McMillan [41] discovered, the efficiency of pretreatment is also dependent on the lignin content of the materials being treated. Alkaline hydrolysis is thought to occur via saponification of the covalent ester linkages that crosslink xylan hemicelluloses and other components [41].

5.3.5 Wet Oxidation

Wet oxidation is a process in which oxygen is used to oxidize substances liquified in water. Two major reactions take place during the processes: (a) a low-temperature hydrolysis reaction and (b) a high-temperature oxidation reaction. It is required to have particle size around 2 mm in length, while the water is added at a ratio of 1 L to 6 g biomass. By adding a chemical to the mixture (often sodium carbonate), the development of byproducts can be reduced significantly. The vessel is pumped with air to a 12-bar pressure. This pretreatment is done at 195 °C for 10–20 min. Wet oxidation can also be used to fractionate lignocellulosic material by eliminating lignin and solubilizing hemicellulose. Tremendously this method had shown a good degradation of a variety of biomass such as wheat straw, corn stover, sugarcane bagasse, cassava, peanuts, rye, canola, faba beans, and reed during the enzymatic hydrolysis where a high concentration of glucose and xylose were obtained.

The famous usage of wet oxidation is the method to pretreat the straw, reed, and other cereal crop residues which have a dense wax coating containing silica and protein. Wet oxidation benefits hardened biomass such as grape stalk (which contains tannins, a compound that hampers delignification) by up to 50% compared to pretreatment with sulfuric acid (25%) conversion.

5.3.5.1 Acid

Acid pretreatment involves the use of concentrated and diluted acids to break the rigid structure of the lignocellulosic material. The top usage of acid is dilute sulfuric acid (H₂SO₄), with the statistically shown that it is commercially used to pretreat a wide variety of biomass types such as switchgrass, corn stover, spruce (softwood), and poplar. Traditionally, diluted sulfuric acid is commonly used to manufacture furfural by hydrolyzing the hemicellulose to simple sugars (such as xylose), which continues to convert into furfural. Not limited to sulfuric acid, the statistic also shows that the researcher also mainly uses several other acids such as hydrochloric acid (HCl) [47], phosphoric acid (H₃PO₄), and nitric acid (HNO₃) for the pretreatment. Due to its ability to remove hemicellulose, acid pretreatments have been used as parts of overall processes in fractionating the components of lignocellulosic biomass [48]. Acid pretreatment (removal of hemicellulose) followed by alkali pretreatment (removal of lignin) results in relatively pure cellulose.

During the chemical pretreatment commonly, it will consist of the addition of concentrated or diluted acids (usually between 0.2% and 2.5% w/w) to the biomass, followed by constant mixing at certain temperature range (30–210 °C). The efficiency of the hydrolysis process of the sugar will last longer than minutes to hours due to the condition of the pretreatment. There are advantages and disadvantages of the acid treatment onto the biomass for the optimum conditions of operation. A key advantage of acid pretreatment is that a subsequent enzymatic hydrolysis step is sometimes not required, as the acid itself hydrolyzes the biomass to yield fermentable sugars. Hemicellulose and lignin are solubilized with minimal degradation, and the hemicellulose is converted to sugars with acid pretreatment. However, extensive washing and/or a detoxification step is needed to remove the acid before the biological process (fermentation step) takes place. Due to the corrosive nature and toxicity of most acids, an adequate material for the reactor is required in order to withstand the required experimental conditions and corrosiveness of the acids. Another drawback is the production of fermentation inhibitors like furfural and HMF (hydroxymethyl furfural) that reduces the effectiveness of the pretreatment method and further processes.

5.3.5.2 Green Solvent

The usage of ionic liquids (IL) and other solvents for the treatment of lignocellulosic biomass has attracted many researchers to involve with as it tunability of the solvent chemistry and hence the ability to dissolve a wide variety of biomass types. Basically, the ionic liquids are salts (consist of a small anion and a large organic cation), which exist as liquids at room temperature and have a very low vapor pressure. The history of the chemistry for the anion and cation can be tuned to generate a wide variety of liquids that can dissolve several biomass types—corn stover, cotton, bagasse, switchgrass, wheat straw, and woods of different hardness (pine, poplar, eucalyptus, and oak). The properties of IL and similar solvents like low vapor pressure make them more than 99% recoverable in several operations, thus reducing costs of solvent usage. Furthermore, since no toxic products are formed throughout the pretreatment operation and plus IL can be recoverable, the researcher recognized them as green solvents. Table 5.10 (adapted from the work of Sun and coworkers) lists the dissolving capacity of different celluloses by a variety of ILs. For an IL to be used in the pretreatment of biomass, it should not only have high dissolution capacity, but also low melting point, low viscosity, low/no toxicity, and high stability.

Table 5.10 Advantages and disadvantages of different pretreatment methods of lignocellulosic solid waste [38]

5.4 Developing an Energy from Waste Facility

5.4.1 Thermochemical

This section focuses on the thermochemical waste fuel technology as many conversion procedures (gasification or pyrolysis) demand a uniform feedstock. The technology analysis contains a process description, limits, and current and future applications. Environmental impact, energy balances, material regeneration, and mode of operation are the evaluation criteria (e.g., flexibility in dealing with input variation). Table 5.11 describes the different types of thermochemical treatment for MSW and where it falls under which category of treatment. An advanced thermal conversion system involving high-temperature gasification of biomass and municipal waste into biofuel, syngas, or hydrogen-rich gas is presented in this section. Figure 5.12 depicts the overall pretreatment available for MSW.

Table 5.11 Different types of thermochemical treatment for MSW [46]

Fig. 5.12

Overall of the pretreatment of the MSW [46]

5.4.2 Incineration

In comparison to pyrolysis and gasification, incineration has been widely accepted by countries around the world Table 5.12. The concepts of incineration are:

• 1. to treat waste by reducing the amount of its volume (oxidation of the combustible materials contained in the waste) and hazardous characteristics.

• 2. to capture or disrupt potentially harmful substances.

Table 5.12 Typical reaction conditions and products from pyrolysis, gasification, and incineration processes [46]

Besides that, the incineration processes can be a technology for energy recovery, mineral and/or chemical content of waste. In addition, this technology can be implemented in a wide range of wastes. The property of waste is highly heterogeneous, the composition mainly of organic substances, minerals, metals, and water. During incineration, flue gases are generated that contain most of the available fuel energy as heat. The organic waste substances burn when they have reached the ignition temperature and encounter oxygen. The actual combustion process takes place in the gas phase in fractions of seconds and simultaneously releases energy.

Figure 5.13 shows the flow diagram of WtE—from MSW to electricity through incineration.

Fig. 5.13

WtE—from MSW to electricity through incineration (APC stands for Air Pollution Control) [49]

5.4.3 Gasification

The other technology that falls under thermochemical is the gasification method. Gasification includes converting carbon-based compounds into a flammable gas (synthesis gas or syngas). The process takes place at a high temperature (500–1800 °C or higher) where several reactions between carbonaceous materials with air, oxygen, steam, carbon dioxide, and/or a mixture of these gases occur. Air gasification produces a low heating value (LHV) gas (4–7 MJ/Nm³ higher heating value), while oxygen gasification produces a medium heating value (MHV) gas (10–18 MJ/Nm³ higher heating value) [50]. The syngas contains CO₂, CO, H₂, CH₄, H₂O, trace amounts of higher hydrocarbons, inert gases originating from the gasification agent, various contaminants such as small char particles, ash, and tars [51]. A second-generation liquid biofuel can be made from syngas, which can be utilized to produce electricity and/or heat more efficiently. The gasification advantages presented in Fig. 5.14 while Fig. 5.15 illustrates the flow diagram of WtE—from MSW to electricity through gasification.

Fig. 5.14

Advantages of gasification technology

Fig. 5.15

WtE—from MSW to electricity through gasification [49]

5.4.4 Pyrolysis

Pyrolysis is thermal degradation (400–900 °C, but usually lower than 700 °C) either in the complete absence of an oxidizing agent or with such a limited supply that gasification does not occur to an appreciable extent (described as partial gasification) and is used to provide the thermal energy required for pyrolysis at the expense of product yields. Products from pyrolysis exhibit in Fig. 5.16 which the relative proportions of which depend very much on the pyrolysis method and reactor process parameters.

Fig. 5.16

Three products from pyrolysis

For MSW, the heating values of pyrolysis gas are typically between 5 and 15 MJ/m³, while for RDF, the values are typically between 15 and 30 MJ/m³ [51]. MSW to electricity process through pyrolysis process is shown in Fig. 5.17. Figure 5.18 depicts the basic pyrolysis process stages flow waste treatment.

Fig. 5.17

WtE—from MSW to electricity through pyrolysis [49]

Fig. 5.18

Basic process stages flow

5.4.5 Combination Processes

In the following subsections, we will look at a small number of different combinations of procedures.

5.4.5.1 Combination Pyrolisis-Gasification

In this section, two distinct types of pyrolysis-gasification combinations are discussed as different stages and processes that are directly connected. On most occasions, the waste must be dried and shredded before attempting to enter the first thermal phase. After pyrolysis, the metals and, if necessary, inert material may be discarded. Since pyrolysis gas and pyrolysis coke demand reheating during the gasification process, the technical and energy necessities are greater than for processes that are directly connected. Pyrolysis coke is decommissioned in two stages, with the first stage supplying gas to the second thermal stage, which is an entrained flow gasifier. On this level, both (metals and inert materials) can be removed from the pyrolytic coke. Pyrolysis gas is subsequently sent into the second thermal stage, which is an entrenched flux gasifier, coupled with the pyrolysis oil and the fine, solid fraction. During the entrained flow, at high pressure and at a temperature of 1300 °C, the oil and fine fraction are gasified, releasing carbon dioxide. To recover energy, the synthesis gas produced is cleaned and then combusted. Using a water bath, the solid remnants are melted down and filtered out, eliminating any remaining residue [51].

5.4.5.2 Combination Gasification-Combustion

The use of a fluidized bed gasifier in combination with a high-temperature combustor can result in the melting of ash. Shredding wastes, waste plastics, and MSW are gasified at a temperature of roughly 580 °C in an internally circulating bubbling fluidized bed. The material that is enormous in size is separated from the bed material at the bottom of the pile of material. The material from the bed is recycled back into the gasifier. In contrast, for fine ash, small char particles and flammable gas are delivered to the cyclonic ash melting chamber (to which air is injected to produce the desired temperature for ash melting, which is generally around 1350–1450 °C). The ash melting chamber is an integral feature of the steam boiler that is utilized for energy recovery. There are a number of other products produced by this method, including ferrous and nonferrous recyclable metals, a vitrified slag (which has reduced leaching hazards) and metal concentrates made from secondary ash, in addition to the power and steam.

When compared to other gasification processes, this one is clearly performed at atmospheric pressure and with the use of air (not rely on oxygen). Pretreatment of MSW with shredding is required in order to reduce the particle size to 300 mm in diameter. Wastes that already meet this criterion can be processed without the need for shredding. In addition to MSW, other wastes such as sewage sludge, bone meal, clinical waste, industrial slag and sludge are handled in the various plants currently in operation [52].

5.4.6 Plasma-Based Technologies

Plasma is referred to as the fourth state of matter since it exists in four different states at the same time. Because plasma is highly reactive, it behaves in a manner that is significantly different from that of ordinary gases, solids, or liquids. The formation of plasma comes from the process of gaseous molecules are forced into high energy collisions with charged electrons, resulting in the generation of charged particles. There are two energies required to create plasma either (1) through thermal or (2) carried by either an electric current or electromagnetic radiation. It is possible to distinguish two main groups of plasmas based on the energy source used and the conditions under which they are generated. The first is high-temperature plasmas, also known as fusion plasmas, in which all species are in a thermodynamic equilibrium state, and the second is low-temperature plasmas, also known as gas discharges [53]. This technology is quite new and at the emerging stage for the waste management. Overall, the primary advantages of the plasma it offers for waste treatment processes are high energy intensities and high temperatures: Fig. 5.19 shows the advantages of plasma’s process in WtE.

Fig. 5.19

Plasma’s advantages

5.4.7 Biochemical

5.4.7.1 Introduction

It is well known that abundant municipal solid waste (MSW) is an emerging biomass source where it can become the highest potential for large-scale second-generation bioethanol production. The biochemical process describes an efficient MSW to ethanol bioconversion process that comprises pretreatment and enzymatic hydrolysis, as well as precise quantitative information on the settings that maximize the glucose production to 80% following a 24-h hydrolysis reaction. In the biochemical conversion process, solid biomass waste is converted to ethanol by sequential steps of pretreatment (to reduce the recalcitrance of biomass), hydrolysis (conversion of sugar polymers to monomers), and fermentation (sugars to ethanol). Feedstocks were pretreated using three chemical pretreatments (dilute acid, dilute alkali, and hot water) and subsequently hydrolyzed enzymatically to investigate the effect of pretreatment and estimate the potential ethanol yields. Carbohydrate content in biomass is varied depending on the maximum cellulose content. All pretreatments are effective in increasing the hydrolysis yields and bioethanol yield. Besides that, the potential of this simplified compound also can contribute to the energy via the anaerobic process through the methanogenesis process, thus allowing the generation of methane gas.

5.4.7.2 Fermentation: Ethanol Production

Figure 5.20 introduces a fermentation flow diagram for methane production from municipal solid waste (MSW).

Fig. 5.20

Fermentation and methane production from MSW

This method can be separated into two steps with a focus on the enzyme hydrolysis process: long chains are hydrolyzed into soluble oligomers during the first stage and soluble oligomers are degraded into sugar monomers throughout the hydrolysis process. Several experiments revealed that some of the primary parameters important for limiting hydrolysis rate because of effects on enzyme binding and substrate access to cellulase enzymes include the physical property of cellulose such as crystallinity, degree of polymerization, and accessible surface area [54]. The hydrolysis of cellulose is influenced by the crystalline system as the glycoside linkages are difficult to hydrolyze in crystalline regions as compared with in amorphous parts [54]. The mode of the enzymatic hydrolysis on cellulose from various classes mode of an enzyme is presented in Table 5.13. Thus, from here, the simplified compound also can go toward the process of fermentation for bioethanol production (commonly using commercial yeast). The yeast will have enough supply of “food” as all the enzyme modes are functioning well; thus, the solid waste becomes very rich in nutrients and reflects the rapid growth of yeast. This reflects a higher biomass conversion to become new renewable energy, biofuel (bioethanol) (Figs. 5.21 and 5.22).

Table 5.13 Mode of action of enzymatic hydrolysis of cellulose by an enzyme from various classes during the fermentation and anaerobic process of lignocellulosic biomass from MSW [41]

Fig. 5.21

Generic process of bioethanol production from lignocellulosic waste from MSW

Fig. 5.22

Process flow diagram of bioethanol production from lignocellulosic waste (grass straw) from MSW

5.5 Reducing the Environmental Impacts and Maximizing the Energy

Climate change is the most severe environmental risk facing mankind and the world. Human activity is the source of the greenhouse gases that cause it. Carbon dioxide (CO₂) is the most significant of these pollutants since it raises average temperatures at the Earth’s surface, resulting in more severe weather events such as floods, droughts, and hurricanes, as well as increasing sea levels and damage to whole eco-systems. If we do not act quickly, the consequences for people all over the world may be disastrous.

To prevent harmful climate change, we must reduce CO₂ emissions globally over the next decade. We need to turn to sources of energy that do not emit CO₂—and there are plenty of them—in addition to doing whatever we can to conserve and use energy more efficiently. Renewable energy is derived from non-depleting sources such as the sun, wind, tides, waves, and plants. These renewable energy sources can be used to produce electricity without releasing carbon dioxide into the atmosphere. For example, the United Kingdom has committed to obtaining 20% of all energy (not only electricity but also heat and transportation fuel) from renewable sources by 2020. The United Kingdom’s contribution to this goal is 15%. We still have a long way to go to achieve this goal: green energy accounted for less than 2% of total UK energy in 2006.

As it is vital for the widespread use of fossil fuels, the primary source of many environmental pressures, a substantial amount of the fuels will be exhausted in the future. Thus, it appears as if a transition to renewable energy sources is needed. One downside to renewable energy is that it requires property, which is significant. But, for those who can deal with the investment in infrastructure, renewable energy is attractive. Environmental effects are not any more than earlier in the life cycle, in the building of the power plants, to be sure, but more important. To this end, on a note, one point, the justification for developing life cycle evaluation is that it is to do cost/reserve analysis such as to compare renewables with fossil power plants is to analyze trade-offs. The amount of work that has been done on the LCAs has focused on various renewable power technologies pales in comparison to that how many were done in the past.

The overall human population is increasing, but there are places where it is slower and places where it is accelerating, leading to a rise in energy demand. By 2035, it is expected that renewable sources will produce 66% percent of the electricity. This is because the majority of the world’s energy is nonrenewable, as shown in Fig. 5.23, according to [4].

Fig. 5.23

Shares of energy sources used in electricity production 2007 [4]. (Reuse by permission from Elsevier and Copyright Clearance Center)

Although energy is mainly used for heat and electricity, it can also be transformed into other ways. While the overall purpose of his work is to assess the environmental effect of renewable energy, only analyzing the output of electricity provides a consistent reference. Furthermore, as one of the most readily available and flexible electricity carriers today, it is gaining a larger market share in energy initiatives and scoring higher growth measures [4].

Resources such as fossil fuels and nuclear ores can be depleted at a pace that is millions of years for every year, which means they are now being consumed more rapidly than they can be replenished. This explains why there is a limited supply of non-capacity of nonrenewable energy, and hence why alternative energy sources must be used until they are not fixed or built-in if nonrenewable resources are depleted. Nations have turned their attention to rising energy efficiency as well as to renewable energy to address energy insecurity issues, the majority of which is related to climate change.

No fossil fuel reserves mean countries benefit from having higher energy security and clean energy solutions because these renewable resources are known to be fully environmentally friendly [55]. Renewable energy supporters, on the other hand, believe that this low-density, low-efficiency technologies will never be viable. Scientists have also often contended that the low output of fossil fuels such as coal and nuclear are not competing with renewable energy sources such as solar and hydroelectric.

The desire to increase the environmental efficiency of energy systems is unquestionable, but whether renewable systems are superior to nonrenewable systems must be resolved. Since they produce less greenhouse gases than conventional energy, renewable energy technologies are praised for their capability of supplying abundant amounts of power. This factor should also be factored into future studies: on the many instances where natural and artificial causes are blamed for a wide-ranging environmental impact, including ozone depletion, acid rain, toxins and carcinogens, as well as lesser impacts such as habitat degradation, consequently, we also need to examine more environmental variables in depth. So, energy is being used at an exponential rate and accelerating; it is imperative that energy policymakers have a profound understanding of the total consequences of the implementation of new technology.

The whole scientific community is commonly agreeing that bio componence is renewable energy. This fertilizer will cause the plant to emit a significant amount of CO₂ throughout its cycle, which will be offset by CO₂ it takes over the life of the course of the plant to grow biomass. According to some research, it appears that removing all that vegetation results in more carbon storage, such as carbon sequestration, than that achieved with the addition of more vegetation. Furthermore, the decomposition of the vast carbon contained in wood occurs in the short time that it takes for trees to die and be decomposed, which causes much more global warming than a longer period of which could result in the release of more carbon. Organic matter emits only about half the sulfur dioxide as carbon dioxide when combusted, so organic combustors have lower sulfur dioxide emissions than their fossil fuel alternatives.

Biomass may be transformed into various forms of energy; it may be combusted, such as hydrocarbon or gaseous, or it may be converted to aqueous or to liquid or gaseous fuels. For thousands of years, traditional biomass use has included the use of biomass for space heating and cooking. Due to this, there is a significant amount of air pollution as wood is used in open air, there is a concern with the abundance of air emissions from pits and fireplaces in undeveloped regions. Particulates, volatile organic compounds (such as benzene, toluene, and t-butyl hydroperoxide), and dioxins, which are produced when incomplete combustion occurs in the contaminants (for example, due to either gas leakage or breakdown) [56]. More recently, these contaminants have become of environmental as well as health importance due to the lack of pollution controls.

Simultaneously, most of the municipal solid waste is made up of biodegradable components, such as food wastes, paper wastes, and yard wastes. These wastes are treated using a specially designed furnace, which simultaneously dries and burns them at the same time. The primary objective of a power plant is to produce steam, which is then used to drive a turbine, which generates electricity. Most municipalities are not significantly benefited from dealing with their solid waste because solid waste management has the additional advantage of sequestration, which makes it not increase their total power use, not to mention the conservation of energy.

Biomass can be converted into liquid fuel, which yields ethanol as a byproduct. More ethanol will be produced by fermenting biomass in the form of carbon-rich materials such as animal wastes, or dung in the anaerobic decomposition process. Before the ethanol can be used in engines, it must be separated from water and dried. Conventional fossil fuel, that is, gasoline, is widely used with biomethane to maximize fuel efficiency and minimize the effect on the atmosphere, a mixture of bioethanol and biomethane, to maximize the fuel and minimize the environment. Bioethanol has been added to the petrol, making the whole mixture more combustible, increasing oxygen content, thereby making it easier to combust completely and cutting down on CO₂ emissions.

Anaerobic degradation of industrial sludges, crops, animal waste, and domestic sewage may generate biogas and digestate that can be used as fertilizer. Carbon (carbon dioxide is the majority) and methane (CH₄) are the three components of natural gas. They may also be present, including a few different elements, as well as ammonia and sulfides. Therefore, the chemical composition of the biomass and the digestibility of the biomass would influence the ratio of methane to carbon dioxide in the two gases that are formed.

Using waste as a base for biogas or biomass combustion plants will result in even more greenhouse gas (GHG) reductions. The reduction of GHG emissions aids in the stabilization of the global environment. As a result, biogas and biomass combustion processes provide a significant advantage over fossil-fuel-based energy production. The cleaning and sanitation effect of biogas plants has significant positive environmental and health effects. Fermentation eliminates odors and allows the substrate to be treated more easily. Biogas technology will save money in the medical sector and improve people’s health by virtue of this sanitation impact. Another significant environmental effect may be caused by biomass transportation. External consequences of transportation include air pollution and noise. This negative effect should be held to a minimum for environmental and social purposes.

5.6 Recovery Energy from Waste: Global Development

The world’s population is rapidly urbanizing and industrializing, posing substantial challenges such as escalating energy demand, massive waste production, and environmental degradation. The waste-to-energy nexus created on the 5R concept (Reduce, Reuse, Recycle, Recovery, and Restore) is crucial in unraveling these Gordian knots. Socioeconomic development has caused a rise in solid waste production. Most municipal solid wastes (MSW) are non-biodegradable and take longer to degrade into natural compounds. MSW includes organic matter, plastics, metals, glasses, textiles, wood, rubber, leather, and paper, all of which come from domestic, commercial, or industrial sources [57]. The rate of waste produced in different countries around the world has been influenced by economic conditions and living standards. The sharp rise in MSW per person from 0.5 to 1.7 kg shows the gravity of the situation. Undeniably, around the world, the rate of waste accumulation is outpacing the rate of suburbanization. Annual MSW output is currently around 1.3 billion tons or about 1.2 kg/person/day. This figure is projected to reach 2.2 billion tons by 2025, or 1.42 kg/capita/day [58]. MSW output is estimated to achieve 9.5 billion tons by 2050 [59].

In developing countries like India, MSW generation is increasing at a rate of 1.3%/year, suggesting an increase in public socioeconomic standards. India currently produces about 90 million tons of MSW per year, with per capita waste generation estimated at 0.37 kg/day [60]. Furthermore, nearly 94% of waste is thrown out perilously in open dumps with no segregation, with 70–75% of it being organic matter [61]. In 2016, China, the world’s most populous nation, generated 234 million tons of MSW [47]. MSW generation rates are 1.34 kg/capita/day, 2.13 kg/capita/day, 2.00 kg/capita/day, 0.09 kg/capita/day, and 0.58 kg/capita/day in the United Kingdom, the United States, South Africa, Ghana, and Nigeria, respectively [48].

Agriculture is important to the global economy, contributing 33% of the global GDP and employing 26.81% of the global workforce, with agricultural land accounting for 38.14% of all land [62]. Residues from farming fields, animal waste, and agro-industrial effluent are all examples of agricultural waste. Over 3 billion tons of agricultural waste are produced annually around the world, with India producing more than 600 million tons [62]. Besides the panicle residue after harvest, rice grains contain >50% non-edible biomass, including roots, blades, and sheaths. Rice straw is grown worldwide in approximately 731 million tons, and 126.6 million tons are produced in India alone.

The Electricity Act of 2003 was passed in India’s parliament, stressing the importance of rapid electrification of un-electrified villages. Owing to economic restrictions and difficult terrain, supplying energy from large coal-fired power plants is not always feasible. Furthermore, the number of customers in many places is extremely low. As a result, electrifying these villages with grid power is not cost-effective. In such areas, solar power is more significant. The Jawaharlal Nehru National Solar Power Mission was established as a result, with the aim of installing 20,000 MW of solar power by 2022 and reaching grid parity by the same year. As a result, solar power output in India is driven by international standards requiring a lower carbon footprint and rapid rural electrification. Different Indian states have implemented solar energy policies based on supply convenience and other socioeconomic factors in accordance with national policy.

Aside from rural electrification, the Indian government has implemented a range of policies to establish renewable energy policies to meet international carbon emission reduction commitments. Furthermore, small and un-electrified villages in India are not suitable for grid electrification due to poor economic conditions and difficult terrain. As a result, policymakers started to think about distributed generation using local resources. Until now, thermal power from large coal-fired power plants dominated the Indian power sector. The share of power generated by various resources in the Indian grid is depicted in Fig. 5.24.

Fig. 5.24

Share of different energy sources in electricity generation in India

Jamaica’s energy requirements, on the other hand, are largely dependent on imported petroleum. Around 91% of the country’s electricity is imported, with the rest coming from renewable sources. The rising cost of global oil, combined with the local necessity for fuel and a shortage of monetary resources to finance an ever-escalating oil bill, forces Jamaica to investigate alternative energy sources as soon as possible. In its National Energy Policy 2009–2030 and Vision 2030 Jamaica—National Development Plan, Jamaica is setting goals for renewable energy (20% by 2030) and energy supply diversification (70% by 2030). The National Energy from Waste Policy will assist in achieving these goals.

Jamaica outperforms most Caribbean countries in terms of renewable energy production. Wind, small hydro, solar, and biomass (primarily fuelwood, sugar cane ethanol used in E10, and bagasse used in cogeneration facilities) account for 9% of the country’s energy mix. The involvement of various sources in the total amount of renewable energy is depicted in Fig. 5.25. Bagasse, a sugar cane waste product, accounts for more than a third of the country’s renewable energy sources. Utilizing a variability of technologies, such as municipal solid waste incineration, landfill gas capture, biodiesel production, biogas production from animal waste, and wastewater sludge production, Jamaica may increase its contribution and expand energy-from-waste projects based on other types of waste. This policy establishes the foundation for further research, growth, and expansion of these possibilities.

Fig. 5.25

Contribution of different sources for renewable energy in Jamaica

In China, public-private partnership (PPP) waste-to-energy (WTE) incineration has seen instant development to manage sustainably and effectively due to the increase in the amount of municipal solid waste (MSW). After the execution of China’s “Reform and Opening” policy in 1978, several significant economic and social milestones have been achieved. In 2019, China overtook the United States as the world’s second-largest economy, with a GDP of CNY 99,086.5 billion (USD 14,015.1 billion) and a per capita GDP of CNY 70,892 (USD 10,027). A rising number of people have been moving from rural to urban areas because of the country’s rapid industrialization, resulting in an ever-increasing urbanization trend. At the end of 2019, China’s total urban population was 848.43 million, representing a 60.6% urbanization rate [63].

MSW generation has increased significantly because of prompt industrial development and suburbanization, as well as shifts in expenditure patterns because of rising living standards. According to the Asian Development Bank, China is the world’s second-largest producer of MSW. The annual volume of MSW increased from 155.1 to 228.0 million metric tons, as shown in Fig. 5.26 (an annual rate of 3.1%) between 2004 and 2018, while the annual number of harmless-treated MSW increased from 80.9 to 225.7 million metric tons (an annual rate of 11.9%).

Fig. 5.26

MSW collection and treatment in China [63]. Reuse by permission from Elsevier and Copyright Clearance Center

Even though China’s annual MSW volume is less than that of the United States, its growth rate is significantly higher. According to Cui et al. [63], China’s average annual MSW growth rate is 6.2%, while the USA’s is just 1%, meaning that China will overtake the USA as the world’s largest MSW generator by 2021. Meanwhile, China’s MSW production per capita is less than a third of that of the United States and even less than that of other Asian countries, implying that China’s MSW output will increase.

Additionally, as the economies of the EU’s member states expand, the EU must resolve waste generation issues. With 392 million tons of urban solid waste, the EU is officially ranked second in the world [64]. Over the last two decades, the production of municipal solid waste in the EU has gradually increased [65]. In 2014, the EU initiated the Seventh Environmental Action Plan (EAP) to promote a circular economy and decrease the adverse impact of urban waste on the environment. According to the EAP, reducing solid waste to at least 65% of current levels would help the 2030 target of “zero waste emissions” be met.

Since technology helps reduce pollution, it necessitates the use of more resources (including production factors) and electricity. Because of technical solutions, filters or dilution may result in waste. As a result, the rate of recovery is slow, even though most of the waste generated in the EU is managed using various technologies. Meanwhile, waste generation is regarded as a critical factor in the renewable energy-economic growth nexus. However, current waste-to-energy plants perform poorly in terms of heat recovery, and efficient incineration capacity in the EU is regionally concentrated [66].

Material life spans are shortening as technological advancement accelerates, resulting in increased waste generation. The toxicity of mobile phone waste, for example, has ascended because of technological advances. This has yielded several positive outcomes, such as the production of recycled materials and boosted energy usage. However, novel recycling strategies must be established to address a variety of waste sources and landfills. Prior research has established the critical role of R&D capabilities in boosting economic growth [67]. In the BRICS countries, for example, increased R&D intensity helped to decouple economic growth from CO₂ emissions.

The current study by [66] adds to the growing body of evidence that urban waste generation and economic development have a long-run equilibrium relationship. The long-term bidirectional connection exists between municipal waste production and R&D rate, as well as municipal waste production and heating energy performance. For regions of former EU member states, there was a positive bidirectional causal relationship between municipal waste generation and GDP, but for regions of new EU member states, there was only a unidirectional long-run effect running from GDP to municipal waste generation. These findings suggest that in the short term, bidirectional causality exists for both types of regions. These results, taken together, illustrate the importance of decentralized waste policies and have significant consequences for national and regional policymakers.

Every year, tens of thousands of waste management facilities are planned and constructed throughout the United States. The US Environmental Protection Agency (USEPA) reports that well over $100 billion is spent on environmental protection per year, with virtually all of it going into waste management to improve and protect water, air, and land from contamination. This amounts to about 2.5% of the US total household product, up from 0.9% in 1972. Public support for waste management spending is high. In the year 2000, 64% of Americans expressed “extreme concern” about soil, water, and hazardous waste pollution. Most Americans are unwilling to compromise environmental security to increase job creation and regional GDP. In 1984, 61% of Americans said that environmental conservation was more important than economic development. The percentage was 67% in April 2000.

While the advantages of clean, renewable energy and fuels are obvious, renewable energy resources have only replaced fossil fuels at a very slow pace in the United States over the last 30 years. Despite significant investments in developing and scaling up renewable energy technologies, an integrated, large-scale renewable energy industry has yet to emerge in recent times. The fuel ethanol industry in the United States is the nearest referent to this type of industry. While corn feedstocks account for the majority of US fuel ethanol capability, total production only meets a small portion of national motor fuel demand [68]. Marketable renewable energy resources have not been broadly presented for a variety of reasons: The economics of stand-alone processing systems and plants have historically been unfavorable, funding for novel processing systems and plants has been difficult to secure, transportation and supply facilities are lacking, and long-term competition from fossil energy. However, with the passing of time, an unforeseen corporate environment has emerged, which could propel the renewable energy industry forward. Regrettably, the US energy economy’s uncertainty has continued to obscure the events that contributed to this situation.

To boost the use of renewable energy, the US government also passed the Energy Policy Acts in 2005 and the Federal Energy Independence and Security Act in 2007. The United States promotes renewable energy consumption (REC) use (REC) to minimize reliance on oil, mitigate the harmful impact of energy price shocks, and fight global warming. The country makes extensive use of biomass and hydropower. In 2018, the REC in the United States included hydropower (23%), wind (22%), wood (21%), biofuels (20%), solar (8%), waste (4%), and geothermal (4%). The intake of biomass accounts for 45% of total REC. In the last decade, the US REC has risen by 112%. The proportion of renewable energy in the overall energy mix is expanded to 27% [69]. Figure 5.27 depicts the evolution of REC outlets in the United States over the last 10 years. The use of hydropower resources has remained constant. There is also a limit to the rise in geothermal and waste use. However, consumption of solar (1072%) and wind energy (244%) expanded dramatically following the 2008 financial crisis. Subsequent to these energy sources, wood and biofuels have seen fairly modest rises.

Fig. 5.27

Disaggregated Renewable Energy Consumption from 2009 to 2018 [69]. (Reuse by permission from Elsevier and Copyright Clearance Center)

Meanwhile, Malaysia has been committed to renewable energy production since 2001 to diversify energy supplies for electricity generation while adhering to the market force theory. However, previous attempts had failed, and the government concluded that the business-as-usual strategy is incompetent and ineffective for long-term growth. Considering the important lessons learned from the previous strategy, the Malaysian government developed a successful policy known as the National Renewable Energy Policy and Action Plan in 2008 to confirm a comprehensive approach for Malaysia’s renewable energy industries. The policy seeks to increase the use of renewable energy in the national electricity supply mix while also promoting long-term socioeconomic growth. The policy also emphasizes the importance of a comprehensive research and development (R&D) program and human capital development to accelerate the growth of the renewable energy industry, thus stimulating economic benefits through the development of innovative goods and services [70].

The introduction of a structural R&D program is critical because it will contribute to the local production of pioneering commodities and services, which will help Malaysia’s renewable energy industry expand more quickly. Furthermore, by making clean energy technologies cheaper and simpler to use, the local innovation process would aid in its diffusion. As a result, the competitiveness of local companies will be strengthened. The percentage of growth in the use of renewable energy technology, the steady decrease in fossil fuel usage for electricity generation, and the reduction of CO₂ emissions are all observable outcomes of Malaysia’s R&D program’s significance.

The Renewable Energy Act of 2011 was passed to put in place the Feed-in Tariff (FiT) scheme for increasing renewable energy power generation in Malaysia. Biogas, biomass, mini hydro, and solar photovoltaic (PV) are the four renewable energy options eligible for the FiT. Renewable energy manufacturers may be landholders, company owners, private investors, or even farmers under the FiT mechanism. With their generated device or technology, this process can be reimbursed for renewable energy. The Renewable Energy Fund (RE Fund) guarantees payments to renewable energy suppliers, also known as Feed-in Approval Holders, for a period of 21 years for solar PV and small hydropower, and 16 years for biogas and biomass.

The government’s efforts were bolstered in the current Eleventh Malaysia Strategy, which included plans to increase renewable energy staff capability and introduce net energy metering (NEM). In 2015, the government made a huge effort to achieve 1% of electricity produced from renewable energy in the energy mix, as shown in Fig. 5.28. Through these measures, renewable energy installed capacity rises by more than 20%, including off-grid construction and cogeneration. Given the massive support earned by the Malaysian government, renewable energy would play an important role in the energy mix and address environmental challenges in the future (Fig. 5.29).

Fig. 5.28

Power generation of commissioned renewable energy installations in Malaysia [70]. (Reuse by permission from Elsevier and Copyright Clearance Center)

Fig. 5.29

Malaysia’s target of renewable energy and CO₂ prevention [70]. (Reuse by permission from Elsevier and Copyright Clearance Center)

According to a study by M. Chachuli et al. [70], one of the driving forces behind Malaysia’s renewable energy generation is the implementation of the FiT scheme. This form of implementation has had a gradual impact on Malaysia’s R&D activity in the field of renewable energy resources. A systemic R&D program and a group of professionals will help drive the development of renewable energy industries by developing innovative products and services. Both initiatives will help spread clean energy technology by making it more efficient and affordable. This change will influence renewable energy industry players and will help the country economically. Renewable energy industries in Malaysia can be evaluated holistically for their practicality and economic viability. Furthermore, the government must concentrate on R&D endeavors to ensure the environment’s long-term viability and to help the country’s socioeconomic growth.

5.7 Summary

Waste generation is estimated to expand rapidly in the coming years in developed and emerging countries. Energy-generating incineration can be a key element of sustainable waste management to ensure the safe disposal of this waste [71]. The fascinating way to reclaim energy from waste is to generate either electricity or CHP, using the conventional but recognized MSW incineration. It is important for any current landfill because of the environmental advantages of the extraction of biogas. Further research would be needed to explore additional technologies that could be of interest to WtE projects, such as plasma arc gasification and thermal depolymerization. If properly managed, solid waste can be a source of employment, jobs, and profits. To reduce the amount of non-degradable materials that include waste paper, metal, glass, plastic bottles, and used tires, the private sector and investors are encouraged to develop solid waste recycling systems.

As far as policy implications go, the government should put in place policies that will promote renewable energy consumption (REC) in the long run. The government will contribute to energy protection and sustainability in this manner. Since REC involves unit root, it has the potential to have a spillover impact on jobs, economic development, capital stock, and other significant macroeconomic variables. Energy incentives and recycling policies, on the other hand, have had a little long-term effect on hydropower and biofuels energy consumption in the world. Past patterns in hydropower and biofuels can be used to predict future movements. A negative shock in hydropower and biofuels energy demand has only a short-term effect. As a result, the government should refrain from intervening in these forms of energy use unless it is appropriate.

Like Malaysia, which has a controlled electricity market, the Feed-in Tariff (FiT) program’s funding sources are constrained to a fixed percentage levied on electricity bill owners. The ceiling scheme is essential to ensure that sufficient funds are available to pay renewable energy generators their FiT payments. When Malaysia’s electricity market is liberalized, or when a new system with a better solution is implemented in the future, the cap may be removed. Based on current R&D activities carried out in Malaysia, the installed facility of renewable energy resources, especially solar PV, biomass, biogas, and mini hydro, should be expanded. However, due to several constraints, including a lack of power and low wind speed in Malaysia, the result is not applicable to wind energy. Due to limited resources, producing many outputs from any renewable energy source is usually difficult. To speed up the deployment of renewable energy in Malaysia, additional incentive programs must be created. Overall, more effort is needed to achieve superior efficacy in R&D activities in Malaysia’s renewable energy production.

The study reveals an increasing global trend toward renewable energy output, with a focus on WtE technologies. The bio-methanation technology, with its relatively higher efficiency and lower capital and operating costs, is found to be the most cost-effective of all the WtE technologies considered. Because of its higher process efficiency and lower environmental emissions, RDF has a high potential for growth and is preferred over incineration. RDF, on the other hand, has drawbacks in terms of initial capital and operating costs, as well as labor capability requirements. The demand for power generation from these WtE technologies is enormous, and if firmly established, it will not only lead to power generation from renewable sources but also reduce landfill costs and related environmental issues.

Glossary

Blackwater

Water used to flush toilets, along with the human waste it flushes away.

Calorific Value

The calorific value of a substance is known as the number of calories produced when a unit amount of substance is fully oxidized. This value is measured using a bomb calorimeter. The calorific value of coal is calculated using the gross calorific value (HG), which includes latent heat of water vaporization.

Fossil Fuel

Coal, petroleum, natural gas, oil shale, bitumen, tar sands, and heavy oils are all examples of fossil fuels. All are carbon-based and were created because of geologic processes operating on the remains of photosynthesis-produced organic matter.

Greywater

Wastewaters from drains, tubs, showers, dishwashers, and clothes washers.

MSW

Municipal solid waste (MSW) is classified as waste collected by the municipality or disposed of at a municipal waste disposal site. It includes residential, agricultural, institutional, commercial, and municipal waste, as well as waste from construction and demolition.

RDF

Refuse-Derived Fuel (RDF) is made from domestic and commercial waste, which contains both biodegradable and non-biodegradable materials. Non-combustible materials such as glass and metals are removed, and the resulting residue is shredded. At waste-to-energy recycling plants, refuse-derived fuel is used to produce electricity.

SRF

Solid Recovered Fuel (SRF) is a high-quality alternative to fossil fuels made primarily from commercial waste such as paper, card, wood, textiles, and plastic. Solid recovered fuel has been further processed to increase its consistency and value. It has a higher calorific value than RDF and is used in cement kilns and other similar facilities.

Waste-to-Energy

Waste-to-energy (WtE) or energy-from-waste (EfW) is a term that refers to the method of producing energy in the form of electricity and/or heat from waste that has been sorted or processed into a fuel source. WtE is a method of reclaiming resources.