Keywords

1 Introduction

Plastic is a material whose characteristics favor its application in different sectors, as reflected in the increasing levels of sales reported annually by this industry. Most plastics are of synthetic origin, that is, they are synthesized from raw materials from gas or oil. However, in recent years, the environmental commitment has motivated the development of new materials from raw materials that are sustainable. One option is waste of agro-industrial origin, which, being organic in nature, has a wide variety of useful compounds for obtaining biomaterials. In this regard, there are some investigations where the use of some agro-industrial waste is recorded to obtain bioplastics. This, in addition to being a solution to the environmental problems caused by these wastes, is an alternative for their revaluation in the framework of the circular economy and the bioeconomy.

2 Consumer Society Versus Sustainable Production

Since the industrial revolution and up to the present, scientific and technological advances have made possible the development of new products to meet the needs of consumers. Today there is a great variety of articles on the market, in different brands, models, and prices, accessible to most of the population. But this wide variety of available products, together with the concept of planned obsolescence adopted as a commercial strategy in almost all value chains, has fostered the establishment of consumer societies.

The creation of a fast-fashion society, controlled by the different types of obsolescence, leads to improve the characteristics of new products concerning for to their predecessors (function obsolescence), to design products that wear out shortly after the end of a minimal warranty (planned obsolescence) and systematically educating consumers to appreciate the newest as the best (obsolescence of desirability), leads to disposable patterns of behavior, accelerates resource depletion and contributes to pollution environmental (Hellmann & Luedicke, 2018). The rise of these consumer societies has made the tendency to reuse objects that have already served their usefulness disappears, which in some way is a way to value them and reduce the rate of waste generation (Kedzierski et al., 2020).

This consumer behavior beyond generating sales revenue, makes manufacturers become environmental aggressors, by progressively requiring more resources to meet the demands of their production processes. Man has been based on the consumption of this material, first experimenting with natural polymers, horn, waxes, natural rubber, and resins, until the nineteenth century, when the development of modern thermoplastics began (Andrady & Neal, 2009). Worldwide, the per capita consumption of plastic was 11 kg in 1980, 30 kg for 2005, and it was estimated that it was 45 kg for 2015; with greater participation for the countries of the NAFTA zone and Western Europe with a per capita consumption of 139 and 136 kg, respectively (PlasticsEurope, 2008).

Since its inception, the plastics industry has been in constant growth, registering for the year 1950 a production of 1.5 million metric tons (MMt) and for the year 2018, a total of 359 MMt produced (Statista, 2020). In recent years, this increase is influenced by single-use plastics, invented for modern society with the purpose of use and disposal, whose main application is food packaging, shopping bags, or disposable tableware (Chen et al., 2021). Both the production and consumption of this material contribute greatly to environmental deterioration, not only due to the number of fossil resources required for the manufacturing process but also due to the various pollutants that are released into ecosystems during disposal end of wastes of this type and their prolonged permanence in them, given their slow degradation process.

In the face of existing environmental pressures and the face of imminent climate change, international commitments have been made in favor of the planet. An example of this is the Sustainable Development Goals (SDGs) of the 2030 Agenda, where at least seven of them directly or indirectly address environmental issues. Specifically, objective 12 of responsible production and consumption aims to decouple economic growth from environmental degradation, while increasing resource efficiency and promoting sustainable lifestyles (ONU, 2018).

A strategy related to the above is the adoption of new economic models focused on circularity and the use of raw materials of biological origin, to obtain new products. Within this approach are bioplastics, which are defined as a plastic that is bio-based, biodegradable, or that meets both criteria (European Bioplastics, 2018), and given their characteristics, they offer the possibility of introducing an alternative to the problems caused by conventional plastics.

A bio-based plastic is obtained totally or partially from biomass (Fig. 1). It includes starch, cellulose, proteins, lignin, chitosan, polylactic acid (PLA), and polyhydroxyalkanoates (PHAs)/polyhydroxybutyrates (PHBs). A wide variety of biomass of plant origin (complete plants or their residues, wood, dry grass) or animal (for example, bird feathers) is used for its manufacture, which is a resource with great potential to be used, rich in carbon, capable of being processed by microbial methods, for the production of bio-based polymers, a mixture of biopolymers and various chemicals (Brodin et al., 2017a; Maraveas, 2020). The main bio-based plastics that are currently marketed are thermoplastic starch (TPS), polylactic acid (PLA), polyhydroxyalkanoates (PHAs), polyethylene (bio-PE), propylene (bio-PP), and polyethylene terephthalate (bio-PET) bio-based, containing at least some renewable carbon (Lackner, 2015).

Fig. 1
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Types of bioplastics

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For a plastic to be biodegradable, it must decompose by the action of microorganisms or suffer a decrease in its molecular weight due to biological activity, producing CO2, H2O, CH4 (depending on the environment in which it is carried out), mineral salts, in addition to biomass (Reddy et al., 2013; Vert et al., 2012). It should be noted that the biodegradability of the material does not depend on the source of origin but the structure of the polymer. That is why there are biodegradable plastics of natural origin, synthesized from renewable resources and petroleum-based, but there are also bio-based nonbiodegradable plastics (Jiang & Zhang, 2017; Reddy et al., 2013).

The development of new bio-based materials under this bioeconomic model represents an important factor to achieve the sustainable growth of the bio-based plastics industry, which are also biodegradable. Sustainable development in any industry requires adopting changes in the processes, in the type and quantity of the resources used, in the treatment and control of the waste generated, as well as in the products obtained (Krajnc & Glavic, 2003). The bio-based industry and with it the production of bioplastics must also take care of its resources, processes, and waste, for sustainable production.

The use of monomers obtained from lignocellulose biomass as a replacement for those based on petroleum constitutes a point in favor of sustainability as it is an abundant and biodegradable renewable resource. Specifically, lignocellulosic biomass is present in energy crops, marine biomass, forestry, as well as forestry, agricultural, agro-industrial, industrial, and municipal solid waste (Al-Battashi et al., 2019). In this particular, the use of lignocellulosic waste is of special interest for its recovery through the obtaining of various products, one of them being bioplastics.

Regarding transformation processes, the production of bioplastics is carried out mainly by fermentation routes through biotechnological procedures, generally expensive and with a low performance from an industrial point of view. Efficient processes are required for the fractionation and purification of biomass, cost-effective routes for conversion to monomers and platform molecules (Brodin et al., 2017b), in addition to low-cost substrates, which could include some waste generated in the agro-industry.

Some pretreatments of lignocellulose biomass incorporate the use of steam or dilute acids and subsequent enzymatic treatments to break it up into simpler sugars. Although it is a practical approach, it represents economic limitations in large-scale processes. An important advance in the bioplastics industry is the development of a new bioprocessing system, which uses thermophilic microorganisms for the one-step conversion of lignocellulose into polyhydroxyalkanoate (PHA), excluding the chemical and enzymatic pretreatment steps (Govil et al., 2020).

Another consideration in the sustainable production of bioplastics from lignocellulosic waste is the energy requirements of the process. To reduce the consumption of public services in this area and satisfy the total heating requirements, an integrated process is proposed that takes advantage of the calorific value of the total biomass waste, the biogas generated by the wastewater treatment, in addition to a network of heat exchangers between hot and cold process streams (Kim et al., 2020).

Regarding the generation of waste, it is expected that bio-based plastics have a reduced carbon footprint about those produced from oil since they are in complete harmony with the rates and the time scale of the biological carbon cycle (Narayan, 2011). However, it should be considered that the use of food crops such as corn, sugar cane, rice, etc., in addition to competing with the population’s food needs, represents a threat to the total substitution of plastic containers of fossil origin by bioplastics, since according to the evaluation of the impact of the life cycle of bioplastics in terms of greenhouse gas emissions and land and water environmental footprint, it would represent a considerable increase in the use of land and water (Brizga et al., 2020).

Waste treatment must address the degradation routes available for the bioplastic generated. Although there is the possibility of using mechanical recycling, or using chemical treatments, including hydrolysis, pyrolysis, or alcoholysis, to depolymerize bioplastics such as polylactic acid (PLA) and thus generate value-added products, biodegradation is one of the most discussed aspects for this type of material. In this topic, it is important to define the environmental conditions necessary to ensure the decomposition of the biopolymer. There are specific conditions such as temperature, humidity, presence of microorganisms, that favor or counteract this biological reaction.

To achieve sustainable and economically attractive production, biomass should not be wasted under any circumstances, but rather should be used in a closed loop so that all waste streams are reintroduced into the value chain with a new function (Márquez Luzardo & Venselaar, 2012). Figure 2 shows the aspects to consider for the sustainable production of bioplastics.

Fig. 2
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Aspects in the sustainable production of bioplastics

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3 Valorization of Agro-Industrial Waste

Agro-industrial waste such as husks, seeds, whey, waste liquids, molasses, bagasse, among others, are generated in the processing of agricultural products (Panesar et al., 2015). The harvest is also part of the food production (Pfaltzgraff et al., 2013), therefore, the waste generated at this stage can be included within the agribusiness supply chain.

The Food and Agriculture Organization of the United Nations (FAO) in its record of burning crop residues, reported that in 2018 alone, about 460 MMt of dry biomass from four crops (rice husks) were burned, sugar cane, corn, and wheat), worldwide (Food and Agricultural Organization of the United Nations, 2020). All this available biomass, instead of being burned, could be used under a cascade economy model, to obtain a wide variety of products. The efficient use of biomass from both an ecological and economic point of view assumes that it must be used mainly in high-cost and low-volume applications, and then use the residues at a next level in applications, until reaching those of lower value and large volumes (Márquez Luzardo & Venselaar, 2012).

Agro-industrial waste with a high production rate throughout the world, in addition to being biodegradable, has great potential as a primary or secondary raw material for the production of biopolymers, as they are rich in useful substances (such as fermentable sugars, carbohydrates, lipids, polysaccharides, pigments, and aromatic compounds) (Heredia-Guerrero et al., 2017; Panesar et al., 2015; Ranganathan et al., 2020). However, they are rarely recovered and, on the contrary, are disposed of without any type of control, generating damage to the environment and economic losses (Beltrán-Ramírez et al., 2019; Bilo et al., 2018).

From the lignocellulose material present in some food waste, cellulose, and hemicellulose fractions can be extracted (De et al., 2020). Also, agro-industrial waste rich in starch has the potential to be used in obtaining thermoplastic starch, polyhydroxyalkanoates, and PLA (Chan et al., 2021; Grewal et al., 2020; Tsang et al., 2019). Residues from banana, rice, corn, and cassava have shown the presence of compounds of this type, useful in the production of bioplastics (Table 1).

Table 1 Characterization of residues
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As in synthetic polymers made up of a chain of monomers, a starch polymer (composed of amylose and amylopectin) is made up of chains of sugar monomers connected by glucosidic bonds. Thus, bioplastic is a polymer made up of simple sugars and can be synthesized from bio-based materials. Starch-based bioplastics are a promising substitute due to the abundance, renewability, sustainability, and biodegradability of this compound (Samer et al., 2019; Shafqat et al., 2020). PLA, PHAs, and polybutylene succinate (PBS) are promising bioplastics with bio-based raw materials and biodegradability properties that are produced by bacterial fermentation of sugars from carbohydrate sources (Changwichan et al., 2018). On the other hand, lignocellulosic fibers have also been studied as reinforcing material in bioplastics, exhibiting properties that are compatible with the polymeric matrix and thus the possibility of replacing synthetic fibers in bioplastics (Yang et al., 2019).

The trend of agricultural waste as a source of bioplastics production is increasing due to the amount generated per year, its low cost, and availability. The limitations of use are related to the lack of standardized definitions for the management of food waste, the scarce information regarding the quantities generated and the low production performance compared to the food raw material. The outlook for the use of agricultural waste as a raw material in bioplastics is expected to improve, with the advancement of biotechnology, product life cycle analysis, prioritization of value chains, investments in a future circular economy, and the intervention of the government with the establishment of legislation that favors its use (Chan et al., 2021; Teigiserova et al., 2019).

4 Biorefineries and Transformation Processes

A biorefinery is an industrial facility (or network of facilities), which use a combined set of technologies and conversion routes, to use the available biomass comprehensively and sustainable, to simultaneously produce biofuels, energy, materials, and other chemicals with added value (Morais & Bogel-Lukasik, 2013). It consists of an industrial complex that emulates the processing carried out in a traditional refinery, but unlike this one, instead of using oil as raw material, it uses biomass from different sources.

Currently, most of the biorefineries operating and under construction are located in North America and European countries (IEA Bioenergy, 2021). Although it is a relatively new production model that is still under investigation, interest in its implementation increases every day given the need to replace fossil resources with others of renewable origin.

The main objective of biorefineries is to use biomass to produce small quantities of a greater quantity of bio-based products and downstream, to use secondary waste, for the production of energy destined for internal or external use (Bell et al., 2014). Depending on the raw material or processing technology used, biorefineries can be classified into lignocellulosic, whole culture, green, marine, platform, conventional, chemical, and thermochemical (Cherubini et al., 2009). Another classification indicates that biorefineries can be a first and second generation or integrated (Trigo et al., 2012). In Table 2, information corresponding to each of them is shown.

Table 2 Classification of biorefineries
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For the efficient transformation of biomass, in addition to pretreatment activities, two conversion methods are used: biochemical and thermochemical. Biochemical processes are carried out by the action of microorganisms (fungi, bacteria, and yeasts), through biochemical reaction mechanisms; consider fermentation and anaerobic digestion, which produces biofuels and other chemicals, as well as biogas and biofertilizer. Thermochemical transformations are carried out at high temperatures and include combustion, gasification, and pyrolysis processes to produce thermal energy, synthesis gas, and bioproducts (bio-oil and bio-carbon). The conversion rate in these processes depends on the operating conditions: temperature, pressure, feed rate, heating time, biomass particle size, catalytic activity (Ferreira, 2017; Vaz, 2019).

Bioplastic production would be a value-added co-product within biorefining, as happens in oil refineries with the production of plastics and chemicals. The challenge, in this case, is to find biomass compatible with the biomaterial to be obtained in a biorefinery scenario where the markets justify its production (Snell & Peoples, 2009). The implementation of a biorefinery platform that uses food waste as raw material is an interesting option (Tsang et al., 2019). This concept is possible for the production of thermoplastic starches, as well as bacterial polymers. The selection of biomass, the processing methodologies, and the correct integration in products and co-products to be obtained, would contribute to a viable biorefinery from an economic and environmental point of view.

It is aimed at an integrated biorefinery, where all the flows generated in the process are used. Concerning agribusiness, waste from the starch industry (reject raw materials, shells, seeds) could be used to extract the remaining starch and use it in the manufacture of thermoplastic starch. A similar case would happen in the manufacture of juices and beverages, where it is possible to use the waste generated (seeds, peels, skins) to obtain the sugars present and use them as platform molecules or lowcost substrates in subsequent fermentation processes. A representation of what has been described is shown in Fig. 3.

Fig. 3
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Biorefining for the production of bioplastics

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Biorefining is a promising concept that seeks to close loops to value biomass in a circular economy framework and comprehensively address the economic, environmental, and social aspects of the industrial sector (Lindorfer et al., 2019). Although it represents a great challenge, adequate integration of technologies and raw materials will allow the establishment of future sustainable production chains for the production of different bioproducts, which are also competitive in the market and which lead to the progressive substitution of the products obtained by the industry oil company (Cherubini, 2010; Ubando et al., 2020).

5 The Future of Bioplastics

The use of environmentally friendly materials is a topic that has gained interest in recent years, both at an environmental and commercial level. The plastics industry immersed in this reality has shown some experiences in which petroleum derivatives are being replaced by others of renewable origin, to produce partially based plastics such as biopolyethylene terephthalate (bio-PET) or totally biodegradable such as polylactic acid. In other cases, it has been possible to obtain bioplastics from fossil resources, such as polycaprolactone.

Currently, bioplastics have a market share close to 1% of the total plastic produced in the world, with annual growth rates between 20 and 30% and this behavior is expected to continue for the next 5 years. Dadas las altas tasas de crecimiento en el uso de ácido poliláctico, polipropileno de base biológica y polihidroxialcanoatos, se estima que la producción de este material pase de 2,11 MMt en el año 2020 a 2,87 MMt para el año 2025 (European Bioplastics, 2020; Lackner, 2015).

But this represents a great challenge not only for the industry but for the community in general. Beyond the biomass transformation technologies and the operational requirements for the production processes to be profitable, aspects related to the environmental management of the waste generated must be taken into account, the establishment of clear legislation by the governments, as well as consumer trends by users.

On the environmental side, it must be taken into account that not all bioplastics are biodegradable. About half of the current bioplastics market is nonbiodegradable and their end-of-life disposal will be problematic if not properly addressed. The main nonbiodegradable bioplastics are biopolyethylene, biopolypropylene, biopolyethylene terephthalate, and biopolyamide. For biopolyethylene, biopolypropylene, given their chemical structure, they recommend using them as raw materials for catalytic pyrolysis and from them producing liquid hydrocarbons. Instead, for biopolyethylene and PLA, they suggest it as potential raw materials for the gasification process (Rahman & Boi, 2021). It should be remembered that bio-based materials or biodegradable materials such as PLA have great potential to be compostable (Sidek et al., 2019).

Knowledge about the biodegradability of bioplastics is a starting point for legislators to assess environmental impacts and create legislation to limit these impacts as much as possible. Within this context, worldwide guidelines should be developed for the production and use of bioplastics, as well as waste management (Polman et al., 2021; Sidek et al., 2019).

As far as users are concerned, communication is needed between societies and markets on how to put bioplastics into service in the future. It is necessary to promote sustainable consumer behavior and determine the factors that influence their behavior in terms of purchasing the purchases they make so that these revolve around sustainability (Thakur et al., 2018; Zwicker et al., 2020).

Finally, bioplastics represent an opportunity to tackle the problem caused by resource depletion and plastic pollution. Current obstacles and challenges must be overcome to reach the production goals foreseen for the coming years.

6 Conclusions

The use of agro-industrial waste for the production of bioplastic is an option that has gained interest in recent years, as a strategy for its recovery and to obtain an emerging material that is respectful with the environment. Although the current market for bioplastics is low when compared to the production of synthetic plastic, there are some experiences of biorefineries with favorable results for the production of bioplastics. Future trends indicate that the production of bioplastics will increase in the coming years, to progressively replace traditional plastics. For this reason and given the composition of agribusiness residues, they represent an attractive option for them to become their raw material, within a framework of circular economy and bioeconomy.