An Overview on Bioeconomy in Agricultural Sector, Biomass Production, Recycling Methods, and Circular Economy Considerations

Abstract

This review examines the essential components of a circular economy (CE) in relation to the agricultural sector. The bioeconomy and circular economy are crucial for sustainable global industrial growth, focusing on closed-loop systems. The sustainability debate centers on intergenerational equity and natural capital. The CE requires new environmental technologies and global coordination in order to combat climate change and biodiversity loss. In addition, efficient food production and waste reduction are essential due to population growth. However, biomass is vital for a bio-based economy, impacting food waste and climate change. Grasslands support sustainable dairy production and carbon sequestration. Thus, effective waste and wastewater management are critical, with biomass energy providing renewable alternatives. Nonetheless, biofuels remain key for sustainability, focusing on pollution control and Green Chemistry. It is well known that sustainable transportation relies on bioenergy, with ongoing research improving processes and discovering new fuels. One notable challenge is managing heavy metals in biofuel production, and this underscores the need for eco-friendly energy solutions. The main purpose for this review paper is to create a connection between circular economy aspects and the agricultural system, with focus on the following: bioeconomy research, biomass utilities, and biofuel production. Extensive research was performed on the specialized literature by putting in common the main problems. Key subjects in this paper include the use of biomass in agriculture, the problems of plastic recycling, and the function of the CE in mitigating climate change and biodiversity loss. Efficient food production and waste minimization are highlighted due to their relevance in a growing population. The study’s detailed research and discussion aim to give important insights into how these practices might promote economic development and sustainability. Furthermore, the study covers important waste management issues such as food waste, plant composting, and chemical waste neutralization. These topics are critical to understanding the circular economy’s broader implications for minimizing environmental damage and implementing sustainable waste management strategies.

1. Introduction

Recently, the term “bioeconomy” has become more and more popular. Many countries have approached this subject in different ways [1]. The bioeconomy is a notion that has sparked interest because of the many problems facing the global economy. These issues include the sustainable management of natural resources, improving public health, sustainable production, integrated economics, climate change mitigation, social growth, and sustainable global development [2].

The bioeconomy refers to a unique refining and value-creation chain in which products from the primary biomass production industry are moving to the processing industry and distribution and trade chains, reaching users as biomaterials and food for further refining, manufacturing products, and commercial products, resulting in a whole closed-circuit economic system. The aspects that have been presented, named biomass generation, production and processing, distribution, and consumption, are linked by knowledge, use system, and innovation creation [3].

The bioeconomy sector includes all operations linked to new product development, along with the transformation and reuse of natural resources [4,5,6,7]. As a result, it contains components of fisheries, agriculture, food, forestry, paper manufacturing, and cellulose production, along with the biotechnology, chemical, and energy industries [8]. The European Union and its member countries’ answer to global concerns, such as requiring sustainable management for biological resources, food security, and a decreasing reliance on nonrenewable fund, is represented by the concept named “bioeconomy”. Agriculture is an area that plays a key role in the development of the bioeconomy, as it is used to produce the raw material for most of the biomass used to manufacture bioproducts [9]. After the publication of the Brundtland Report in 1987 [10], the novelties of sustainable agriculture have gained importance, alongside the broader concept of sustainable development [10]. However, the term “sustainable agriculture”, like the theory of sustainable development, is ambiguous in how it is defined [11]. This trait has resulted in the formation of a wide range of various discussions and perspectives on sustainable agriculture [11,12,13,14,15,16,17,18], making the debate and implementation of this concept exceedingly complex. It also enables the concept to be exploited by those with entrenched interests that utilize it for their own goals [19].

In order to increase the efficiency of the use of limited resources, the reuse and recycling of residual materials from industrial systems is adopted. As producers move from linear to circular economies, they are stimulated and receive government assistance due to the constant development of the economy. This article is looking to provide an overview about biomass from the agriculture sector and draw connections to the circular economy. The study’s extensive analysis and discussion attempts to provide useful insights into how these practices might foster economic development and sustainability. In addition, the study will address significant waste management concerns in the same manner with food waste, vegetable composting, and chemical neutralization. These themes are critical for understanding the circular economy’s larger implications for environmental impact reduction and sustainable waste management techniques.

The aim for this review paper was to highlight the connection between circular economy aspects and the agricultural system, with a focus on bioeconomy research, biomass utilities, and biofuel production. The main research question was as follows: “How can the circular economy and bioeconomy be better integrated in the agricultural sector?”

The study objectives of this study are as follows:

• An overview on recent bioeconomy studies focusing on the published data from Google Scholar, Web of Science, and PubMed;
• To extensively discuss the utilities of biomass from the agricultural sector;
• To gather feasible methods of recycling in the agricultural sector;
• To discuss aspects regarding biofuel production.

By accomplishing these study objectives, a clear and interdisciplinary perspective about these theme was obtained.

2. Materials and Methods

In order to complete the objectives of this paper, firstly an extensive literature search was performed.

The study took place in May 2024. We used “Google Search” [20] as the search engine. Available information from scientific articles was found on recognized platforms such as Web of Science [21], PubMed [22], and Google Scholar [23]. In order to find and access relevant and up-to-date sources, specific keywords such as “bioeconomy”, “biofuel”, “circular economy”, “circular economy and agriculture”, “food waste”, “sustainability”, and “biomass” were utilized. The search was accomplished for different years, starting with the year 2000. A total number of 9584 scientific works were obtained. Secondly, a critical evaluation of the most relevant paper abstracts was accomplished. An extensive investigation was conducted, meaning reading and analysis of several papers (250), research articles, and reviews. Between these 250 articles, those which best fit and were most related to the theme were used for the discussion part of this paper. To complete this process, important viewpoints, trends, and results that were relevant to the research objectives were identified.

Also, logical diagrams were created, using a specific website, VOSviewer [24]. These were based on the data that were extracted. Additionally, VOSviewer has text mining tools that may be used to create and display co-occurrence networks of significant phrases that have been taken from a corpus of scientific literature. Although the idea behind these diagrams is simple, a deep understanding of the subject and an understanding of how all the terms, procedures, and key elements of the subject are organized was required. These charts were created to make complex information easier to understand and to make it easier for readers to understand.

These charts also serve as an educational tool, giving both experts and non-experts a deeper understanding of our research area. This network view makes it easier to comprehend the complex relationships that exist between various aspects of sustainability and the circular economy. It does this by showing the connections between ideas like food waste, block chain, recycling, and emerging technologies within the larger framework of building a sustainable future.

The goal was to close the knowledge gap between the visual representation of data and the actual application of intricate scientific concepts. In addition to aiding in the dissemination of information, this approach promotes more investigation and debate in the area. Our ultimate objective was to produce a tool for scholars, decision-makers, and everybody interested in the bioeconomy and sustainable energy solutions. With regard to the prospects and difficulties of biomass and biofuels in the framework of sustainable development generally, we hope that these initiatives will foster a more thorough and knowledgeable conversation.

The following provides a quick explanation for the implementation of these two approaches. The map containing the keywords is divided into three large components: the large and centralized nodes represent essential and frequently encountered terms, such as “circular economy” and “sustainability”. The terms connected to them indicate specific sub-themes and applicability such as “bioeconomy” and “recycling and reusability”, and the grouping of these terms in clusters suggests various sub-domains. One can also observe the links between these components, which suggest the frequency with which two terms appear together in the same documents ). The map including the crucial places for practical recycling procedures is organized into three big components: the large and centered nodes indicate vital and commonly used phrases, such as “plastics” and “recycling”. The terms associated with them imply particular sub-themes and application, such as “waste management” and “greenhouse gases”, and the clustering of these phrases reveals multiple sub-domains. One may also see the linkages between these components, which indicate the frequency with which two phrases appear together in the same papers.

Also, a table containing the main sources of biofuels, together with the principal chemical method of obtaining them, was created. This helps to overview the main sources.

3. Overview of Bioeconomics Research

In the context of the circular economy, articles on the bioeconomy, sustainability, agriculture, and recycling were collected from the Web of Science (WoS). Starting with 2000 and continuing until 2024, there are over 5000 research articles related to the bioeconomy, and research in this field has shown an upward trend since the year 2000. Such data were also collected from Google Scholar (GS), in the same period of years, but the number of publications is significantly higher (9584), but still with an upward trend (Figure 1).

In these papers, various aspects of these topics are discussed. For example, the circular economy is a model about remaking, environmental behavior, remanufacturing, the prioritization of loss in habitual systems, the conversion of materials and things, the prevention of food waste, pollution principles, and strategic incentive policies for all shareholders (supplier, manufacturer, and customer) [26,27]. However, the governments of only 55% of global greenhouse gas emitters have set specific targets for further reductions in carbon emissions by 2030. In addition, most nations are on track to achieve net zero carbon emissions by 2050–2070 [28,29].

Indeed, the economic industry, which includes the output of consumer and investment products, uses natural potential and generates a wide range of waste that can be utilized in the production process. Some of this waste, such as metal, paper, batteries, plastic, glass, electronics, and other waste, can be saved and remanufactured. To produce energy, organic residues can even be used as fertilizers or fuel. In China and Europe, it has become essential to pay attention to issues related to natural resources and the environment, as well as to develop policies that support the concept of the European Community. The understanding of the CE differs between the two countries, as pointed out by McDowall et al. [30]; China has a broader perspective on environmental issues such as pollution. Instead, European concerns focus on natural resources, business opportunities, and waste. According to China’s National Bureau of Statistics, the total amount of municipal solid garbage arrived at 191.4 million tons in 2015, so the awareness of the importance of the CE is not a surprise (2015).

Transformative change is required to implement sustainable methods of production and consumption in order to address social issues such the depletion of resources, global warming, and environmental degradation. A biomass-based economy, rather than one based on fossil fuels, signifies a dramatic change in agricultural, technological, and social systems. Alternatively referred to as a knowledge-based bioeconomy or a bio-based economy (KBBE), this is a financial system in which the basic building blocks for materials and renewable biological resources, such as plants and animals, are the source of chemicals and energy [31,32,33].

Waste can be supposed to be produced as the goods/materials move towards the end of their lifecycle in a linear economy [34]. The goals set by the US Plastics Pact and the European Union to achieve 50% recycling or composting of plastic packaging by 2025 require innovation in recycling [35].

There are numerous technologies used for recycling worldwide. Compared to ores and minerals, recycling can be an economic opportunity because the precious metal content of common waste electrical and electronic equipment (WEEE), fuel cells, batteries, catalytic converters for automobiles, or end-of-life industry and electrical equipment and electronics (WEEE) is much higher [36]. In addition, the battery industry uses active materials from used batteries to create new batteries by repurposing the cathode. This provides economic and environmental improvements [37].

The rebirth of critical materials is an essential component of sustainable development. However, the use of environmentally damaging processes seems somewhat counterintuitive when it comes to recovering precious metals that are scarce, for the purpose of “Urban Mining” [37,38]. There is a discussion of the challenges associated with metal additive manufacturing certification, followed by a consideration of the business case and environmental implications of this technology [39].

There are also technological innovation interests and recycled materials and collaborations among sustainable designers, textile manufacturers, and fashion retailers that have been studied [40].

Most governments and economies in recent years, including the United States and China, have argued that the circular economy is essential for industrial progress [41].

The area of forest plantations in most developed countries is increasing in response to increased wood consumption. However, deforestation in tropical areas of the world continues to be a significant problem [42]. To maximize yield, arborists often use intensive forest management. This results in wood with wide growth rings, less density, less heartwood, and usually less durability [43]. Many use environmentally toxic compounds, even though there are techniques for alteration or preservation that can improve the wood’s durability. While research for sustainable and effective methods is needed [44], the study of characteristics related to the natural durability of wood is essential for increasing the life of wood products, both when choosing a suitable wood species for use and in general. It is very possible that gelam wood could be used in Banjarmasin city and South Kalimantan province. Both in terms of cost and adaptability to swampy terrain, it has several advantages compared to precast concrete foundations. This is because group foundations have higher stiffness during lateral push and less reduction than single piles [45].

Biomass is one of the few practical ways to replace fossil feedstock with a renewable resource in the chemical, heavy road transportation, marine, and aviation industries, therefore reducing their greenhouse gas emissions [46,47,48,49,50].

Plastics are becoming an essential and unavoidable aspect of our everyday existence. The annual plastic use has been continuously increasing. The main reasons for its impressive growth are its low density, robustness, extended lifespan, simplicity of manufacturing, light weight, and inexpensive cost. Polymers have been utilized in a variety of purposes, including food distribution and preservation, housing, communications equipment, water desalination, land and soil conservation, artificial surgical procedures, medical delivery systems, automotive and industrial uses, and security systems. Because they may be used for so many different things, plastics add a growing quantity of solid trash [51].

Plastic recycling must be included in every handling of plastic garbage scheme. Besides decreasing trash disposal in landfills, it may considerably contribute to raw petrochemical product conservation and energy savings [52,53]. According to Rebeiz and Craft [53], a few technological and economic restrictions now obstruct the complete and efficient recycling of plastic trash into useful products.

The concept of sustainability is well-known as “weak” or “strong” in the international literature. Weak sustainability requires equity across generations—resources now must be accessible for future generations—as well as the ability to replace natural resources with artificially produced wealth or human capital, including labor qualities, skills, education, and capacity [54].

A serious sustainability concern in developed nations is the advancement of gratifying lifestyles that utilize fewer of the resources of the globe than is now the case. People seek quality of life once they have progressed above subsistence living by diversifying their food, shelter, leisure time, consumption, and lifestyles. In developed nations, common lifestyles are urban—rich and poor—with a shift to suburbs in the United States. Rural regions are frequently utilized for highly automated mass production of food, lumber, and other resources, which necessitates a minimal infrastructure [55].

Agriculture, the industry with the greatest amount of primary output, belongs to the various industries of the bioeconomy [56,57]. Agriculture influences cultural environments while also being connected with soil and water resource degradation, as well as declines in associated goods and ecological services. It is to blame for biological variety loss and 13.5% of global greenhouse gas emissions [58]. Some physiological indices can be applied to numerous plant species and can offer accurate information regarding their health [59,60]. Also, some organisms are known as bioindicators and have been chosen to be tested for various chemicals [61].

The circular economy encourages the transformation of a closed-production system using the linear utilization model, whereby trash is recycled from manufacturing and consumption and added to the market to produce fresh value [62]. It is therefore critical to reduce consumption and reuse materials in order to close the circular loop. Because their choices may promote or inhibit circularity, consumers play a crucial role in the circular economy [62,63]. The circular economy allows for multiple loops, like recycling, repair, refurbishing, and reuse. Recycling is not the most desirable loop in an economy that is circular, but it is an inevitable loop for many items and situations (such as a broken plastic box or plastic wrap included in packaging); therefore, it is worth looking in to. Products created from reused plastics, textiles, or metals include clothing, durables (like furniture, appliances, and vehicle components), and rapidly evolving consumer goods (FMCG) (such as kitchen bags, paper products, detergents, and garbage bags) [64,65,66,67,68]. Previous research has not taken a complete approach to the acceptability of items made using recycled materials since it has only examined the effects of certain influencing elements. Separate investigation of the influencing factors does not allow for the capture of every factor impacting the use of items manufactured from recycled resources. For instance, although consumers like and see items made of recycled materials as ecologically benign [65], they are often not preferred by customers [68].

The circular economy is regarded as a critical paradigm for industrial economics pursuing long-term growth [69,70,71,72,73]. At the moment, the key issue is how to transform the existing consumption pattern, which is based on a production–consumption–waste model, into a CE, which is regenerative by definition and is based on a production–consumption–reuse model. The CE is most commonly described as a mix of reduce, reuse, and recycle operations, according to Kirchherr et al. [74]. Thus, investing in novel environmental protection technology is critical in the circular economy [73].

The difficulty of doing research on the connection among the CE and the sustainable development idea, along with the many words associated with it, has been the subject of several assessments in recent times. For example, the term “CE” is used in certain pieces of research to describe a new ecological paradigm that promotes development through the use of CE techniques [74,75,76,77]. Several researchers have examined the drawbacks and restrictions of the CE in relation to global sustainability [78,79]. Moreover, the consistency of the CE has been the target of debates and critiques of different conceptualizations of the CE [74,79]. Other authors support business paradigms (based on entrepreneurial innovation) as a strong basis for the shift to the CE, such as De Pádua Pieroni et al. [80] (with sustainability as a strong foundation).

In Figure 2, representation of the key words about bioeconomy and their connections can be observed. The main themes are represented by “circular economy” and “sustainability”, and these are related to different concepts. The groups of related notions are represented by the following: recycling and reuse (connected to the circular economy, includes pre-construction concepts and ecological solutions); food waste and biorefinery (focuses on food waste, biorefinery, and related manufacturing processes such as additive manufacturing and thermoplastic materials); emerging technologies and supply chains (emerging technologies, plastics value chain, and circular supply chains); Blockchain and IoT (connected to both circular economy and sustainability); Bioeconomy and food (under the sustainability node, includes concepts such as bioeconomy, food, circularity and food packaging). Color-coded clusters can be explained by the appearance of different colors representing different groups or groups of related concepts. The size of the nodes and the thickness of the edges indicate the significance or strength of the connections.

The distinct colors used in this image represent different groupings or collections with similar ideas. The importance of the connections is shown by the thickness of the edges and the size of the nodes. With the help of visualizing this network, it is easier to understand the complex relationships that exist between different aspects of the sustainability of the circular economy. For building a sustainable future, it is important to visualize the connections between food waste, recycling, and emerging technologies.

4. Biomass from the Agricultural Sector

4.1. Food and Collected Waste

The most pressing scientific, economic, social, and ethical dilemma that humanity has today is preserving our planet Earth as the ideal home for future generations. Nonetheless, according to the planetary limits concept proposed by Rockström et al. [81], over a decade ago, mankind already passed the boundaries for a safe operating area in three of the nine major planetary systems, namely climate change, the nitrogen cycle, and biodiversity loss. It has become clear that, with a continually increasing global population, the roots of these global dangers are primarily human in nature. In reality, the population in the last 50 years has more than tripled [82] and such expansion can only be supported by establishing a productive worldwide food production system and, more seriously, by having no food waste. Food wastage is a major contributor to weather variation, accounting for a waste of around 1.3 billion tons of crops each year. This quantity is equivalent to 30% of all food production for human utilizations and 81% of world greenhouse gas emissions (GHG) connected with wasted food [83,84]. Food protein waste, being its most valued part, has a significant impact on the total issue. Intense animal protein production has a direct influence on climate change, accounting for 12% of all GHG emissions and 30% of all human-induced terrestrial biodiversity loss [85]. Plant protein synthesis, on the other hand, has severe and immediate ramifications for both the nitrogen and phosphorus cycles [86,87] and has an influence on the pace of biodiversity loss due to the conversion of pristine forest into agriculturally usable areas. Lastly, the biomass product-oriented value chain will be centered around bio-based products, including bio-based materials, bio-based substances, biofuels, and bioenergy, within the framework of a bio-based economy.

With an area of land of 2.9 million km² (90.4% of total geographic area) and a surface area of 3.2 million km², India is the sixth largest nation in the world. India’s entire land area is 60.5% agricultural land, or 1.79 million km². Agricultural land is defined as the portion of land that is exploitable (53.2% of total land area), under perpetual grassland (3.5% of total land area), and covered by perennial crops (3.8% of total land area) [88]. Using a net area under agricultural cultivation of over 180 million hectares with a cropping intensity of around 140% FAO of the United Nations, [89], Indian agriculture produces enormous amounts of biomass, a significant amount of which is made up of residues. According to Ravindranath et al. [90], Indian agriculture created at least 840 million tons of agricultural leftovers in 2010.

The globe generates 4 billion metric tons of food annually, which is sufficient to meet the needs of the estimated human population. However, over 1.3 billion tonnes of food is wasted before it is consumed [91].

According to Kim [92], evolved regions’ food losses in developed nations, such those in Europe, North America, and East Asia, totaled around USD 680 billion, whereas food losses in developing nations, like those in developed nations, were caused by inadequate technology and storage alternatives, subpar harvesting, transportation limitations, and unfavorable farming circumstances. Food waste is described as trash or by-products from hotels, canteens, households, restaurants, and the food industry. Surprisingly, food scraps are mostly caused by quality or quantitative degradation owing to food expiry, spoiling, spillage, or unintentional droppage [93]. The municipalities and households group has the greatest rate of food loss/waste, accounting for one-third of total food waste creation (around 39%). According to Koivupuro et al. [94], the following are the most prevalent causes of food waste: (i) overcooking; (ii) inadequate buying management; (iii) keeping food in less-than-ideal circumstances; (iv) misinterpreting the use-by and best-before dates; and (v) overstocking. The agricultural stage contributes the second-highest percentage of food waste (27%). Agricultural losses and waste are more common in low-income nations than in nations with a moderate to high income due to limitations in advanced infrastructure and technologies for harvesting [95]. North America follows Europe in terms of food waste creation by 1.3 billion tons, with 133 billion pounds of edible food wasted each year [96]. North America is the greatest producer of food waste, owing to inadequate cold-chain facilities, excess inventory, and market fluctuations, and a variety of consumer needs. Furthermore, Asia Pacific nations are predicted to develop steadily as food waste during transportation rises along with food being shipped to other nations. According to Otles et al. [97], unavailability of adequate technology, legislative structures and misunderstanding managerial actions and market signals, and ineffective waste management techniques all contribute to food waste losses.

Other than industrial and vehicle emissions, biomass burning is a substantial contributor to air pollution [98]. According to Akagi et al. [99], burning biomass is the second-largest producer of trace gases in the troposphere and the leading generator of main fine carbonaceous particles. According to Venkataraman et al. [100], around 18–30% of crop residue is burnt in agricultural areas. One of the key concerns in the field of sustainable development study has been resource efficiency. Strategic waste management is often viewed as essential for achieving high levels of resource efficiency [101,102]. Environmental conservation necessitates international collaboration as well as community engagement. This is why environmental conservation necessitates group efforts, and garbage recycling is no exception. Collective action, by definition, is the voluntary supply of public goods [103].

Grasslands represent 26% of the globe’s surface area, comprising the majority, and 69% of the land used for farming, which is the most economical method of feeding ruminants, including cattle kept for the production of milk or meat [104]. Grazed pastures promote dairy production sustainability in a variety of ways, including cheaper feeding costs [105], improved animal comfort and a decreased incidence of mastitis and lameness, a positive public perception, and improved milk quality [106]. Grasslands also play a significant part in the delivery of environmental and social services [107]. With proper management, a diversified variety of grass and legume species and types might enable the emergence of a broader range of microfauna and crop auxiliaries. Pastures have the potential to significantly reduce atmospheric CO₂ levels through soil carbon sequestration [108]. Grazing has been shown to influence the amount and movement of C in the plant layers above and below ground [109]. Herbivory has an influence on both above- and belowground biomass [110]. Comparisons of plots with and without grazing have been widely used to measure the impact of grazing on several aspects of ecological structure and function [111,112,113,114].

4.2. Reuse of Waste Water for Irrigation

Reusing wastewater is a crucial part of managing water demand since it helps to preserve clean, fresh water while reducing pollution to the environment and the total cost of supplies. Recent advances in technology and shifts in public opinion point to the possibilities for wastewater reuse in developing countries [115,116]. With population expansion, fast urbanization, and improved sanitation service coverage, the volume of collected and treated wastewater is projected to increase significantly [117,118,119,120]. Domestic, industrial, and commercial sources all create wastewater.

The household component is the greatest in many networks, accounting for up to 50–80% of total water usage [121,122]. The use of treated wastewater for irrigation can have both beneficial and detrimental effects on the environment [122], and the use of treated wastewater in agriculture may be beneficial to the environment with appropriate planning and management. However, with worldwide water shortages, both the primary and secondary uses of wastewater that is not treated in irrigation are increased by inadequate and inappropriate effluent treatment and disposal, as well as by growing fertilizer prices [123,124,125]. One of the current frequently utilized strategies is irrigation using wastewater that has been treated [126]. By utilizing part of the treated wastewater for industry and agriculture again, it relieves the demand on traditional water sources. The farming industry is the largest user of water—consuming roughly 92% of the water accessible in Iraq in 1992, up from 78% in 1980 because of substantial increases and growth of agricultural land—and the nutrients in this water can aid in developing plants rather than causing harm as in the case of river discharge [127]. The Earth has roughly 1351 million km³ of water [128], just 3% of which is suitable for drinking and agriculture [129]. In an ideal world, where all accessible water on Earth would be equitably allocated to a uniformly dispersed population, each individual would have access to 5000–6000 m³ of freshwater per year, according to an FAO report [130].

Oleaginous microorganisms, such as microalgae species, have been utilized in recent food scrap processing technology for biological purifying of wastewater because of their value, ease of use in bioreactor operations, ability to improve the environment, and efficacy in wastewater treatment [131]. During wastewater treatment, microalgae purify by-products such carbon sources, phosphorous, and nitrogen from food waste pollutants for development and growth [132]. Aerobic and anaerobic digestion are the two primary biological wastewater treatment methods; however, specific equipment is required, which raises the investment cost [133].

4.3. Energy Derived from Biomass

Using current technology such as gasifiers for entrained beds, fluidized beds, and fixed/moving beds to reduce food waste concerns by gasifying food scraps into purer syngas for power plant production rather than relying on fossil-based resources [134]. During the gasification process, natural agricultural refuse, including biomass and mixes of excess organic and inorganic materials, are transformed into syngas, also referred to as flammable gas. The process of gasification is thermochemical and produces gaseous combustible products like hydrogen, carbon monoxide (CO), methane (CH₄), and carbon dioxide (CO₂) gas from food waste by treating refractory degradable materials at temperatures that are higher than 800 degrees Celsius in an oxygen-limited environment [134].

Regenerative power production is seen as an urgent and necessary counter measure for resource and environmental sustainability. Bioenergy has garnered greater attention than other developing renewable energy sources like solar energy, geothermal energy, wind energy, hydropower, and marine energy [135]. Solar cell and wind turbine installations have increased rapidly in recent years [81]. However, CO₂ emissions continue to climb while atmospheric CO₂ concentrations surpass the safe global limits of 410 ppm [136]. This means that anthropogenic activity from fossil fuel burning continues to play a key part in energy consumption, despite significant attempts to generate electricity from solar and wind energy. Biofuels based on biomass have changed over the past few decades. First, they were made from food crops; then, they were made from lignocellulosic biomass; third, they were made from algal (macro- and microalgal) biomass; and, last, they were made from genetically modified microbial and algal systems [137,138,139]. Biomass may be directly burnt to provide warmth and force. However, a number of conversion methods have been developed to increase its value in industrial and other industries. These technologies are broadly classified as physical, chemical, biological, and thermochemical conversion processes [140].

5. Feasible Methods of Recycling in the Agricultural Sector

5.1. Composting Vegetable or Organic Waste and Recycling

Numerous types of waste, such those resulting from kitchen, foods, sewage, gardens and animals, but also municipal solid waste, are known as solid organic residues, if they contain an organic biodegradable fraction with a moisture content of less than 85–90% [141]. Municipal solid residue incineration emits noxious gases, polychlorinated dibenzo-p-dioxins, and dibenzofurans (PCDD/Fs), and open dumping, leads to emissions of greenhouse gases (e.g., CH_4, N₂O, and CO₂) and contributes to global warming and a decrease in air quality [142,143]. In developing nations, waste is mainly formed from biodegradable organic residues, being a principal source of GHG emissions caused by humans [144,145]. Overall, open garbage disposal degrades an area’s aesthetics by serving as a breeding zone for flies, different or pathogenic bacteria, as well as emitting bad aromas and leading to littered rubbish by stray animals. These types of conventional waste management techniques endanger the quality of ambient areas and human health, and contribute to losses in nutrients and different economic losses [146].

Composting is an ancient and low-cost process of converting waste from an organic source into beneficial compost. This can be utilized in different formulations in fertilizers or soil conditioners. Composting involves exothermic biodegradations, which involve a complex network of biochemical events, performed with the help of aerobic or facultative aerobic bacteria, which can catabolize the substrates necessary for metabolism and growth [147,148]. Since 1992, vegetable waste from different supermarkets located in the United States has been sent to organizations which deal with composting activities [149,150,151]. Not many researchers have studied supermarket waste, like vegetables and fruits. Others [152] have investigated the kinetics of thermophilic products resulting from pre-dried vegetable waste on a laboratory scale, using a temperature-controlled reactor. The process of composting includes the biological transformation of organic waste under regulated circumstances that allow biological activity to occur [153,154]. Composting is a versatile process that may be carried out in different systems, open or closed. Organic sources utilized in open systems are heaped in structures, rotated at known intervals in order to increase the medium aeration. Closed systems include reactors, which are more expensive, and which permit a greater control of the moisture and temperature [155].

The diminishing content of organic substances found in soils used for agriculture has become a concern globally. This contributes to soils with lower fertilities, and lower yields. Moreover, an impact on the physical features of soils can be observed, meaning changes in soil compactibility, mechanical strength, aggregation, and the capacity of water holding [156]. Recycling the biodegradable organic part of solid waste from crops can be an appropriate option to improve the soil quality, affected by the improper use of fertilizing substances or other compounds. Exploitation of agricultural organic residues provides opportunities for soil conditioning and for a proper continuous management of organic residues, and hence the limiting of ambient degradation caused by improper disposal (Figure 2) [156].

5.2. Recycling of Used Agricultural Equipment

For the protection of food security for countries, the technical potential of agro-industrial complexes must be efficient. An “Agricultural recycling” system, a resource-saving concept, should be implemented as quickly as possible as part of this [157,158,159,160]. Due to age and the necessity of replacing them with more sophisticated technological means, around 40–45% of the six million units which offer support for the agro-industrial complex should be totally decommissioned quickly. In recent years, some authors have mentioned that around 2–2.5 million units of this potential must be used, with no system which producing 65–70% of other resources [160]. Recently, their use has occurred without modern energy uses or the help of other resource-saving methods that are compatible with the surrounding habitat. It also has predominance of manual labor, together with a big decrease in material resources and the manufacturing of low-quality secondary resources.

The technical paradigm advocated by an “a-political” view of agro ecology suffers from similar shortcomings. If agro ecology is considered as the sum of science and practical appliance of principles to the administration or design of sustainable farms [161], this contributes to numerous conflicting narratives. Each of these has a purpose for creating healthier agricultural farms. Alternative agriculture techniques take numerous forms, including organic farming, biodynamic agriculture, permaculture, and natural farming. All of these strategies encourage different practices aimed at reducing reliance on synthetic chemical fertilizers, pesticides, and antibiotics, as well as leading to a reduction in production costs, which reduces the negative environmental effects of contemporary agricultural production [162].

5.3. Responsible Management of Chemical Waste

Green Chemistry (GC) represents the application of various chemical-related methods or procedures which can remove/limit the formation of products or any by-products hazardous for natural habitats and their inhabitants in order to satisfy the aims of Sustainable Chemistry [163,164]. For a long time, the end destinations for liquid and solid residue disposal in experimental fields that create chemical residues were in sinks and in general waste [165,166]. Because of waste diversity and high levels of accumulation, these activities pose significant dangers to both people and the environment [167,168,169]. In accordance with the legislation in the environmental domain and worldwide recommendations for them, the necessity to establish EE activities at all educational levels has raised, in accordance with research and regulations in this field [170]. This notion incorporates the Green Chemistry concept, used like tool at the molecular level, i.e., during the synthesis stage, but goes beyond this level by accounting “for not only the functionalities of a molecule that are necessary for its application, but also their impact and significance at the different stages of its life cycle” [170], which incorporates also a final step when the materials and product made thereof can be seen as residues.

Educational and scientific organizations are typically the source of chemistry-related residue production. These sorts of garbage require more consideration because their wide variety makes disposal problematic, as there is no “standard” treatment that can be used. Universities and faculties are seeking suitable ways to decrease the environmental hazards caused by waste created during practical laboratories or/and research operations in order to avoid environmental consequences [171,172,173].

In Figure 3, four central themes can be observed: plastic materials, recycling (which is closely related to another “plastic” node), sustainability, and environmental pollutants. The groups of concepts with which large themes are closely related are represented by the following: plastic materials and polymers (blue cluster); recycling and waste management (orange cluster); greenhouse gases and animals (red cluster); environmental pollutants (purple cluster); and sustainability (green cluster). Links are represented by thicker or thinner lines and nodes depending on the degree of interconnection between the previously presented themes.

6. Biofuel Production

Nowadays, bioenergy plays a massive role in enabling sustainable and continuous development strategies [174]. Of all sectors of the energy matrix, the transportation sector is the principal fossil fuel user, accounting for roughly 60% of the total oil demand [175]. Biofuels are liquid fuels produced by renewable sources. The most common biofuels utilized nowadays are bioethanol and biodiesel. Numerous initiatives to decarbonize the transportation industry have been established [176] and liquid biofuels have resulted as feasible options [177,178]. Green or habitat-friendly energy can be obtained from these sources of biomass, lessening the issues with the environment [179].

Research in the alternative fuel domain is an actual and quite important study area and has the capability to rising raise the performance of various engines, like those with internal combustion. Also, at the same time, the amount of generated pollution is clearly lower. The types of fuels from new and clean sources, which are suitable for diesel engines, are called biodiesel. Some sources have mentioned that biofuel production was approximatively 60 Million Tons of Oil Equivalent (Mtoe) in 2010 and was predicted to rise to almost 100 Mtoe in 2022 [175]. Numerous vegetal oils, such as waste cooking oil, rapeseed, olive, or Jatropha oils [180] are the source of it. This type of fuel has appeared on similar time frame to the diesel engine. Rudolf Diesel, over 120 years ago, ran an engine with peanut oil, for some hours, also anticipating an increase in the type of fuel, with it becoming comparable with diesel [30]. On the other hand, biofuels are biobutanol, bioethanol, and biogas. In diesel prototypes or engines, diesel can be blended with biodiesel or the last one can be used alone. So, one of the main benefits of biodiesel use is that this fuel can be utilized in diesel engines like diesel. No modifications in the geometry are required [181] and a reduction in habitat pollution can be observed [182].

The global emissions of carbon dioxide increased from approximatively 33 Billion Metric Tons (BMT) in 2010 to 38 BMT in the year 2022 [183].

The use of bioethanol can reduce the severity of the big global concern of greenhouse gas emission results [184]. The common fermentation processes used for obtaining ethanol are highly complex, also having the capacity to vary in time [185]. This compound can be produced from a wide range of natural materials, with a large content of carbohydrates. These can be hydrolyzed into glucids that can be fermented and then are converted into bioethanol [186]. The industrial process for the production of bioethanol has room for development. The simplest kind of modeling employed to potentially simulate a fermentation process is not sufficient.

Some of the potential sources, critical for bioethanol production with no big costs, are materials like lignocellulose, woodchips, grass, crop residues, sawdust, sludge, and livestock manure; the likelihood of employing these resources as the basis for production is frequently constrained by the very high cost of producing bioethanol using present machinery. The difficulties are often linked to the hydrolysis process’s high costs and lower yield. Research on the generation of bioethanol from lignocellulosic waste materials has examined various agricultural waste [186,187,188,189], municipal sludges [189], and municipal solid residues [190,191,192], forest products’ offal [193], leaf and yard wastes [194], but there are also some investigations that have been conducted on dairy and cattle manures [195,196,197,198].

Animal manures as well as the waste products from other agricultural practices have been incorporated in a variety of studies published in the literature pertaining to bioenergy and biofuels. In Mauritania, Africa, several writers [198] looked at the possibility of producing biogas from wastes derived from animal dung and slaughterhouses. The analysis found that whereas the northern portions of the nation have limited potential, the southern regions have significant promise. Silva Neto and Gallo [199] highlighted Brazil’s biogas potential from anaerobic vinasse decomposition. When evaluating the emissions of greenhouse gases avoided by producing energy from biogas, fossil fuel-based power plants were taken into account. The replacement of fossil fuel-based power plants by biogas power plants was calculated. The potential of China’s urban agricultural wastes as biogas was theoretically proved by Yan et al. [200], who also disclosed the rate at which these wastes are being used.

Biofuel production across the entire world increases annually (except in 2020) [201]. Central and South America are known for the production of nearly 27% of the total global biofuel production.

The United States of America produced approximately 6.5 billion liters, Indonesia 7.9 billion liters, Brazil 5.9 billion liters, Germany 3.8 billion liters, and other nations 16 billion liters of biodiesel in 2019 [202]. This fuel has a massive impact on different new sources which produce energy because of the creation of engines which are eco-friendly, with low carbon dioxide emissions, non-toxic, biodegradable, and with reduced costs [203]. Various sources of biological materials, such as different types of oils used in biofuel production, together with the principal method of obtaining them can be seen in

Table 1. Synthesis containing the natural sources from which biofuel can be obtained, together with the main obtaining method.

Used Material	Obtaining Method	Source
Sunflower oil	Transesterification	[204]
Hazelnut oil		[205]
Soybean oil		[206]
Palm oil		[207]
Neem oil		[208]
Algae		[209]
Jatropha curcus oil		[210]
Rubber seed oil		[211]
Waste cooking oil		[212]
Waste fish oil		[213]
Non-edible oil		[214]
Lignocellosic biomass	Enzymatic hydrolysis/ferment	[215]
Leaf and stem biomass	Anaerobic fermentation/Transesterification	[216]
Marine waste	Pyrolysis and gasification	[217]

.

The oil which results from cooking is known as a proper, probably the best commercial product, reutilized for biodiesel production [218]. Transesterification processes are suitable for the synthesis of biodiesel fuels [219].

Moreover, here straw, which is a residue from agriculture, can be discussed. It is utilized for biomass production, but it can be contaminated with various chemicals, including heavy metals. These seriously affect soil microbial communities and their abundance [220]. The presence of toxic chemicals slows down the degradation realized by microorganisms. Contaminated resources cannot be utilized in the field. Here, some new strategies for an optimization of processes after accumulation should be taken into consideration.

Regarding the advantages of using biofuels obtained from the residues which remain in agricultural processing, some of them can be mentioned. Probably the main advantage is the large quantity of plant biomass which can be used. Also, the fact that this biomass can be reused and can be found also from now on should be mentioned. This biomass supports development from the economical point of view, but also sustainably creates eco-friendly habitats producing energy and biochemicals [221].

Numerous efforts have been carried out for reducing the urban habitat problems which are related to the recycling, production, and disposal of polymer composites that are fiber-based. Also, there are numerous efforts to be carried out for their replacement. Pineapple fibers and compounds created with them appear to have the ability to create environmentally friendly products from plant residues [222].

Various studies have been conducted over time on individual fuels, like biogas or biodiesel. Less attention has been given to the blending of these renewable new fuels. It is a known fact that producer gas and biogas have bigger combustion features. These characteristics are bigger ignition energy and a greater laminar flame speed, resulting in a clean combustion [223]. So, the sum of hydrogen can be seen as a significant part in the determination of engine efficiency when a producer gas is used to fuel it; even the quick rate of flame propagation can be really tempered with nitrogen or carbon dioxide in producer gas. Biogas, made from carbon dioxide and methane, has a reduced laminar flame speed, a slower combustion rate, and a need for a bigger ignition energy when compared producer gas. Biogas, on the other hand, has a higher possibility of incomplete combustion in engines.

Last but not least, biofuels derived from microalgae and microbes are considered the third generation category [224]. The biomass from various algae which appear in wastewater treatment plants represent a rich source of proteins, carbohydrates, and lipids, but also secondary compounds. Of these, polyhydroxyalkanoates and carotenoids can be utilized as feedstock for microorganism fermentation processes. They are able to be recovered using electrochemical precipitation and flocculation methods. The algal biomass generated in wastewater treatment plants can be recovered by flocculation and electrochemical precipitation methods [221].

The main factor limiting potential biodiesel production in the U.S will be feedstock quantity. Some authors have mentioned that feedstock amount and crude oil price will be the factors that can reduce the production of biodiesel production, and this fuel sustainability will be interrupted by hydric stress in the future [222].

Features such as flow properties, high viscosity, reduced volatility, and reactivity of unsaturated hydrocarbon are clearly correlated with the composition of fatty acids and their structures [222]. Often, the process of converting a lipid to its lipid ester counterpart is employed to get around these issues. The fatty acid content of plant oils varies depending on the feedstock, resulting in differences in the length of the carbon chain and degree of unsaturation [223].

Biofuels can be liquid (e.g., bioethanol, biomethnol, biogasoline, biodiesel, and biobutanol), solid fuel, like biocoal, or gaseous (biogas, syngas, biomethane, and biohydrogen) [224]. The liquid fuels are utilized in principal for combustion engines from the transportation sectors. Gaseous and solid biofuels are necessary for power production or heating [225].

The use of various residues can enhance the concentration of biomolecules that are important for biofuel production, leading to a more economically viable large-scale process [225].

In relation to feedstock used to obtain biofuels, the most utilized are corn kernel fibers, woody biomass, municipal solid waste, and packed, high-crystalline structures, resistant to depolymerization and insoluble in water [226]. A well-branched polymer of xylose substituted with galactose, arabinose, and mannose, hemicellulose is the second carbohydrate component in corn fiber [227]. Some of the side chains can also contain acetyl groups of felurate [228].

Harvesting corn stover can be performed in the field wet or after drying. Shaping, raking, letting dry, windrowing, and packing the stover are all part of the dry harvest process. These are multi-pass steps that cannot be completed concurrently with grain harvesting. As a result, corn stover’s dry harvest is expensive. In contrast, the corn harvester can handle windrowing and shredding in a wet harvest as all necessary procedures may be completed on the entire day of corn harvesting. Lately, several researchers have concentrated on creating one-pass machines that can harvest grain and stover at the same time while leaving the necessary residue on the ground to act as fertilizer [229,230].

The leaf fibers found in pineapple (Ananas comosus) (PALFs) are known as residues to be used in biomass. These fibers are used in order to accomplish the synthesis of some valuable products. They also have the biggest productive system from the agro-industrial field. PALFs are not considered a very good source of biomass to be used in composting. On the other hand, these fibers have had good results in studies on applications in the automotive and construction sectors. In a review piece, data from publications that have been published about losses and the items that go along with them are examined, along with the disparity between the plan and its actual execution using a variety of approaches. Moreover, it has been argued that industrialization still has a lot of limits and that major practical efforts must be made. These are many things to think about and suggestions to follow can assist in getting over these issues. These include the development of fresh matrices, the creation of hybrid materials, and the configuration of fibers in composites. Furthermore, they are required to cultivate interest in high-value products at the level of industry [230].

7. Conclusions

The main scope of this paper was to discuss various aspect regarding the relation between the agricultural sector, bioeconomy, and CE, detailing notions related to biomass use, biofuel production, and composting. Recently, the number of investigations conducted on this joint domain has increased together with the growing interest in the reuse of numerous materials and products, and the necessity of finding new and suitable waste management ideas. In simple terms, the bioeconomy, which focuses on sustainable resource usage, connects with the CE to create efficient closed-loop systems. Governments across the world, particularly in China and the United States, emphasize the CE for industrial development. Agriculture’s involvement in biomass generation is consistent with sustainable development goals. Plastics, which are essential yet environmentally problematic, require appropriate recycling. The sustainability debate distinguishes between “weak” and “strong” sustainability, emphasizing intergenerational equality and natural capital substitutability. The circular economy is critical to long-term industrial growth, necessitating investments in novel environmental technology. However, disagreements over its coherence and multiple conceptualizations continue, with some calling for business models as the cornerstone for a sustainable transformation. In essence, global concerns necessitate coordinated efforts toward a more sustainable and circular future. Preserving the Earth for future generations is critical, yet humankind has gone beyond the acceptable limits in climate change, nitrogen cycles, and biodiversity loss. With the world’s population expanding, efficient food production and minimal food waste are important. Food waste contributes to climate change, which affects biodiversity and nutrient cycles. Biomass is critical to a bio-based economy.

Grasslands play an important role in sustainability by providing dairy production, environmental benefits, and carbon sequestration. Effective waste management and sustainable practices are critical to a healthy future. Wastewater reuse is critical for effective water management in the face of population increase and urbanization. Treated wastewater for irrigation helps to ease water scarcity, highlighting the importance of effective water usage. Food waste processing technology, which uses microorganisms such as microalgae, provides environmentally beneficial wastewater cleansing. Biomass energy, particularly gasification, provides a long-term solution to food waste while also contributing to renewable energy generation. Despite advances in solar and wind energy, biomass-based biofuels remain critical to resource and environmental sustainability.

Biomass conversion processes increase its worth in a variety of businesses, under-lining its versatile use as a renewable energy source. Solid organic wastes, such as sewage sludge and different agricultural, municipal, and industrial wastes, can cause environmental problems such as air pollution and greenhouse gas emissions if not adequately managed. Composting is a low-cost method for converting organic waste into useful compost, which acts as a soil conditioner and organic fertilizer. Recycling the biodegradable organic component of solid waste in agriculture improves soil quality while reducing environmental deterioration. Responsible chemical waste management, governed by Green Chemistry principles, seeks to eliminate harmful by-products while promoting sustainability in educational and scientific institutions. Bioenergy, including biodiesel and bioethanol, is critical for sustainable development, particularly in transportation. Biodiesel, made from a variety of oilseeds, is a greener alternative to diesel engines. Ongoing research aims to improve bioethanol production from lignocellulosic materials, whereas agricultural waste-based biofuels, such as animal manure, have been acknowledged for their sustainability. The research also investigates renewable fuels such as biogas and producer gas. The challenges include dealing with heavy metals from biofuel manufacturing and ensuring safe disposal. The focus is on research and practical implementation of eco-friendly energy solutions.

In this context, some recommendations for stakeholders can be provided. For policymakers, it is important to create and develop new programs for stimulating innovation in the field of recycling in the agricultural sector. Also, the dissemination of suitable waste management techniques, including those in relation to biomass derived from agriculture, should be carried out using various methods of communication.

Practitioners from agricultural sectors should pay more attention to residues resulting from their crops.

Nonetheless, researchers and academic staff involved in agricultural studies should conduct inter- and transdisciplinary investigations, in order to obtain various data that can be used for improving biofuel quality, recycling, and proper waste management processes or discovering new utilities of the residual biomass from crops.

Limitations of this type of investigation are related to the necessity of collaboration between researchers, people from industry, practitioners, and policymakers for making large studies. Starting with this limitation, studies on new utilities of biomass and agricultural residues are harder to accomplish. Firstly, these limitation may result from obtaining data, because they may be incomplete or inaccurate and/or even non-existent for certain study areas. These limitations can affect the complexity, as well as the validity, of the studies.

Secondly, another encountered limitation is the transfer of technology to communities and industries, this being due to existing barriers related to costs and local adaptation. Also, the technology needed is not always available for these interdisciplinary studies. Better communication between these stakeholders will promote the development of new strategies and methods.

Another limitation is related to the poor communication regarding the implantation of the CE and reuse and recycling strategies between farms in some countries. Common policies and workshops could be useful for facilitating communication between practitioners.

The level of knowledge and awareness on issues related to sustainability can vary, influencing the adoption of sustainable practices. The research and application of sustainability principles can be negatively influenced by global events such as economic crises or other policy problems.

Studies regarding the relation between crop management and proper uses of residual biomass are needed. Also, developing new methods, for faster and cheaper biomass processing and biofuel production could be useful.