Reduction and Reuse of Forestry and Agricultural Bio-Waste through Innovative Green Utilization Approaches: A Review

Abstract

Biomass waste, which is biodegradable and vastly underutilized, is generated in huge quantities worldwide. Forestry and agricultural biomass wastes are notable for their wide availability, high yield, biodegradability, and recyclability. The accumulation of these wastes not only occupies valuable land but causes serious environmental pollution, which can ultimately harm human health. Therefore, leveraging scientific technology to convert forestry and agricultural bio-waste into bioenergy and other valuable products is crucial. In this paper, common forestry and agricultural bio-waste such as straw, rice husks, livestock manure, tree branches, sawdust, and bioenergy (bioethanol, biogas, biodiesel, biohydrogen) were selected as keywords, with the theme of green and efficient utilization. This paper provides a comprehensive review of the sources of biomass waste, existing recycling technologies, and the potential of forestry and agricultural bio-waste as material additives and for conversion to biomass energy and other derivatives, along with future recycling prospects.

1. Introduction

In recent years, the rapid development of modern forestry, agriculture, and animal husbandry, along with the promotion of new urbanization, has led to a significant increase in the production of various biomass wastes, especially in developing countries. These wastes are abundant, diverse, and widely distributed [1]. Over 100 million tons of forestry and agricultural biomass waste are generated annually [2]. Moreover, these wastes are also regional, seasonal, and underutilized; some are discarded or discharged into the environment, resulting in wasted resources and environmental pollution [3]. The treatment and utilization of biomass waste are important for resource reuse and ecological safety [4]. Developed countries have established a relatively mature system for biomass waste utilization. Research covers various aspects, including the impact of biomass energy on food, land, energy, economy, and environment, as well as the improvement in utilization efficiency through empirical analysis. One of the greatest environmental challenges today is finding innovative ways to utilize waste and residues from industrial or agricultural processes [5]. More than 2 billion tons of municipal and agricultural waste are generated globally each year, of which biomass waste accounts for about 11% [6].

Landfilling has remained the primary means of waste treatment, but concerns persist regarding odor, land availability, residue run-off, and emissions of greenhouse gases, such as methane [7]. Meanwhile, biofuel production, utilizing raw materials, composting, and anaerobic digestion efficiently reduces biomass waste [8]. In developing countries, current bio-waste treatment methods include mainly landfill, incineration, and biochemical treatment [9]. Both landfill and incineration technologies do not fully harness the biomass energy in bio-waste, resulting in a waste of resources and energy [10]. Many countries have conducted in-depth research and industrialization efforts on the reuse of bio-waste. Biomass waste is mainly used as feed [11], fertilizer [12], industrial raw materials [13], biogas [14,15], fuels [16], etc. The recycling economy of utilizing bio-waste resources has been successfully implemented. In 1975, Brazil pioneered the large-scale production of fuel alcohol from bagasse [17]. Brazilian sugarcane ethanol reduced total greenhouse gas emissions, including direct and indirect land-use change emissions, by 61% during a life-cycle assessment.

Brazil has successfully replaced more than 26% of gasoline with sugarcane ethanol, making it the only country that does not exclusively offer pure gasoline [18]. Denmark has a remarkable technology for directly burning crop straw and forestry and agricultural waste [18]. The German recycling policy came into force in 1976. In 1976, the United States enacted the Resource Conservation and Recovery Act. The United States, Japan, Canada, Britain, Denmark, Italy, Germany, and other developed and developing countries such as the Philippines and Indonesia have formulated effective management measures for bio-waste recycling [17,19,20,21,22,23,24,25,26,27,28,29,30]. The Danish government has devised a waste plan since 1992 to manage agricultural waste effectively. Since 1997, all combustible waste material must be recycled for use as energy. In 2002, 81% of Denmark’s energy consumption came from biomass. Sweden’s forest area is broad, with a forest coverage rate of 60%. The utilization of forestry wastes such as bark, branches, and wood chips for energy crops and solid fuels has reached maturity. This encompasses the entire process from planting and harvesting raw materials to grain production, forming a comprehensive system of applications and services [11,12,13,14,15,16,17].

Biowastes produced by forestry and agricultural units are major reasons for worry by environmentalists, forestry, and agricultural departments. Because of the limitations and harmful impacts of conventional strategies, there is a need to develop sustainable technologies for the treatment of waste. Maximizing the utilization of biomass waste resources has emerged as a prominent topic in the current scientific research. The integration of waste treatment technologies based on the biorefinery concept has been employed globally, which can be exploited at a large scale to recover value-added products such as energy-rich chemicals, biopolymers, biofuels (biohydrogen), biogas, bioactive compounds, chemical building blocks, and materials from wastes. This article provides a brief introduction to the sources and existing recycling technologies of biomass waste and summarizes the current research status of forestry and agricultural biomass wastes in fields such as wood composite materials, bioenergy, polymer composites, etc. It also provides a prospective analysis of the application potential of recycling technology for forestry and agricultural biomass waste.

2. Overview of the Source and Utilization of Bio-Waste

The sources of bio-waste are large in quantity and variety, and there are five main types of bio-waste suitable for utilization including the following: (1) agriculture waste, including wheat straw, corn straw, sorghum straw, soybean straw, cotton straw, and wheat and rice husks produced in the processing of agricultural products; (2) feces and bedding grass produced by livestock and poultry breeding; (3) forestry waste, including branches, leaves, wood chips, forestry byproducts in forest tending and thinning operations, and sawdust, sawdust, branches, and other scraps produced in wood processing; (4) industrial organic waste, such as domestic sewage of urban residents and industrial organic waste generated by alcohol, sugar, food, pharmaceutical, papermaking, and slaughtering industries; and (5) solid bio-wastes in garbage, such as kitchen waste, household garbage, commercial garbage, and service garbage. The main sources of bio-waste are shown in Figure 1.

Bio-waste contains large amounts of lignin, cellulose, hemicellulose, and other organic substances [31]. Recycling and reusing biowaste in the supply and production chain will become an inevitable trend for societal development and tackling environmental problems. Using bio-waste for energy offers an effective solution to balance energy demands with environmental sustainability. Owing to the rapid depletion of non-renewable resources and increasing environmental pollution, there is a growing imperative to focus on utilizing biological resources, leading to ongoing advancements and improvements in various utilization technologies [32]. Direct combustion of bio-waste to obtain energy is the most common biomass energy utilization method, but improving utilization efficiency is still one of the current technology development issues [33]. The production of energy from bio-waste through microbial reactions could complement renewable energy sources by serving as eco-friendly sources of alternative energy [34]. Some developed countries have progressed from traditional landfilling and direct burning of green waste to adopting resource treatment methods. They reuse bio-waste resources through practices like organic coverings, bio-composting, biomass energy, edible fungi cultivation, wood–plastic processing, and the development and utilization of some biological products. Figure 2 illustrates the green, efficient, and sustainable utilization of bio-waste.

With the development of agricultural technology, the output of straw waste has greatly increased. Hence, using straw waste as biomass energy becomes an important direction for agricultural development [35]. Combined with the development of circular agriculture, the comprehensive treatment and utilization technology of human and poultry manure, crop straw, and household garbage is promoted to realize the circular utilization of resources and control the non-point source pollution of agriculture from the source [36]. Agricultural waste refers to biomass waste generated by agricultural production, the processing of agricultural products, and waste discharged from rural residents [37]. The utilization and development of agricultural waste are the basis for the industrial development of the agricultural recycling economy [38]. It can convert sugars and starchy carbohydrates into clean hydrogen energy, and this technique can also be applied using cheap cellulose and hemicellulose biomass wastes such as seaweed, seagrass, and crop straw as raw materials for hydrogen production.

Green plants have played a significant role in improving the urban environment and mitigating heat island effects because of their ecological functions, such as purifying air, carbon fixation and oxygen release, heat absorption and humidification, water conservation, biodiversity conservation, and landscape function [39]. With the continuous advancement of ecological construction and urban greening, green bio-waste has increased dramatically. The following two types of green bio-waste are generated: (1) garden plants, such as fallen leaves, withered flowers, and dead trees, and (2) artificially trimmed plant residues, such as grass clippings, shrub pruning, etc.

Agricultural residues refer to crops, agricultural byproducts, and secondary, organic, and agricultural waste. After proper treatment, they can be used as a substrate for agricultural cultivation, similar to corn stover, peanut shell, bagasse, cassava residue, and chicken manure. There are several ways to use bio-waste as an industrial material. It can be used as a material for cutting, bonding, assembly, and other mechanical processing technology and also for processing to make building and construction materials, such as composite materials, filling materials, cellulose fiber, materials for plane components, regenerated fibers, and so on. Maize straws, corn cobs, rice bran, corn starch residue, and bagasse can be processed by hydrolysis to produce sugar, furfural, oxalic acid, lignin materials or cellulose series polymers, and other industrial raw materials.

The large increase in the production of modern edible fungi and its large demand by society provides a route for applying forestry bio-waste in cultivating edible fungi [40]. Forestry bio-waste has a high content of organic matter [41]. Thus, it is generally suitable for use in edible fungus production bases after pulverization and sterilization, producing edible fungi sticks. The crushed bio-waste can account for 75%–85% of edible fungi cultivation materials. Bacteria is a common method for producing edible mushrooms such as oysters, shiitake, enoki, and black fungus. The remaining waste rods are used as raw materials for composting to produce organic fertilizer, which is returned to the forest lands or gardens to enrich the soil, establishing a sustainable cycle. Pretreatment and composting technologies for agricultural organic waste play a crucial role in promoting sustainable agricultural development.

3. Application of Bio-Waste in Composite Materials

In countries with low forest coverage, there are insufficient wood resources to supply raw materials for the wood and paper industries. Using agricultural wastes as raw materials for papermaking and composites can alleviate this issue. Plant fibers from bio-waste can be used to produce artificial fiberboard, cardboard, lightweight building materials [42], and other architectural decoration and packaging composite materials. These materials can include gypsum as a base material; fibrous waste as a reinforcing material for sound absorption, heat insulation, and ventilation; and rice husk as raw material for producing white carbon black, silicon carbide ceramics, and silicon nitride ceramics. Additionally, plant fiber waste such as straw and bagasse can be pulverized and used as raw material [43]. Bio-waste can also be used to reinforce polymers, matrix composites [44,45,46,47], and concrete materials. Forestry and agricultural bio-waste can also improve the performance of these composite materials (Table 1).

Table 1. Forestry and agricultural bio-waste reused in composite materials.

Raw Material	Composites Type	Tensile Strength (GPa)	Thickness Swelling (%)	MOR (MPa)	MOE (MPa)	IB (MPa)	Density (g/cm3)	Ref.
Sugarcane bagasse	PB	——	8.04	16	1879	0.35	0.6	[48]
Husks	PB	——	——	17.68	——	0.4	0.65	[49]
Macadamia nuts	PB	——	——	10.46	1441.74	0.83	0.55	[50]
Sunflower bark	PB	——	35	8.1	659	0.18	——	[51]
Flax board	PB	——	——	11.7	1040	0.32	——	[51]
Sunflower stalk	PB	——	——	10.2	1600	0.5	0.6	[48]
Miscanthus stalks	PB	——	30	18.0	1600~2500	0.28	0.63	[52]
Wood	NFPC	10–70	——	——	——	——	1.4	[53]
Cotton	NFPC	28–70	——	——	——	——	1.5	[54,55]
Bamboo	NFPC	11–17	——	——	——	——	0.6–1.1	[56,57]
NFPC	NFPC	53	——	——	——	——	1.4–1.5	[58]
Jute	NFPC	20–55	——	——	——	——	1.3–1.5	[56,59]

Note: MOR: modulus of rupture; MOE: modulus of elasticity; NFPC: nature fiber polymer composite; PB: particleboard.

Table 1. Forestry and agricultural bio-waste reused in composite materials.

Raw Material	Composites Type	Tensile Strength (GPa)	Thickness Swelling (%)	MOR (MPa)	MOE (MPa)	IB (MPa)	Density (g/cm3)	Ref.
Sugarcane bagasse	PB	——	8.04	16	1879	0.35	0.6	[48]
Husks	PB	——	——	17.68	——	0.4	0.65	[49]
Macadamia nuts	PB	——	——	10.46	1441.74	0.83	0.55	[50]
Sunflower bark	PB	——	35	8.1	659	0.18	——	[51]
Flax board	PB	——	——	11.7	1040	0.32	——	[51]
Sunflower stalk	PB	——	——	10.2	1600	0.5	0.6	[48]
Miscanthus stalks	PB	——	30	18.0	1600~2500	0.28	0.63	[52]
Wood	NFPC	10–70	——	——	——	——	1.4	[53]
Cotton	NFPC	28–70	——	——	——	——	1.5	[54,55]
Bamboo	NFPC	11–17	——	——	——	——	0.6–1.1	[56,57]
NFPC	NFPC	53	——	——	——	——	1.4–1.5	[58]
Jute	NFPC	20–55	——	——	——	——	1.3–1.5	[56,59]

Note: MOR: modulus of rupture; MOE: modulus of elasticity; NFPC: nature fiber polymer composite; PB: particleboard.

Much research has been performed on composite production using agricultural wastes such as rice straw, sunflower stalks, oil palms, opium poppy husks, soybean straw, wheat straw, cotton stalks, and canola straw (Table 1 and Figure 3). Bio-waste would play an important role in the future of the wood industry [60]. A polymeric cation exchange resin that absorbs heavy metals, such as cotton stalk skin, cotton boll shell, or the like, contains a phenolic hydroxyl chemical composition. Extracted polysaccharides from agricultural wastes can be used as coating preservatives for fruits and vegetables, edible packaging materials, industrial flocculants, lubricants, and moisturizers [1]. Yousefi et al. [61] studied the properties of medium-density fiberboard (MDF) made from agricultural residues, specifically canola straw. Their results showed that the properties of MDF made from canola straw were close to the minimum standard requirements for MDF. The dimensional stability of the MDFs improved as the adhesive content increased. The internal bond strength was positively affected by the increase in press time. Using agricultural residuals to create fiberboard is particularly notable in regions where sources of woody biomass are scarce or cost-prohibitive to obtain and manufacture into fiberboard. Much research was carried out to provide alternatives to woody biomass and ensure that multiple biomass sources could be used for MDF production. Sitz et al. [62] used soybean straw and wheat straw blended mediums to make densified fiberboards. Their results showed that pressure was the greatest factor in determining the board’s mechanical properties. Li et al. [63] evaluated the mechanical and physical properties of particleboard made from rice straw. Their results showed that the particle size of rice straw greatly affected the performance of straw particleboards. Compared with urea–formaldehyde resin-bonded panels, rice straw particleboards bonded with polymeric diphenylmethane diisocyanate resin exhibited much better performance. Kurokochi et al. [64,65] successfully prepared a binderless board from rice straw. As the contents of ash and silica decreased, the internal bonding tended to increase. The morphology of rice straw affected the performance of the board. Trichomes and wart-like bumps in the epidermis of rice straw could inhibit the bonding between particles. In addition, their study also indicated that the extraction of hexane and fine grinding were effective in increasing the self-bonding of binderless boards. Pirayesh et al. [66] used almond shells as a bio-waste resource to prepare a wood-based composite. Some chemical properties of the almond shells and the mechanical and physical properties of the composite were determined. Their results showed that adding almond shell particles reduced the composites’ flexural properties and internal bond strength. The water resistance was greatly improved with the increased content of almond shell particles. They concluded that almond shells can be used as a mixture of wood particles in the production of particleboard. In addition, they also investigated using walnut shells as raw materials for manufacturing composites. These results were similar to those of the almond shell particleboard [67]. Adding adhesive and hot pressing pressure significantly impacts the mechanical and physical properties of particle boards prepared from poppy shells [68] and tomato straw [69].

Bio-waste can also be used to reinforce polymers and matrix composites (Table 1 and Figure 3), such as the processing and characterization of epoxy matrix composites reinforced with short flakes. The properties of these composites have a low amount of porosity and improved micro-hardness [70]. One study used wheat straw, cornstalk, and corncob to prepare high-density polyethylene (HDPE) composites with a high content of agro-residues (65 wt%). The result showed the feasibility of utilizing agro-residues such as wheat straw, cornstalk, and corncob as alternative fillers for wood flour in thermoplastics. The mechanical properties of composites with wheat straw as filler showed better mechanical properties than cornstalk and corncob [71]. Sunflower stalk, corn stalk, and bagasse fibers were also used as alternatives to wood fibers in reinforced thermoplastic materials. Because of the strong interfacial bond between the fibers and the matrix polymer, the mechanical properties of the composites treated with the two coupling agents were significantly better than the untreated composites [72]. In another study, a series of characterization techniques were applied to determine the effects of biochar particles on the chemical and thermal composition of a composite. It was observed that adding biochar increased the presence of free radicals in the composite and improved the thermal conductivity. The experimental results showed that the chemical and thermal modification of biochar-added composites would effectively optimize the performance of the composite [73].

The cost of agricultural biomass is estimated to be 50% less than that of wood chips for particleboard and fiberboard production. As a result, replacing wood chips with alternative, non-wood raw materials could result in significant cost savings. Common agricultural waste used in particleboard production includes straws, shells, husks, stalks, leaves, and stems. For instance, particleboard made from walnut and almond shells exhibits lower thickness swelling and water absorption compared with wood-based particleboard. Bagasse is another excellent material for particleboard products, offering good physical and mechanical performance.

4. Utilization of Bio-Waste in Bioenergy

Biomass energy sources, such as biofuels, are readily available. It is the fourth largest available energy resource in the world [65,74,75]. Researchers continue to focus on the study of biofuel production from biomass, as it can be an efficient alternative to replace fossil fuels (Table 2 and Figure 4) [76]. Biofuel refers to liquid or gaseous fuels produced from biomass that are used in the transportation sector. They mainly include bioethanol, biodiesel, bio-dimethyl ether, synthetic hydrocarbons, hydrogen fuel, and biogas. The biofuel yield from Brazilian sugarcane is reported to reach 800 gallons per year [18]. Biofuels can enhance a country’s energy and economic security when prices are competitive with traditional fossil fuels. It was revealed in the recent literature that biomass wastes, especially those originally present in loose, fine, and amorphous forms, can be compressed into various molding fuels such as rods, particles, and blocks using compression molding technology [77]. This increase in the density of molding fuel can lead to improved combustion characteristics.

Figure 4. Classification of forestry and agricultural bio-waste available to produce bioenergy [78].

Figure 4. Classification of forestry and agricultural bio-waste available to produce bioenergy [78].

Table 2. Comparison of forestry and agricultural bio-waste reused to produce bioenergy products.

For bioethanol
Biomass type	Catalyst	Time	Temperature (℃)	Yield	Ref.
Sugarcane straw	lyophilized S. cerevisiae Y-904 yeast	33 h	40	70.63%	[79]
Molasses and paddystraw	Saccharomyces cerevisiae NGY10	12 h	40	83.59%	[80]
Poplar wood	AlCl3	72 h	200	59.76 g/L	[81]
Rice straw	yeast strain S. cerevisiae DBTIOCS24	72 h	42	0.42 g/g	[82]
For biodiesel
Guava seeds	ethyl propionate	——	40	24%	[83]
Spent coffee grounds	ethyl propionate	——	40	16.4%	[84]
Palm oil soap stock	methanol	——	40	91.68%	[84]
Spent coffee grounds	methanol	——	90	91.75%	[85]
For biogas
Barley Straw	——	30 d	80	340 mL/g	[86]
Sorghum straw	——	30 min	135	1419 mL/g	[87]
Rice straw	——	35 d	——	339 mL/g	[88]
For hydrogen
Rice straw	——	12 h	121	0.90 mol	[89]
Wheat straw	——	350 h	——	0.24 mol	[90]
Pine trees	——	——	80–90	0.99 mol	[91]
Olive trees	——	78 min	——	0.91 mol	[92]

Table 2. Comparison of forestry and agricultural bio-waste reused to produce bioenergy products.

For bioethanol
Biomass type	Catalyst	Time	Temperature (℃)	Yield	Ref.
Sugarcane straw	lyophilized S. cerevisiae Y-904 yeast	33 h	40	70.63%	[79]
Molasses and paddystraw	Saccharomyces cerevisiae NGY10	12 h	40	83.59%	[80]
Poplar wood	AlCl3	72 h	200	59.76 g/L	[81]
Rice straw	yeast strain S. cerevisiae DBTIOCS24	72 h	42	0.42 g/g	[82]
For biodiesel
Guava seeds	ethyl propionate	——	40	24%	[83]
Spent coffee grounds	ethyl propionate	——	40	16.4%	[84]
Palm oil soap stock	methanol	——	40	91.68%	[84]
Spent coffee grounds	methanol	——	90	91.75%	[85]
For biogas
Barley Straw	——	30 d	80	340 mL/g	[86]
Sorghum straw	——	30 min	135	1419 mL/g	[87]
Rice straw	——	35 d	——	339 mL/g	[88]
For hydrogen
Rice straw	——	12 h	121	0.90 mol	[89]
Wheat straw	——	350 h	——	0.24 mol	[90]
Pine trees	——	——	80–90	0.99 mol	[91]
Olive trees	——	78 min	——	0.91 mol	[92]

4.1. Biodiesel

Biodiesel production using forestry and agricultural bio-waste has garnered significant attention for its potential to address environmental and energy security concerns. This approach serves as a sustainable and environmentally friendly solution, effectively mitigating the ecological impact of waste disposal while reducing dependence on fossil fuels [93]. Selecting the right feedstock for biodiesel production is paramount, with a strong emphasis on harnessing the potential of underutilized bio-waste materials. The conversion of bio-waste to biodiesel minimizes the environmental footprint and enhances resource efficiency, effectively repurposing materials that might otherwise go to waste [94]. Various biochemical and thermochemical conversion methods have been explored to transform these bio-waste materials into biodiesel precursors, ensuring adaptability and flexibility to accommodate the diversity of bio-waste resources. Additionally, integrated bio-refineries hold great promise for bolstering economic viability and overall sustainability, allowing for the simultaneous production of biodiesel and other valuable bio-based products.

While using forestry and agricultural bio-waste for biodiesel production offers significant advantages, several challenges and considerations must be addressed to maximize its potential. One key challenge is the variability in feedstocks, which depends on factors such as geography, climate, and crop choice. This variability necessitates process optimization and customization for different feedstock sources. Additionally, feedstock availability, technology costs, and market demand influence the economic viability of biodiesel production from bio-waste [95]. Overcoming these challenges requires concerted research and development efforts to develop more efficient conversion technologies and to establish supportive policies and incentives. The ongoing pursuit of innovative green utilization approaches for bio-waste, coupled with a commitment to addressing these challenges, can reshape the landscape of biofuels and contribute to a more sustainable and environmentally responsible energy future.

Biodiesel is considered one of the best alternatives to fossil diesel because of its superior properties, such as lower toxicity, biodegradability, renewability, and reduced harmful tailpipe combustion emissions [96]. The electrolysis method has recently been reported as a potential method to produce biodiesel from biomass waste. Biodiesel is mainly a monoalkyl ester composed of vegetable oil, animal fat, or other materials mainly composed of triacylglycerol. Forestry and agricultural biomass waste have great potential for producing green diesel fuel [97]. Electrolysis is a promising method for producing biodiesel from biomass waste. Several studies have explored this method for converting waste cooking oil and other feedstocks into biodiesel. The process involves using an electrolysis cell with specific conditions, including catalyst concentration, the alcohol/oil ratio, voltage, and the presence of water. The resulting biodiesel yield was influenced by factors such as the amount of co-solvent added, water content, methanol/oil ratio, electrolysis voltage, and NaCl concentration. Additionally, the transesterification of waste anchovy fish oils has been investigated, and the resulting biodiesel was found to contain a significant proportion of saturated fatty acids, thus improving cetane number and reducing NOx emissions when used as a fuel in engines. These findings underscore the potential of electrolysis as a viable method for biodiesel production and highlight the importance of optimizing various parameters to achieve desirable biodiesel yields and properties [98].

Moreover, the content of value-added nitrogen compounds is notably high, offering a promising avenue for future industrial development. The copious consumption of coffee daily has led to the widespread availability of coffee grounds. These grounds contain approximately 15–86 wt% oil and have great potential for biodiesel production. After continuous purification, one study found that the resulting biodiesel exhibited good quality, with glycerol and glycerol ester contents falling below the EN 14214 limits [99]. Muanruksa et al. [84] introduced a novel approach that involves the enzymatic esterification of soap raw materials for biodiesel production. Utilizing low-cost palm oil soap raw material waste, the recovery rate of biodiesel reached 91.95% under optimal conditions, offering an eco-friendly alternative for biodiesel production and contributing to waste reduction in the palm oil refining process.

4.2. Bioethanol

Bioethanol production from forestry and agricultural bio-waste has emerged as a prominent and sustainable strategy, drawing attention to its environmental and economic merits (Figure 5) [100]. This intricate process involves the transformation of lignocellulose biomass, such as crop residues, wood chips, and sawdust, into bioethanol via a sequence of enzymatic and microbial fermentation stages. A central challenge within this framework lies in effectively deconstructing the intricate lignocellulose matrix to liberate fermentable sugars. Breakthroughs in pretreatment methods, including steam explosion, acid hydrolysis, and enzymatic digestion, have played a pivotal role in augmenting the accessibility of cellulose and hemicellulose constituents, thereby facilitating subsequent fermentation [101]. Moreover, the evolution of resilient microbial strains, such as genetically engineered yeast and bacteria, adept at efficiently fermenting a diverse spectrum of sugars and withstanding inhibitory byproducts generated during pretreatment, has significantly bolstered bioethanol production yields. These progressive strides in bioethanol production from forestry and agricultural bio-waste contribute to waste reduction and greenhouse gas emission mitigation and establish a sustainable biofuel source.

Using forestry and agricultural bio-waste for bioethanol production presents many environmental advantages. Firstly, it combats the pervasive issue of bio-waste accumulation within the forestry and agricultural sectors. This strategy effectively addresses the dual challenges of waste management and energy generation by converting these residual materials into bioethanol, a sustainable and cleaner energy source. Furthermore, bioethanol is an environmentally friendly alternative to fossil fuels, characterized by a reduced carbon footprint, making a notable contribution to climate change mitigation [102]. Deploying bioethanol derived from bio-waste in various applications, including transportation and as a gasoline blend, can reduce greenhouse gas emissions since it qualifies as a carbon-neutral fuel sourced from sustainable biomass reservoirs [103]. Adopting innovative green utilization methodologies for transforming forestry and agricultural bio-waste into bioethanol signifies a promising pathway toward fostering a more sustainable and circular economy. This approach effectively converts waste into valuable resources, benefiting the environment and the economy.

Bioethanol is currently the most widely used biofuel, and extracting bioethanol from biological waste is a promising way to solve various environmental and energy crises [104]. Bioethanol can be used as an alternative to gasoline to reduce greenhouse gas emissions and air pollution when blended with gasoline as an additive. Obtaining bioethanol from bio-waste is a promising route to address various environmental and energy crisis problems [105]. The process of producing bioethanol from forestry and agricultural bio-waste depends on the type of waste. This process generally includes the following five stages: pretreatment, hydrolysis, fermentation, distillation separation, and purification. As an important component of biological waste gasification, pretreatment plays a fundamental role in the utilization process of biological waste and significantly impacts ethanol yield and production costs. Suitable and effective pretreatment can increase the hydrolysis yield while reducing the crystallinity of cellulose crystals. During hydrolysis, acids or enzymes convert cellulose fibers into smaller biomolecules—glucose monomers. Fermentation uses yeast or bacteria to convert glucose monomers into ethanol. The products obtained from the fermentation process are separated and purified by distillation to produce bioethanol [106].

Pretreatment significantly affects the amount of ethanol yield and production cost [107]. Because of food security concerns, alternative non-food crops are being studied to replace corn starch, the main feedstock for bioethanol production (Table 2). Using an integrated biological approach, ethanol conversion efficiencies of 100% and 96% from the flour of small rye and sorghum grains have been achieved, respectively. These crops were converted to ethanol using a highly efficient starch hydrolysis strain without nitrogen addition [108]. Microalgae can be used to produce bioethanol by yeast fermentation, and the production efficiency of bioethanol can be improved by adding certain poplar branches to the fermentation process. Alfonsin et al. investigated the potential of industrial algal waste to produce bioethanol. Saccharomyces cerevisiae was used to convert industrial algal waste hydrolyzed products to bioethanol with an efficiency of 75%. Moreover, the residue generated during acid hydrolysis had the potential to act as a sustainable solid fuel [109]. Ballesteros et al. [110] studied the production of ethanol from pretreated wheat straw with a steam explosion. The best pretreatment conditions to obtain the highest ethanol yield were 180 °C and 10 min in acid-impregnated straw. Nguyen et al. [107] evaluated the effectiveness of popping pretreatment on the saccharification and fermentation of individual and mixed biomass. The results showed that the popping pretreatment could improve individual and mixed biomass saccharification efficiencies. Shaheen et al. [111] explored the use of low-intensity pulsed ultrasound technology (LIPUS) to improve the metabolic activity of microorganisms for the high-yield production of bioethanol. Their results indicated that LIPUS (1.5 MHz, 80 mW/cm² spatial peak temporal average intensity, 20% duty cycle) could increase bioethanol production from lignocellulose biomass up to 52 ± 16 wt%. Pine needle waste biomass is a kind of troublesome forest biomass in the middle region of the Himalayas, which can lead to forest fires and destroy the ecological environment of the Himalayas. However, this forest waste biomass can be used as an important biological resource for the production of bioethanol, and the use of this waste resource can reduce the occurrence of forest fires while reducing the cost of biofuel production [112].

4.3. Biogas

The conversion of forestry and agricultural bio-waste into biogas has garnered significant attention because of its potential as an environmentally sustainable and economically feasible solution. Bio-waste, encompassing materials like crop residues, forestry remnants, and animal manure, is inherently rich in organic matter. It can be transformed into biogas through anaerobic digestion, primarily methane and carbon dioxide [113]. This not only eases the environmental impact of bio-waste disposal but also offers a renewable energy source. The efficiency of biogas production from bio-waste is contingent on several factors, including the composition of the feedstock, operational conditions, and microbial activity within the anaerobic digester [114]. Strategic optimization of these variables, combined with innovative techniques like co-digestion and pretreatment methods, can enhance biogas yield and quality, rendering it an attractive prospect for sustainable energy generation while concurrently decreasing the environmental footprint of bio-waste management [115].

An inherent advantage of harnessing forestry and agricultural bio-waste for biogas generation lies in its potential to support a circular economy model. The residual digestate derived from the anaerobic digestion process is a valuable organic fertilizer, effectively closing the loop in nutrient cycling and promoting sustainable agricultural practices. Furthermore, the carbon-neutral characteristics of biogas produced from bio-waste play a pivotal role in curbing greenhouse gas emissions and bolstering climate change mitigation endeavors [116]. The versatility of biogas extends to its application in heat and electricity generation and its role as a renewable fuel in the transportation sector. Nevertheless, addressing challenges related to the diverse nature of bio-waste feedstocks, potential contaminants, and the variability in biogas production rates necessitates ongoing research and innovative technologies. Overall, utilizing forestry and agricultural bio-waste for biogas production holds substantial promise for advancing sustainable waste management and green energy production, seamlessly aligning with the core principles of the circular economy and environmental conservation.

Biogas derived from bio-waste is poised to play a critical role in future energy. Its application helps reduce the consumption of hydrocarbons, providing environmentally friendly energy solutions that mitigate pollution [117]. Hence, many countries are investing in alternative technologies for biogas production from biomass and bio-waste. Anaerobic digestion is reported as one of the most effective technologies for treating bio-waste and producing biogas, which can be used as an alternative fuel to liquid petroleum gas and natural gas [118,119]. Anaerobic digestion involves the following four main stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. This technology is effective in reducing odorous compound emissions [120]. Overall anaerobic digestion of bio-waste for biogas production involves pretreatment, waste digestion, gas recovery, and residue treatment processes. Bio-waste residues after anaerobic digestion can be applied to agricultural land as bio-fertilizers, replacing artificial or mineral fertilizers [121,122].

Biofuels derived from green waste, which includes lignocellulose residues such as branches, leaves, tree trimmings, hedge cuttings, and grass clippings, undergo pretreatment, enzymatic hydrolysis, fermentation, and subsequent production of biogas and bioethanol through anaerobic digestion and alcohol fermentation, respectively. Research indicates a maximum biogas yield of 267.1 mL biogas/g dry substrate can be achieved [123]. Investigation into agricultural biogas production potential and technology reveals that biogas holds significant application value for large- and medium-sized farms. With the increase in biogas produced by various agricultural biomass wastes, such as livestock and poultry manure, many studies have made useful discoveries in the development of biogas purification and upgrading technologies [124,125]. Biogas purification and upgrading technologies mainly include solvent washing (after absorption), adsorption processes, low-temperature separation, biological or thermal catalytic hydrogenation processes, and membrane separation. Algal organisms are readily available and can be cultured by various methods. Their potential in bioenergy production has been developed and recognized. By studying algae as a feedstock for biogas production, fossil fuel consumption can be reduced [126]. The anaerobic co-digestion of food waste and algae was found to offset the disadvantages of the single digestion of each substrate, resulting in a maximum methane yield of 334 mL CH₄/g COD input, significantly improving methane productivity and process stability [127]. The development of low-cost biogas technology in recent years has made it possible to convert many untapped agricultural biomass wastes into biogas for use as renewable heat energy, thus achieving the goal of energy savings. Industrial organic waste is increasingly used in biogas plants [128]. Low-cost biogas technology produces biogas using biomass waste from abundant and readily available sources. This improves the reusability of energy [125].

4.4. Hydrogen Production

The sustainable production of hydrogen, recognized as a clean and adaptable energy carrier, has attracted substantial interest in recent years because of its potential to reduce greenhouse gas emissions and advance the shift towards renewable energy sources. An innovative approach within this context involves harnessing forestry and agricultural bio-waste as feedstock for hydrogen generation, commonly called biohydrogen production. This method capitalizes on the abundant organic content in bio-waste materials and leverages biological and thermochemical pathways to convert them into hydrogen gas. Specifically, the breakdown of lignocellulose components in these bio-wastes occurs through the involvement of microbial consortia or by subjecting them to pyrolysis and gasification processes, producing hydrogen-rich gases, including methane and syngas [129]. Subsequent purification and hydrogen separation techniques can yield high-purity hydrogen suitable for various applications, encompassing fuel cells and various industrial processes.

Utilizing forestry and agricultural bio-waste for hydrogen production presents a dual environmental advantage [130]. Firstly, it provides an eco-conscious solution for managing bio-waste materials, mitigating the release of methane, a potent greenhouse gas, which would otherwise occur if these materials were incinerated or left to decompose. Secondly, generating hydrogen from bio-waste is inherently renewable and carbon-neutral. Carbon dioxide emissions during hydrogen production can be effectively balanced by the absorption of carbon dioxide by plants during their growth, creating a closed carbon loop [131]. Furthermore, the adaptability of production methods and the versatility of feedstock sources make this approach particularly appealing, especially in regions with forestry and agricultural resources. Nevertheless, it is essential to acknowledge that process efficiency, cost-effectiveness, and scalability challenges must be diligently addressed to facilitate the widespread adoption of bio-waste-derived hydrogen. Addressing these challenges through dedicated research and development efforts is imperative to harness the full environmental and sustainable benefits of hydrogen production.

Developing biohydrogen production to replace some fossil fuels has enormous economic and environmental benefits [132,133]. There are two main methods for producing hydrogen from biomass waste. The first is a microbial method, which can be divided into anaerobic fermentation and photosynthetic organisms to produce hydrogen. The second method is via thermochemical conversion. The thermochemical conversion method for hydrogen production is divided into pyrolysis, hydrogenification, and super-zero hydrogen production. Fermentative hydrogen production has recently been studied to convert bio-waste and wastewater into hydrogen and has received increasing attention worldwide [134,135,136]. To explore methods of increasing hydrogen production from fruit wastes, Akinbomi et al. [137] assessed the hydrogen production potential from the fermentation of a single fruit compared to the fermentation of mixed fruits. The hydrogen yield was increased for all feedstock when the digester was operated at a hydraulic retention time of 5 days. Over a billion metric tons of food waste are generated each year. This food waste has become an environmental problem for many countries. Developing a good way to utilize this food waste is one of the major global challenges. Han et al. [138] developed a novel hydrogen production method that combined solid-state fermentation and dark fermentation to increase hydrogen yield. This novel bioprocess could effectively accelerate the hydrolysis rate, improve food waste utilization, and enhance hydrogen yield.

Using lignocellulose raw materials such as wheat and corn straw, biohydrogen can be obtained by thermochemical methods such as pyrolysis and gasification or by biological methods such as fermentation and photobiological methods [139,140]. Hydrogen production from microalgae is considered a green and developable energy production method that can alleviate fuel shortages and recycle waste. Although the hydrogen production of algae has low energy consumption and simple pretreatment, the hydrogen production is low. Multiple engineering studies on algae biohydrogen production show that with the understanding of algae genome sequences and metabolic functions, as well as the development of advanced tools and software, the combination of genetic engineering and bioinformatics will undoubtedly contribute to the development of microalgae strains that are more suitable for biohydrogen production than those currently available [141].

Carbohydrate-rich biomass waste can be a solid substrate for solid fermentation and dark fermentation to produce biohydrogen. Solid-state fermentation (SSF) is a fermentation process in which there is no or almost no free-flowing liquid and microorganisms grow and metabolize on a solid substrate [142], which has the effect of increasing the content of bioactive compounds, reducing some processing costs, and reducing environmental pollution [142]. Dark fermentation hydrogen production technology involves the combination of facultative organisms and obligate anaerobic bacteria to produce hydrogen after a biological reaction using algae, which requires a simple reaction vessel with high productivity [143]. More than 1 billion tons of food are wasted every year. This food waste has become an environmental problem in many countries. Han et al. combined solid fermentation with dark fermentation for kitchen leftovers, which can accelerate the hydrolysis rate of kitchen waste, improve the utilization rate, increase the hydrogen production rate, effectively utilize kitchen waste to a certain extent, and save the consumption of other biological resources.

4.5. Biocatalyst

The utilization of forestry and agricultural bio-waste for biocatalyst production holds substantial promise, addressing both the imperative of waste reduction and the pursuit of sustainable enzymatic applications. Recent years have witnessed remarkable strides in unlocking the latent potential residing within these bio-waste resources. Lignocellulose materials, exemplified by crop residues and woody biomass, contain a wealth of lignin, cellulose, and hemicellulose, amenable to enzymatic depolymerization for the generation of valuable enzymes [144]. Enzymes sourced from such substrates have consistently exhibited impressive attributes in terms of stability, specificity, and catalytic efficiency. Moreover, the environmentally conscious profile of biocatalysts originating from forestry and agricultural residues harmonizes with the precepts of green chemistry, providing an eco-friendly alternative to conventional chemical catalysts. This holistic approach not only confronts the challenge of bio-waste management but also fosters the advancement of sustainable bioprocessing methodologies for an array of industrial applications.

The utilization of forestry and agricultural bio-waste for biocatalyst production is bolstered by a spectrum of pioneering eco-friendly techniques. These methodologies encompass initial pretreatment steps, which serve to eliminate lignin, enhancing the accessibility of cellulose and hemicellulose for subsequent enzymatic degradation [145]. Additionally, biocatalyst performance benefits from enzyme engineering and optimization procedures specifically tailored to bio-waste sources. Furthermore, the domain of bioprocess engineering and downstream processing has proven indispensable, leading to notable advancements in the overall efficiency and yield of biocatalyst production from these sustainable resources [146]. The effective amalgamation of these innovative strategies not only diminishes the ecological footprint associated with bio-waste management but also provides an avenue for the economical and environmentally responsible production of biocatalysts, spanning various industries, including biofuels, textiles, and pharmaceuticals. This comprehensive review expounds on these eco-friendly utilization approaches, shedding light on the latent potential of forestry and agricultural bio-waste within the biocatalysis realm.

Using sustainable bio-waste-derived hydrate materials as low-cost and ecologically and environmentally friendly metal-free carbon photocatalysts has great potential applications in selective photocatalytic organic synthesis in the future. Through a clean and environmentally friendly strategy, carbon hydrate prepared from biological waste was used as the first metal-free biochar catalyst [147]. Also, Acai seed ash (ASA), a low-cost and readily available seed waste studied by Mares et al. [148], is used to exchange methyl esters in soybean oil. Because of its high metal oxide and alkaline surface site carbonates, ASA has catalytic activity, and the synthesized catalyst can contain more than 92.5% ester. The rich oxygen-containing functional groups embedded in the surface can provide active sites for photocatalysis, and the main active sites are the diphenol hydroxyl functional groups and quinone parts attached to the large π electron system. The carbon catalyst has excellent photocatalytic activity and reusability for various amines’ selective oxidative coupling reactions under visible-light irradiation [149].

Xu et al. used biomass such as glucose, sucrose, starch, cellulose, and paperboard to convert to a hydrothermal carbonaceous carbon (HTCC) photocatalyst for H₂O₂ synthesis in pure water [150]. The apparent quantum yield and synthesis rate could reach 18.2%. Importantly, HTCC can be prepared from biomass waste, such as cardboard. Their study provides insight into oxygen activation in emerging HTCC photocatalysts and highlights their role in H₂O₂ synthesis in pure water. Abundant biomass waste such as rice husks, corn husks, and hazelnut husks can be used to synthesize carbon materials. Sugarcane, India’s second-largest seasonal crop, can be processed to extract sugar, while bagasse byproduct can be used to produce carbon-like materials. Doke et al. [151] synthesized and characterized carbon spheres from readily available bagasse and D-glucose for comparison and the covalent functionalization of organic amines on carbon surfaces by condensation of hydroxyl with trimethoxysilane. A solid-base catalyst was successfully prepared using the Henry reaction catalyst. Using jasmine waste as a precursor, Xiao et al. [152] prepared a new biochar material (JWB) by the high-temperature carbonization method, which can effectively activate PMS to promote TC degradation and realize the strategy of one waste, one treatment. Their study provided efficient and green biomass as a raw material peroxo sulfate (SR-AOPs) catalyst for the treatment of refractory organic wastewater and provided a new strategy for the resource utilization of jasmine waste.

Catalysts can be extracted from agricultural waste to improve the efficiency of transesterification and optimize the biodiesel production process [153]. Using agricultural and industrial ginger straw waste as raw material, a green heterogeneous acid catalyst was prepared by partial carbonization, and then an acid catalyst was prepared by sulfuric acid sulfonation [154]. When methanol and oleic acid were used for esterification, the catalytic esterification conversion rate could reach 93.2%. Biodiesel production requires homogeneous or heterogeneous catalysts as reactants for esterification exchange reactions. Bio-based heterogeneous catalysts can be synthesized from biological wastes rich in calcium and potassium. Compared with homogeneous catalysts, they are recyclable and environmentally friendly. The ash of banana stems converted into bio-carbon at high temperatures by calcination can be used as a heterogeneous catalyst for biodiesel production from waste edible oil [155].

Overall, converting forestry and agricultural bio-waste into value-added chemicals and bioenergy is a sustainable method of bio-waste management. Bioethanol made from agricultural bio-waste offers significant environmental, socioeconomic, and strategic benefits. Complete utilization of agriculture bio-waste could produce 16 times more ethanol than the current global production. It is reported that approximately 205 billion liters of rice straw, 104 billion liters of wheat straw, 58.6 billion liters of corn straw, and 51.3 billion liters of sugarcane bagasse are produced annually. Currently, biodiesel from soy, rapeseed, and oil palm dominates the biofuel market.

5. Application of Biowastes in Other Areas

Bio-waste is a valuable resource for many locations. It must be well utilized at the source to turn this waste into a valuable resource. Bio-waste, such as crop straw, kitchen waste, and industrial bio-waste, contains many nutrients and can be used as animal feed. Physical, chemical, and biological processes improve the palatability and nutritional value of bio-waste such as wheat straw, rice straw, fruit, and food waste. This method reduces the cost of animal feed and provides high-quality organic fertilizer by utilizing animal manure in fields. At present, straw feed is widely used in ruminant breeding.

Lactic acid is the most widely occurring hydroxyl-carboxylic acid in nature and is a key component in the production of poly(lactic acid), one of the most promising biodegradable plastics. However, the use of pure sugars as the carbon source for lactic acid production significantly increases production costs, posing a major bottleneck in the biotechnological production of optically pure lactic acid. Forestry and agricultural bio-waste can be used as substrates for lactic acid fermentation, providing a more cost-effective solution. Bacterial polyhydroxyalkanoates (PHAs), another major class of bio-based plastics, are intracellularly produced by the PHA synthase-catalyzed polymerization of hydroxyacyl-CoAs. Thygesen et al. [156] demonstrated that biological waste could yield up to 12 g/L/h of lactic acid through distillation and emulsion liquid membrane separation. Similarly, Azaizeh [157] and Ahring [158] produced lactic acid from various types of lignocellulosic biomass, such as Carob and corn straw, achieving maximum yields of 3.2 and 3.69 g/L/h, respectively, through hydrolysis and continuous fermentation under different conditions. PHAs can also be produced from agroforestry bio-waste rich in polyphenols, carbohydrates, and pectin [159]. Arreola-Vargas et al. [160] pretreated bagasse from agave to increase its lignocellulose fraction, boosting PHA production from 0.09 g/L to 0.97 g/L, suggesting a new approach for producing high-quality bioplastics. In addition, biological waste such as cassava waste can be used as a substrate for the production of butanol [161].

Composting is a simple and rapid decomposition process of organic matter under controlled and aerobic conditions. It is divided into aerobic and anaerobic composting according to the environment in which microorganisms grow. Composting technology is an environmentally acceptable way to dispose of and utilize bio-waste. Thus, it has been widely applied to bio-waste such as yard bio-waste, kitchen bio-waste, and agricultural bio-waste [162,163]. Composting fertilizer is the humus complex obtained by composting biomass waste. It has also been reported that the co-composting of biomass wastes can produce useful compost.

Biochar is produced by the pyrolysis of biomass under limited oxygen conditions. The application of biochar in the composting of biomass waste has recently attracted the attention of researchers. The nutrient content of the compost product was greatly increased by blending green waste with waste mushroom compost and biochar. In addition, the quality of the compost was also improved [164]. However, odor emission is one of the major problems with composting bio-waste. New approaches have been proposed for managing and utilizing biomass waste. Bio-waste can be used as a raw material for biochar production. Biochar has the potential to be an inexpensive adsorbent that can store some of the most common environmental pollutants. Chromium-complexed collagen is generated as waste during the processing of skin into leather. Ashokkumar et al. [165] reported a simple heat treatment process to convert this hazardous industrial waste into core–shell chromium-–carbon nanomaterials. The results showed that these core–shell nanomaterials can potentially be utilized in electromagnetic interference (EMI) shielding applications or as a catalyst in the aza-Michael addition reaction. These high-value Cr carbon core–shell nanomaterials from leather waste have great potential for various applications. Zequine et al. [166] developed an efficient, flexible supercapacitor obtained by carbonizing jute, which was treated with a facile hydrothermal method and chemical activation. Using this carbonized jute, the supercapacitor device fabricated showed a promising specific capacitance of about 51 F/g.

6. Conclusions and Perspective

This review starts with the categorization of forestry and agricultural bio-waste and critically examines the environmental issues and resource waste associated with traditional methods such as landfilling and incineration. It focuses on common agricultural waste like wheat straw, corn stalks, sorghum straw, rice straw, soybean stalks, cotton straw, rice husk, and wheat husk, as well as forestry biomass waste including twigs, leaves, wood shavings, sawdust, sawdust, and branches. This review highlights the potential of agroforestry biomass waste due to its unique structural properties, noting its usefulness as additives and reinforcements in composite materials, as substitutes for fossil energy, and as fertilizers.

Cellulose, proteins, polysaccharides, and other components in forestry and agricultural bio-waste can be used as additives and adhesives in various composite materials, including papermaking, natural fiber–polymer composites, sheet processing, and film-coating materials, which greatly reduces the cost of composite material preparation, improves material performance, and reduces environmental pollution. Utilizing wood fiber feedstock from agroforestry biomass waste can also alleviate pressure on slow-growing forests. Despite the successful application of agroforestry waste in producing high-performance particleboard or fiberboard, several challenges still persist in the manufacturing process. Urea–formaldehyde resins are commonly used as adhesives in particleboard and fiberboard manufacturing because of their cost cost-effectiveness. However, the release of formaldehyde release poses a problem with these adhesives, highlighting the need for the development of environmentally friendly adhesives. Agroforestry biomass waste, which contains numerous hydrophilic groups (such as hydroxyl groups), often results in particleboard and fiberboard with poor water resistance. This necessitates careful selection of adhesives and optimization of the hot-pressing process. Utilizing agroforestry waste to modify polymer composites can lower production costs and promote resource recycling. However, this approach usually adversely affects the mechanical properties of the composites, as the poor compatibility between natural fibers and polymer can lead to agglomeration during processing, thereby impacting the overall performance of the composites.

Forestry and agricultural bio-waste can be converted into clean energy sources such as diesel, ethanol, biogas, and hydrogen through biochemical and thermochemical methods. These wastes can also serve as substrates for cultivating beneficial molds and bacteria, boosting the efficiency of biocatalysts and promoting advancements in biofuel and textile production and the pharmaceutical industry. Current key research trends include safe treatment of bio-waste, reduced reliance on fossil fuels, and optimized recycling processes within the forestry and agricultural sectors. Pretreatment is crucial for breaking down complex structures in biomass waste, enabling the production of diverse biofuels and composites. Achieving desirable results with various types of agroforestry biomass waste poses a significant technical challenge, particularly regarding the suitability of treatment methods, equipment requirements, and energy consumption. Therefore, a thorough understanding of the pretreatment process and the development of innovative, sustainable strategies are essential. In addition, advancements in finding or developing thermophilic strains that thrive under harsh conditions, optimizing fermentation parameters, and establishing large-scale integrated biorefinery plants are vital for the large-scale production of biofuels like ethanol, methane, and biogas through microbial fermentation. Implementing new technologies for the integrated treatment of agroforestry biomass waste will not only enhance waste management but also fulfill material and energy demands. The utilization of existing refinery facilities is crucial for the technical and economic feasibility of large-scale development of bioenergy, facilitating a transition from fossil fuels to greener bioenergy and supporting a circular bioeconomy.

Currently, a significant amount of forestry and agricultural bio-waste remains underutilized. This is partly due to the improper classification and management of forestry and agricultural bio-waste, resulting in mixed types of bio-waste that complicate their efficient utilization. Furthermore, efficient utilization of forestry and agricultural biomass waste involves high temperatures, high pressure, and microbial fermentation, which poses certain safety hazards and can lead to secondary environmental pollution. Therefore, there is an urgent need to improve waste classification and advance key technologies for pretreatment, hydrolysis, fermentation, and purification to make this bioenergy more promising. To enhance the utilization of forestry and agricultural bio-waste, some recommendations are proposed. Developing high-tech R&D for bio-waste and using policy tools and market mechanisms to mobilize enterprises to reuse forestry and agricultural bio-waste will be essential steps in this process.