In the direction of a sustainable future: A Comprehensive Review of Evolution, Environmental Impacts, and Future Prospects of Bioenergy

: As global focus sharpens on carbon emissions and environmental protection; the pursuit of sustainable development permeates every sector. Against the backdrop of increasing fossil fuel prices and relentless energy demand, the exploration of clean energy has become paramount. This paper presents a comprehensive review of bioenergy. It introduces the concept and underscores its importance, tracing the historical stages and accomplishments in its development. The paper explicates different types of bioenergy and their chemical operating principles. The integral system of bioenergy is also evaluated, focusing on crucial components: bioenergy feedstocks, processing technologies, transport process, storage, and grid integration. The paper concludes with an assessment of bioenergy's economic and environmental impacts, considering market dynamics and future prospects, and suggests potential mitigation measures against its environmental repercussions.


Introduction
Bioenergy, a renewable energy derivative from organic materials, offers a potential solution to global energy quandaries and climate change.This paper probes the history, design principles, market dynamics, and environmental consequences of bioenergy, highlighting its role as a critical form of renewable energy.Bioenergy is derived from various biological sources such as plants, animals, and microorganisms, and transformed into heat, electricity, and biofuels.As a versatile and sustainable energy source, bioenergy can curb emissions, enrich the energy mix, and invigorate rural development.Bioenergy plays a significant part in global energy configuration.By 2019, biomass energy constituted roughly 5% of the global primary energy consumption, the fourth-largest energy source following oil, coal, and natural gas [1].Biomass also has a unique role in some regions like the European Union, where it forms nearly 60% of renewable energy consumption [2].The application of biomass energy varies across sectors.In the residential and commercial sectors, it primarily offers heating, while in the industrial sector, it generates both heat and electricity.Biomass-derived biofuels like ethanol and biodiesel find use in the transportation sector as supplements to traditional fuels [3].In this paper, the developing history of bioenergy is mentioned.Furthermore, current design principles and components of biomass energy systems are introduced.Lastly, the economic and environmental values of biomass energy systems are included.Compared to other reviews, this paper not only focuses on the technological principle of bioenergy but also introduces the bioenergy product, implemented technology in different bioenergy products, transport process and considerations of storage to conclude the components of the bioenergy system.In addition, the economic values and environmental impacts of bioenergy are considered to evaluate the importance of bioenergy and the advantages of developing bioenergy in achieving sustainability.

The History of Biomass Energy
Biomass energy, a long-standing form of energy, has served humans for millennia.From early societies using wood for warmth and cooking to contemporary advancements in biofuel production, the evolution of biomass energy has been significant.This section delves into the historical progression of biomass energy, tracing its roots to ancient civilizations where wood and organic materials were burned for basic needs.These early practices laid the groundwork for future developments.During the Industrial Revolution of the 18th and 19th centuries, burgeoning energy demands led to a surge in coal and fossil fuel usage.Regrettably, reliance on these conventional energy sources resulted in environmental degradation and air pollution.Around the same time, biogas-a gaseous fuel produced by the anaerobic digestion of organic matter-surfaced as a viable alternative to traditional fuels [4].As awareness of the environmental impact of fossil fuel combustion expanded in the 20th century, research and development in biomass energy gained momentum.The establishment of the first commercial biodiesel plant in the 1990s marked a critical juncture in biomass-derived biofuel production [5].Technological advancements enabled more efficient biomass conversion into heat, electricity, and biofuels.
Over the late 20th and early 21st centuries, these advancements culminated in the emergence of advanced biomass energy conversion technologies, offering more efficient and environmentally friendly ways to harness biomass energy [6].The figure below uses a timeline to conclude the historical development of Biomass energy (Figure 1).

Current Design Principles of Biomass Energy
Biomass resources and technologies are gaining attention over the past decades because the use of them reduce greenhouse gas emission significantly.It accounts for at least 10% of total human energy use and is especially consumed in developing countries which covers approximately a third of total primary energy consumption [7,8].Among countries with well-developed forestry industries, biomass accounts for an important and rising energy source with advanced conversion technologies [9].The various forms of biomass feedstocks as well as the efficiency of current technologies to convert biomass to bioenergy are examined to optimize the production of bioenergy as a renewable source.
The biomass utilized as feedstock for bioenergy production is generally classified as terrestrial or aquatic.For the terrestrial biomass feedstock, the first type is mainly food crops including maize, sugarcane, soybean, etc.This type of feedstock is the most used because of the mature technologies and their effective yield of bioethanol and biodiesel due to rich sugar or lipids.Compared to the possible disadvantages to food economics from massively using these food crops as energy sources, the terrestrial cellulosic biomass feedstocks are acquired from agricultural residues of non-food origin and forest residues [10].Aquatic biomass consists of either microscopic or large photosynthetic algae and cyanobacteria living mainly in water.Through the chemical process of photosynthesis and floating in an environment of rich nutrition, the aquatic biomass can support much more rapid growth than the terrestrial feedstock.Aquatic biomass has the advantages of high aridity and salinity tolerance and high containment of lipids and triacyl glycerides to boost the production of renewable liquid fuels [11].The mechanism of the conversion of natural resources to plant biomass is based on photosynthesis, the process is represented by the chemical equation below: Glucose is one of products for photosynthesis that builds essential plant biomass including starch, cellulose, lipids and proteins in subsequent reactions, and the rich chemical energy stored in these products is usually released as heat through combustion, which is inefficient and polluting.Therefore, various systems for conversion technologies are designed to improve bioproduct conversion efficiency, and the technologies are catagorized according to the solid, liquid, or gaseous form of energy products produced, corresponding to bioethanol, biodiesel, and biogas.The sugar and xylose fermentation by microorganisms produced bioethanol and then separated from the mixture via heating or distillation.In order to improve the efficiency of producing bioethanol from cellulosic plant materials, effective pre-treatments are continuously developed to depolymerize cellulose and hemicellulose components using ionic liquids to increase cell wall accessibility [12] and enzymes for ethanol conversion [13].
Biodiesel, another form of feedstock, is a mixture of fatty acid alkyl esters (FAAE) produced through trans/esterification. Enzymatic biodiesel production has shown benefits including the low requirement for energy, high conversion efficiency of oil with abundant free fatty acid (FFA) contents, high purity of glycerol by-product, and convenient product separation and reuse due to stationary enzymes.
Biogas is usually produced as hydrogen and methane.Biohydrogen is generated anaerobically through the fermentation of microorganisms such as Clostridium and Enterobacter, [12].Methane, the other form of biogas and generated by microbes that use organic acid as a substrate to generate.system There are four general components are play important roles in the biomass energy system which are feedstocks of biomass, processing, transmission, and storage.All the components in the bioenergy system follow a top-tobottom direction of operation.Transport and storage is part of the system integration into the energy grid, and the next section of this paper will introduce them in detail.The whole system starts from the feedstocks of biomass, different feedstocks of biomass also lead to different types of biomass products which are solid biomass and fluid biomass.However, not all biomass feedstocks can be used directly; it needs to be processed to optimize biomass performance and increase energy generation efficiency while reducing pollution.Before the mechanical and chemical technologies to convert biomass to feasible biofuel, pre-processing such as cleaning and leaching are required to ensure the purity of biomass and to improve the efficiency of the subsequent treatment.The most common equipment used in cleaning are sieves and magnetic conveyors, they remove dirt, agricultural residuals, and metal in the feedstock and maximize cleanliness.The reason for cleaning is plenty of dirt and impurities will deposit on the plant during the photosynthesis process.Additionally, the process of initial harvesting and collection of biomass exacerbates the uptake of impurities, and excessive impurities can reduce the thermal performance of biomass [14].Cleaning can remove most of the impurities on the surface of biomass, but the intrinsic compounds are necessary to be removed as well.Extractive leaching is one technology used most in the industry to solve this problem.However, some suppliers are considering the economic viability of extractive leaching since it prevents contact between potential bonds which leads to a reduction in the strength and durability of the product [15].After pre-processing of biomass, the conversion treatment from biomass to solid biomass product include mechanical and chemical treatment respectively.Mechanical treatment is mainly dedicated to improving the quality and thermal performance of solid biomass such as controlling the moisture content and the particle size.Chopping is one of the physical treatments that reduce bulk feedstocks of solid biomass to a manageable size and improves the efficiency of combustion.Chopping feedstocks to a size of less than 10mm can significantly improve the efficiency and quality of solid products [16].
Torrefaction is one typical chemical treatment for the densification of biomass to improve the thermal oxidation behavior [14].The process of torrefaction effectively decreases the volatile matter content and increases the surface area of biomass [17] which enhances the efficiency of energy conversion during combustion.However, the advantages and disadvantages both significantly exist in the process of torrefaction, the release of moisture and the degradation of polymers in the plant could lead to friction increase in the process of pelleting.High pressures lead to high rates of wear and tear on the machine, and the high heat generated by high pressures can lead to fires or clogging of the machine.But high pressure in turn gives the product better durability and strength [14].Thus, it is crucial to use the right temperature range during torrefaction.
Different from the solid biomass product, the fluid biomass product required more steps to process, and it starts from the processing of generating intermediates and ends up with the generation of the final biofuels.Most biomass conversion is held in the biorefinery, and it is stated that biochemical and thermochemical technologies are used commonly in industries [18].Hydrolysis is one of the typical biochemical technologies and pretreatment is essential for it to break out the plant cell and make sure further deconstruction during the hydrolysis.The source of hydrolysis is mainly sugaring canes and fermentable sugar and glucose are released as intermediate during the chemical reaction [11].Additionally, the difference between the biological and chemical processes of hydrolysis is the reactants.A catalyst is introduced to the chemical processing which improves the efficiency of fermentation rather than adding fermenting microorganisms to the biomass of hydrolysates.Additionally, gasification and pyrolysis are two typical thermochemical technologies that combine catalysts with high temperatures to change the physical characteristics and chemical structures of the feedstocks of biomass.Gasification decomposed lignocellulosic under a no oxygen and high-temperature environment.Then raw syngas, which is a type of intermediate are generated during oxidation, but a gas cleanup process is needed to remove impurities of the raw syngas [19].After generating relatively pure syngas, it can be added to the process of synthesis of biofuels.Generally, syngas can generate fluid biofuels such as methane and hydrogen by running the process of methanol synthesis and water-gasshift [11].Furthermore, pyrolysis also reacts with biomass in no oxygen conditions but under lower temperatures than gasification.The intermediate like pyrolysis can generate pyrolysis oil and needs filtration to keep the cleanliness and purities of products.Then biofuels with lower oxygen content can be generated by reacting with pyrolysis oil during the process of hydrotreating and hydrocracking [20].Each type of biomass product and processing has different characteristics, and the selection of biomass product depends on the demands and acceptable economic investment of industries.As mentioned above, transport and storage are the two main components of a biomass energy system, and they are also primarily responsible for integrating the energy generated from biofuels into the energy grid.The general structure of the integration of biofuel-generated energy into the energy grid is that biomass feedstock is collected from different locations, and then transported to a biorefinery.They can be converted into biofuel, and finally, the biofuel is transported to a power plant and undergoes combustion to convert biofuels into energy (Figure 2).Biomass energy has a significant challenge for transport which is the cost is very expensive because of the low density and inhomogeneity of biomass feedstocks.Furthermore, some of the woody biomass feedstock comes from the forest and some of the crops or crops residues come from the farm, so the location of the biomass feedstocks is more dispersed which makes it more expensive to transport them to a biorefinery.
Additionally, densification affects the value of biofuels and decreases the cost of transporting and storage when operating densification before transport [21].However, more experimental data are needed to support the above claims and explore the feasibility.Additionally, the distance between biofuel mass suppliers and biomass processing facilities is considered to decrease the cost of transportation.Yue et al. [11] conducted a design that resulted in three scenarios of spatial relationships between biomass suppliers and integrated biorefineries.They designed a centralized scenario, where one integrated biorefinery is in the central area of the biomass supplier; a distributed scenario, where four integrated biorefineries are evenly distributed in the biomass supplier's area; and a two-stage scenario, where pretreatment facilities are evenly distributed in the corners of the biomass supplier's area and one upgrading facility is centrally located.The total cost of the three scenarios operating in different biomass supplier area sizes was obtained, and the results showed that the two-stage scenario had the lowest cost for most of the biomass supplier area sizes.However, the efficiency of converting biofuels to electricity is relatively lower than in other scenarios.Storage of biomass is crucial to the system's integration into the energy grid as well.The harvest season is on average three to four months throughout a year for some energy crops and agricultural residues.Harvested energy crops and agricultural residues need to be stored in warehouses, however, these crops react with microorganisms and undergo biodegradation, which greatly affects the calorific value of the energy crops and thus leads to a decrease in the performance of the biofuel produced from these crops.Therefore, the storage process requires the installation of fans or heaters [14] or even vacuum and sterilization, which undoubtedly increases the cost.Rentizelas et al. [22] found that storage conditions depend on moisture content.If the moisture content of biomass is low, dry storage would have little effect.Nevertheless, agricultural residues usually have 40-50% moisture content, so they must be collected from the field and stored under dry storage conditions in time to avoid biodegradation.

Economics of Biomass Energy
As advanced technology develops and improves biomass, it is being introduced into the market, with woody biomass occupying the majority of the market.Woody biomass, mostly oaks and pines, cost $36.32 per metric ton in the market of States in March 2022.Production costs include between $500 and $1,500 per kilowatt of thermal energy installed.It is an expensive renewable energy alternative, but biomass does not require a long growth cycle like fossil energy, so the cost of bioenergy will be cheaper than fossil fuel.Biomass costs between $0.05 and $0.06 kilowatts per hour.However, the cost of fossil is around $0.74 per kWh, as biomass has not yet reached economies of scale.Utilization of energy for various purposes is the primary cause of alternative use.In contrast to the renewable nature of bioenergy, the nonrenewable nature of fossil energy leads to its scarcity and expensive price in the future market.Under the policy of carbon neutrality in 2060, eco-friendly behaviour is encouraged; therefore, renewable biomass is a priority for farmers [23], exceedingly affluent families, and urban residents who are permitted to heat with biomass.Figure 3 shows the components of the market in biomass.Compared to other renewable energy categories, biomass is relatively simpler to segment on the market front.Geographical factors, climate, and biomass heating policy are considered as market segmentation conditions.Biomass is available on several continents due to its most basic condition, which is geographical suitability.In addition, because biomass resources are diverse and suitable for most regions, some countries are cultivating their own biomass resources according to their geographical conditions and particular weather climates.
Pines and oaks are utilized and heated as biomass energy in the United States.In regions where the weather is favorable for tree planting, woody biomass plays the primary role among biomass resources.In contrast, nonwoody biomass is prevalent in regions where the weather is unfavorable for tree planting.Cotton is the most common source of biomass in China, and it is primarily planted and harvested in Xinjiang, a region that is conducive to cotton growth.
The biomass energy market is estimated to grow by US$75 billion in value from 2022 to 2023 [24].Cooperating with digital marketing could result in an increase of nearly USD 75 billion due to the industry's high growth rate.On the biomass market, solid biofuel covers 86.0% of the market, followed by liquid biofuel at 12.50% and biogas at 1.50%.Solid biofuel is easier to store than liquid biofuel and biogas; the lower cost of storage and the lower price are the vital factors for solid biofuel's market dominance.Biomass will continue to create hydrogen at scale and play other important roles in hydrogen technology and the economy.
Paper will remain a biomass source for decades since the demand for tissues and sanitary goods.continue to be a source of biomass in the coming decades [25].The number of probable development areas for biomass exhibits a significant amount of growth potential.Biomass emits healthier emissions than fossil fuels, which is one of its greatest advantages.As a result, bioenergy and other forms of renewable energy will be strongly promoted in domestic and industrial applications.

Environmental Impacts of Biomass Energy
Biomass is the matter produced from recently living organisms that are used to create bioenergy.Almost every use of biomass energy results in the emission of CO2 into the atmosphere.CO2 is a greenhouse gas that can trap heat inside the earth and have a negative impact on our environment as it ultimately leads to the issue of global warming.
Bioenergy can also be given into multiple different types of energy, each with its benefits.First biofuels and bioenergy are turned into transportation fuels, which include fuel sources such as ethanol and biodiesel, these are converted to liquid source energy, to meet transportation needs.Second, biopower is the use of technologies, which convert renewable biomass fuels into heat and electricity, through burning, bacterial decay, and conversion of fuels to gasses or fuels.Last is bioproducts, which is the process of converting biomass fuels to chemicals that are useful in creating things like plastic, which is usually made from petroleum [26].These three processes of converting biomass fuel into directly usable energy.Although burning biomass fuels releases about the same amount of greenhouse gases as burning fossil fuels.It is believed that the release of greenhouse gas, CO2, is what the plant before it was fuel has already captured, through the process of photosynthesis.Therefore, the greenhouse gasses that were replaced by the burning of biomass fuel could be considered as "new greenhouse gas" as the released carbon dioxide is largely balanced by the carbon dioxide captured in the plant's growth (just a general idea as it also depends on energy used to grow the plants, harvest, and processing of the fuel).It is also found best to grow biomass in previously cleared land or underutilized farmland.And not opening specific areas for biomass production, such as taking down a forest just to get land to plant biomasses.The other positive effect of biofuels is that biomass fuels can reduce a country's reliance on oil or fossil fuels, as biofuels are the only renewable liquid transportation fuels available today.The production of biofuels also supports agriculture and the forest industry as biofuels are the energy being used to power things like paper mill residue, lumber mill scrap, and municipal waste.These include plants such as corn, soybean, etc. which in future development in the National Renewable Energy Laboratory (NREL) agricultural residues such as corn stover, stalks, leaves, and husks of the plant and wheat straw will also be used for biomass.Long-term, and fast-growing plants such as the greasers, algae, and fast-growing trees could be also used to be dedicated to biomass energy production, the production is low cost and could be accomplished with material of no use.Wood as biomass energy and its negative impact are significant.During the process of burning wood, many chemicals are released.Not to mention the greenhouse gases produced, and the smoke produced by the process of burning wood contains dangerous pollutants like carbon monoxide and particulate matter.One upside of burning wide is its wide use in poor countries, people can still have access to heat through the process of burning wood.The upside of the wide use of burning wood also has a negative impact on the environment.The wood used in the process comes from deforestation, which increased deforestation globally and could raise many other issues in the world, such as droughts, sandstorms, etc.People today harvest wood faster than they plant it.Choosing burning wood has a negative effect.The municipal solid mentioned above also has a negative impact not only on the environment but on people's health, as burning these municipal waste releases chemicals and waste into the air, these chemicals are non-biomass and can be harmful to the people and the environment if not properly controlled, after the burning process [27].That's why people must be careful with the process of burning wood.Some people said that burning wood and making charcoal out of wood could be a replacement for fossil fuel, but the process of burning wood itself is releasing carbon dioxide, a greenhouse gas that could cause global temperature increase and climate change.It is not a very good replacement, as one of the main goals to stop climate change is to reduce the emissions of CO2 into the air, but the process of burning wood does not counteract that.Based on the saying of environmental scientists, humans only have a decade to limit the CO2 emission, further ruling out the possibility of burning wood's biomass energy as a good replacement.Plus, wood is a limited resource, which when not used carefully could run out.As above the consideration of biomass energy as carbon neutral is not simple.The amount of carbon they release depends on combustion technology, how the biomass is harvested, any re-growing efforts, the type of biomass used, timing, and the energy resource it displaces [28].
According to the results from different research, we conclude some strategies to mitigate the negative impact of biomass energy: 1. Sustainable biomass production: Biomass should be produced in a sustainable manner, which involves practices such as crop rotation, responsible land use, and the use of non-food crops for bioenergy.
2. Efficient conversion technologies: Efficient conversion technologies can help reduce the amount of biomass needed for energy production and minimize emissions.For example, advanced gasification and pyrolysis technologies can increase energy efficiency and reduce emissions of greenhouse gases.
3. Carbon capture and storage: Biomass energy can be used in conjunction with carbon capture and storage technologies to reduce greenhouse gas emissions.This involves capturing carbon dioxide emissions from the combustion of biomass and storing them underground or using them for industrial processes.
4. Use of waste materials: Biomass can be sourced from waste materials such as agricultural and forestry residues, which can help reduce waste and provide a sustainable source of energy.
5. Environmental impact assessments: Environmental impact assessments should be conducted before any new biomass energy projects are developed to identify potential impacts and mitigate them.This includes assessing the impact on local ecosystems, water resources, and air quality.
6. Education and awareness: Education and awareness campaigns can help promote responsible biomass energy use and encourage consumers to make sustainable choices.This can include promoting energy conservation and efficiency measures, such as using energy-efficient appliances and reducing energy consumption through behavior changes.

Conclusion and Perspective
In conclusion, bioenergy holds immense potential as a renewable energy source that can help us address global energy challenges, and climate change, and drive sustainable development.By understanding its historical development, design principles, components of the bioenergy system, economic impacts, and environmental impacts, we can develop strategies to harness its full potential and contribute to a sustainable, low-carbon future.Compared to other renewable energy sources, bioenergy has some significant advantages and drawbacks to be considered.Bioenergy has a variety of feedstocks, such as crops and residues, which means that feedstocks are readily available.But at the same time, we need to choose our feedstocks carefully, because if we use a lot of crops, we will lose balance in the economic market for food and consequently other negative social problems.The multiple components of bioenergy and the complex chemical processing steps also add uncertainty to the conversion of bioenergy and the potential reduction of energy conversion efficiency at the processing step.The cost of operation, as mentioned above, can also be increased by the complex structure of the energy system.In terms of the environment, the selection of feedstock and processing methods also need to be done carefully, otherwise, there will be other aspects of environmental pollution as mentioned in the paper.This paper is believed that can give the reader a reference for the concept of bioenergy and the operation and impact of bioenergy systems and based on this do more detailed research related to the optimization of bioenergy operation system steps.For future research directions, we suggest that more specific step optimization and local bioenergy development studies can be done to propose suitable local bioenergy development models by understanding local bioenergy incentives and considering what can be optimized and improved from each part of the bioenergy system, while more experimental data are needed to support and validate the development plans.

Figure 2 .
Figure 2. The transporting and integrating process

Figure 3 .
Figure 3.The components of the market in biomass