Biomass Energy

1. Introduction
Biomass derived products is one of the pillars of transitioning into renewable fuels, as the rate of depletion of non-
renewable energy rises at an alarming rate [1]. The utilization of fossil fuels presents a dual threat to society,
encompassing both escalating fuel demand and the exacerbation of climatic change, as non-renewable energy sources
wield significant influence over climate patterns, environmental stability, and ecological balance, while their continued
usage drives up fuel costs and contributes to climatic upheaval by releasing greenhouse gases [2]. On the other hand, in
the year 2023, the total amount of greenhouse gas (GHG) emissions, when expressed in terms of carbon dioxide
equivalent (CO₂eq), reached a value of 58.3 gigatons (GT) [3], and in the absence of alterations, the Earth's atmospheric
CO2 levels may potentially attain 550 parts per million (ppm) by 2050, following the trajectory of the "business as usual"
scenario [4]. Considering various alternatives for depleting sources of energy, biomass has been an essential component of
energy debates within the policy context, strongly desired by the European Union, which has been able to transform
environmental protection and cost-cutting measures into strategic implementation plans for development. The allure of
biomass energy lies in its roots – drawing upon the planet's inherent ability to regenerate organic matter. Unlike fossil
fuels, which rely on finite reservoirs, biomass presents a renewable source that continuously replenishes through natural
cycles [5].
Biomass energy, or Bioenergy, is the energy derived from organic materials ranging from agricultural residues and
forest byproducts to algae and municipal waste. Since photosynthesis locks atmospheric CO 2 into organic matter, which
when combusted re-releases the CO 2 back into the atmosphere, this implies that carbon is extracted during the plant's
growth stage and subsequently released during the process of energy conversion: Bioenergy is considered a low carbon
form of renewable energy, and a well management of biomass resources plays a crucial role in boosting the efficiency of
such renewable system [6]. In the year 2020, the global domestic biomass supply amounted to 57.5 exa-joules (EJ).
Notably, approximately 86% of this domestic supply originated from solid biomass sources, encompassing wood chips,
wood pellets, and traditional biomass sources. In 2020, 685 TWh of electricity was generated from biomass globally. Asia
accounted for 39% of all biopower generated globally with 255 TWh of production in 2019 followed by Europe at 35%.
Electricity only plants are designed to produce electricity only. In 2020, 5.3 EJ of biomass was used in electricity only
plants for power generation. [7].
Fossil resources are extracted in large quantities from a few concentrated deposits worldwide and are mainly utilized
for energy, chemicals, and construction. In contrast, bio-based materials are sourced from widespread agricultural and
forestry areas, necessitating decentralized management due to transportation costs. Biorefineries, centers for processing
biomass, are also structured in a decentralized manner. The bio-based value chain is intricate, including sectors like seed
production and agrochemicals. The energy sector is a significant consumer, using a considerable portion of forestry and
agricultural output. In essence, within the realm of bio-based value chains, the foremost significance lies in the food
sector, which consumes 84% of agricultural production, while the energy sector constitutes 14% of the consumption share.
Industrial utilization of agricultural biomass in domains beyond food and energy, however, constitutes a mere 2% [8].
Biomass stands as a renewable energy reservoir in plentiful supply on our planet, encompassing both woody biomass
and agricultural residue. This diverse resource is grouped into categories such as vegetable oil, sugar and starch,
lignocellulosic matter, and wet biomass. Through a range of distinct technologies like transesterification, gasification,
pyrolysis, anaerobic digestion, pelletization, hydrolysis, and fermentation, these distinct biomass types can be skillfully
transformed into a variety of valuable outputs including biodiesel, biogas, chemicals, electricity, heat, and hydrocarbons
[9]. Bioenergy's contribution to emission reductions, hinges upon a comprehensive grasp of emission releases and
sequestrations. This entails generating precise emission data from bioenergy systems, accounting for specific conditions,
timeframes, locations, and scales. A shift beyond conventional static evaluations is imperative, as each bioenergy system
necessitates tailored consideration of its unique attributes, context, and interconnections. Furthermore, comprehending the
dynamics of emission sequestration, emission fluctuation patterns, and atmospheric load constraints becomes pivotal.
These insights will guide the selection of bioenergy alternatives capable of meeting requisite emission standards,
reinforcing the pursuit of sustainable solutions [10].
 Figure 1- carbon cycle throughout the production and utilization of biomass (Tursi, 2019) [5]

2. Bioenergy Resources Assessment:

2.1. Biomass and biomass energy resources
Every organic substance deriving directly or indirectly from the photosynthesis process is considered biomass [11].
The most significant biomass sources (seen in Fig. 2) include sewage, algae, aquatic crops, agricultural and forestry
leftovers, animal residues (from livestock farms), and waste products from the wood-processing sector. Only if they
cannot be reused in later processing do municipal solid waste (MSW) and waste streams from human activities also fall
under the biomass category [5].

Figure 2- the most important biomass sources [5]

Consequently, biomass covers a wide range of resources, including agricultural crops, timber, marine plants, and other
types of conventional agriculture, forestry, and fisheries resources. It also includes pulp sludge, black liquor, alcohol
fermentation stillage, and other organic industrial waste, as well as municipal waste like paper and food scraps.
Nevertheless, care must be taken when using statistics data since some nations do not designate municipal garbage as
biomass [12].
An extended overview of the organic and inorganic phase composition of biomass was conducted by S.V. Vassilev et al.
(2012) [13], concluding that cellulose (Cel), hemicellulose (Hem), and lignin (Lig) are the three main structural organic
components of biomass. Major, minor, and accessory organic and inorganic compounds are associated with these matrices
and are represented by a variety of solid and fluid phases with varying contents and origins. From the same study, it was
demonstrated that:
1. Biomass composition, particularly the constituents of ash, varies significantly due to differences in moisture
content, ash yield, and the presence of diverse inorganic elements. These variations can be attributed to the
types of inorganic materials within different biomass sources.
2. The distinct chemical characteristics of various biomass groups, whether originating from plant and animal
products or mixtures of both, are considerable. This differentiation is influenced by the biomass's source and
origin, creating notable differences in chemical makeup.
3. Biomass primarily consists of elements like C, O, H, N, Ca, K, Si, Mg, Al, S, Fe, P, Cl, Na, Mn, and Ti.
Notably, biomass chemical composition differs from that of coal, with greater variations observed among
biomass samples. Biomass tends to be enriched in elements such as Mn, K, P, Cl, and Ca, but depleted in ash,
Al, C, Fe, N, S, Si, and Ti when compared to coal.
4. By examining correlations and associations among chemical attributes, significant trends emerged in natural
biomass systems. Five strong associations were identified: C-H, N-S-Cl, Si-Al-Fe-Na-Ti, Ca-Mg-Mn, and K-
P-S-Cl. These associations offer potential for preliminary classification, prediction, and indicator purposes
related to biomass.
T. Kalak (2023), conducted a study presenting an overview of the research done so far on the possibility of using
biomass waste as renewable energy [14], along with S.V. Vassilev study [13], the general classification of biomass is
shown in table 1. [13][14]. Chum et al. (2012) [12] worked on the special report on renewable energy sources, in this
context, the report included a study on biomass feedstock production and harvest, with a summary on the performance
characteristics of major biomass production systems, dedicated plants or primary residues across the world regions. The
biomass variety in species and composition, implies a huge variety in energy stored within every type and specie,
requiring diverse conversion technologies: only a fraction of the total aboveground biomass is used for biofuels, with the
rest being processed for animal feed or lignocellulosic residues [12].
Table 1- Types of biomasses for energy

Type of Biomass Species and Varieties

Wood and woody biomass Wood industrial waste, forest waste, branches, stems, chips, foliage,
lumps, pellets, briquettes, sawdust, bark, sawmill, and others from various
wood species

Herbaceous biomass Flowers and grasses (bamboo, brassica, timothy, alfalfa, miscanthus,
switchgrass, cane, arundo, bana, cynara, others); straws (sunflower, mint,
bean, barley, flax, oat, sesame, wheat, corn, rice, rape, rye, others); other
residues (husks, fruits, grains, vegetables, coir, pips, cakes, bagasse,
fodder, pits, hulls, pulps, kernels, seeds, shells, stalks, cobs, food, etc.)

Aquatic biomass Freshwater or marine algae, microalgae or macroalgae, kelp, lake weed,
seaweed, water hyacinth, etc.

Animal and human waste biomass Various manures, meat-bone meal, bones, etc.

Note that the Woody biomass is currently the most important renewable energy source in the world [15].
The huge variety of biomass sources can be used in many fields: heat, electricity (power), liquid biofuels and biobased
products (to be discussed later on) [20]. See figure 3.

Figure 3- Biomass sources classification for energy production [20]

2.2. Availability and Potentials of Biomass

Biomass is already a major contributor to world energy needs, and there is extent for improving this contribution in
both, developed and developing countries. However, the "fuel versus food" argument serves as a particularly poignant
example of the current and controversial nature of the availability of increased biomass for energy purposes [16]. The
collective yearly primary biomass production on Earth's surface is approximated at 1260 EJ/year, encompassing biomass
dedicated to food, fodder, fiber, and various industrial outputs totaling 219 EJ/year. Nevertheless, assessments considering
sustainability limits indicate an annual potential of 200–500 EJ/year, aligning with the current worldwide energy
consumption. Projections for 2050 suggest a bioenergy contribution spanning 100–300 EJ/year, amounting to roughly a
quarter to a third of the anticipated global energy composition [17]. According to the World Bioenergy Association, the
combined global resources of aquatic and terrestrial biomass are approximately 4 billion tons and 1.8 trillion tons,
respectively. This estimation indicates that the total biomass across the world has the capacity to play a role in generating
around 33,000 RJ (exa-joules) of energy. Remarkably, this amount exceeds the world's yearly energy consumption by over
80 times [18].
Biomass is hugely present in various spots on land and in the aquatic areas, in addition to the waste of human industrial
activities. Agriculture stands as a pivotal domain for enhancing future bioenergy potential. The global cultivation of
diverse crops presents a significant opportunity, enabling an increase in both food and fuel production through bioenergy
means. Following forestry and agriculture, another noteworthy sector is the conversion of energy from municipal and
industrial waste. In 2019, the energy generated from this source reached 2.59 EJ [7][14].
 The prospective energy contribution from biomass hinges heavily on the availability of land. Presently, the land
allocated for biofuel cultivation is a mere 0.025 billion hectares, constituting a mere 0.19% of the Earth's total land area of
13.2 billion hectares. In terms of agricultural land, this figure corresponds to 0.5-1.7% of the global agricultural expanse
[19]. The long-term viability of energy crops depends largely on land availability, which is shaped by factors including
food sector growth, access limitations due to water availability and environmental concerns. The choice of energy crops
also plays a crucial role in defining achievable biomass yields on the available land. Other factors affecting biomass
potential include the impact of biotechnology like genetically modified organisms, water availability, and the influence of
climate change on productivity [20].

Figure 4- Biomass supply potential, demand, and global energy models for 2050 primary energy demand [20]

Considering the wide array of available feedstocks, the literature suggests that the technical potential for biomass
energy could reach up to 1500 EJ/yr by 2050. However, when considering sustainability constraints, most biomass supply
scenarios indicate a more realistic annual potential of 200 to 500 EJ/yr (excluding aquatic biomass). Within this context,
forestry and agricultural residues, as well as other organic wastes such as municipal solid waste, could contribute around
50 to 150 EJ/year. The remaining energy output would be derived from sources like energy crops, surplus forest growth,
and improved agricultural productivity. See Figure 4 [20]. M. Kamran defined the energy density of biomass as the energy
contained in it [8]. Table 2 shows the storage density and the energy density of various biomass resources, noting that the
energy density increases by making pellets and briquettes for a specific biomass source.
Table 2- Density and energy density of different biomass types

Biomass type Energy density (GJ/m3) Density (kg/m3)

Bio-oil 20 1200
Torrefied pallets 15 800
Pellets 9.8-14 550-700
Briquets 6.4 350
Ground biomass 3.6 200
Baled biomass 2.8-4.7 160-255
 2.3. Biomass energy current status and future trends
The International Renewable Energy Agency (IRENA, 2022) has developed a report that outlines sustainable
developments in bioenergy [21], focusing on the role of bioenergy in decarbonizing power and end-use sectors in the
energy transitions. The report confirmed the fact that bioenergy is the highest contributor in the renewable energy
resources with 12% share, it can be used for power generation and end-use including heating, cooking and transportation.

Figure 5- Share of global bioenergy consumption by end-use (IRENA 2022) [21]

More than half of the overall bioenergy consumption was attributed to the inefficient and traditional utilization of solid
biomass like firewood, charcoal, crop residues, and animal dung. This practice prevailed among over 2.4 billion
individuals, primarily in developing areas of sub-Saharan Africa and South Asia. These regions face challenges of
restricted availability to cost-effective and dependable contemporary energy systems [21]. This data is approved by
RENEWABLES report (REN 22), with more specific details on the modern bioenergy used [23]. A fall of 8% in the
traditional use of bioenergy has happened since 2011, which coincides with 7% increase in the modern bioenergy use in
buildings between 2010 and 2020. Modern bioenergy for heating in buildings and industry provided around 14.7 EJ in
2020 (7.6% of the global energy use for heating), transport use amounted to 3.7 EJ (3.5% of transport energy needs),
bioenergy also provided 1.8 EJ to the global electricity supply (2.4% of the total) [23]. The contemporary application of
bioenergy pertains to the improved utilization of solid and gaseous biofuels in heating and power generation, as well as
the use of liquid biofuels and biomethane for transportation and various other purposes. In 2019, the advanced utilization
of bioenergy accounted for approximately 6% of the global final energy demand, surpassing both hydropower and other
modern renewable sources. The collective market value of modern solid and liquid bioenergy was estimated to be around
USD 79 billion in 2019, comprising USD 34 billion from bioethanol, USD 35 billion from biodiesel, and USD 10 billion
from wood pellets [22]. Bioenergy contributes 17% of the total final energy consumption in the 1.5°C Scenario by 2050.
All end consumers of bioenergy today would need to use more of it (see Figure 6). 25% of the world's total primary
energy source comes from biomass. This is 153 EJ of biomass, a threefold increase in comparison to the level of 2018
[21].
 Figure 6- Primary bioenergy supply in 2018 (left) and 2050 (right) in the 1.5°C Scenario (IRENA 2021) [21]

Biofuel commerce has grown internationally for many years. The top exporters of wood pellets during the past five
years have been Canada, the Russian Federation, the United States, and Vietnam. Biodiesel is the most widely traded
bioenergy in terms of energy value, making up the majority of all traded commodities for bioenergy in 2020. The main
destination is Europe, although other options include Japan and the Republic of Korea. a growing market. The top
exporters of biodiesel are Argentina, China, Indonesia, Malaysia, and the European Union imports. The leading exporter
of bioethanol is the United States, with significant importers include the Republic of Korea, Canada, Colombia, and India
[21]. See table 3 for information about the status of Bioenergy products in leading countries provided by Renewables
2022 [23].
Table 3- Status of Bioenergy products in leading countries (Renewables 2022) [23]

Bioenergy Product Status Leading Countries Energy Produced (year)

Ethanol Leading source of transport United States, Brazil, China, 2.3 EJ (2021)
biofuels India
Biodiesel Significant production growth, Indonesia, Brazil, United 1.5 EJ (2021)
widely distributed States, European Union
Hydro processed Vegetable Rapid growth in production United States, Europe, China, 9.5 billion liters
Oils (HVO) Netherlands
Sustainable Aviation Fuel Increasing focus, rapid Europe, United States, China 80 PJ (2021)
(SAF) production growth
Biomethane Used for transport mainly in United States, Europe 41 PJ (2021)
US and Europe

The World Bioenergy Association (WBO) provides data in the Global Bioenergy statistics report (2022), about
renewable electricity: 7 669 TWh of renewable electricity was produced globally, with hydropower as the largest
renewable electricity generating source with a share of 58%. Bioenergy was the fourth largest renewable electricity
generating source with production of 685 TWh in 2020, not that in increased from 162 TWh of electricity in 2000 [19].
Europe is the largest producer of biopower with an estimated generation of 304 TWh, accounting for 40% of all
bioelectricity generation globally [19]. See Figure 7.
 Figure 7- Renewable power generation in continents in 2019 [19]

In 2020, biogas, solid biomass and liquid biofuels supported over 3.53 million jobs globally (see Figure 8), a number
that could reach 13.7 million by 2050. Low-paid agricultural laborers make up a significant portion of the supply chain for
bioenergy in many developing nations. They may have difficult working conditions, and the majority of these jobs are
held by males [21].

Figure 8- Numbers of bioenergy jobs and share n total renewable energy jobs, 2012-2019 [21]
 Figure 9- Global Bioenergy trade in major markets in 2020 [21]

The International Energy Agency (IEA) reports on Biomass energy, on which rely most of IRENA and REN22’s data,
talks about the net zero emissions (NZE) plan for 2030, in which: the traditional use of biomass in rural areas partly
replaced by biogas digesters, bioethanol and solid biomass used in modern cookstoves, providing a source of clean
cooking for almost 1.2 billion people by 2030, and the total global bioenergy use will be 12% higher than that in 2022 (the
traditional use having falling to zero in the NZE scenario in 2030), see Figure 10 [24].

Figure 10- Bioenergy supply globally in the Net Zero Scenario, 2010-2030 [24]

3. Biomass for energy: biomass products

3.1. Biomass products
3.1.1. Biofuels
Any fuel made from organic materials, such as plants and their byproducts, agricultural crops, and byproducts, that
may effectively replace petroleum-derived gasoline is referred to as a biofuel [25]. Biofuels can be used either in their
pure form or as fuel additives, additionally, main biofuels are often separated into bioethanol and biodiesel [26]. Today,
approximately 80% of liquid biofuel is manufactured in bioethanol, and the rest is via biodiesel [27]. There are several
ways to make biofuels, including biological, chemical, and physical processes, and based on the feedstock used to produce
them, the liquid biofuels are broadly categorized into first, second, third and fourth generation biofuels [28]. Table 4
shows details about the four mentioned groups of biofuels [29].
Table 4- Biofuels generations' characteristics

Biofuels Feedstock Production Focus and Benefits Technological Aspects

Generation Method
First- Animal feed crops, Fermentation Production of fuel Use of fermentation
generation food products Distillation Conventional biofuels distillation, and
Transesterification Limited focus on non-fuel transesterification
waste
Second- Non-food feedstocks Various biorefinery Increased fuel recovery Use of membrane filtration
generation Lignocellulosic plants techniques Production of secondary Integration of biorefineries.
Agriculture residues Membrane filtration raw material Mesophilic and thermophilic
Forest residues Integration Reduced energy cost organisms.
Waste products Less waste Batch and continuous reactions
Economically feasible
Third- Microalgae Transesterification Higher biofuels yield Use of microalgae,
generation Hydrotreatment Derived from microalgae transesterification,
Advanced biofuels hydrotreatment.
Reduced water pollution Research progress
Waste load Feasible resources: microalgae,
animal oils, etc.
Fourth- Genetically modified Photobiological solar Use of GM algae GM algae biomass, genome
generation algae fuels Improved photosynthetic editing tools
Photobiological solar Electro-fuels efficiency Photobiological solar fuels,
fuels Genetic modification Increased light penetration electro-fuels
Electro-fuels Genetically modified algae Genome editing tools: ZFN,
TALEN, CRISPR/Cas9

Biofuels are also be classified into two types: solid, liquid and gaseous biofuels [29], see Table 5
TYPE OF DESCRIPTION MAIN USES
BIOFUEL
SOLID BIOFUELS These biofuels are produced from charcoal, fuelwood, Heat production, energy and electricity
wood pellets, wood residue, animal waste and other generation
renewable industrial waste
LIQUID  Bioethanol: produced from agricultural crops  Fuel for gasoline engines, blending in
BIOFUELS or cellulosic materials through fermentation gasoline
 Biodiesel: derived from vegetable oils or
animal fats via transesterification process  Diesel engine fuel, blending with diesel
 Bio-oil: produced from biomass pyrolysis or fuel
liquefaction processes  Can be refined for uses as liquid fuel or
heating
GASEOUS  Biogas: produced from organic matter  Electricity and heat generation
BIOFUELS decomposition in anaerobic conditions
 Biohydrogen: generated through biological  Potential fuel for fuel cells and
processes using microorganisms or algae combustion
 Biosyngas: produced through gasification of
biomass materials  Combustion for electricity or heat
generation

3.1.2. Biopower
Biopower is the heat or electricity produced from biomass: biomass power where heat or electricity are produced from
direct combustion of biomass, biogas power where heat or electricity are generated from the combustion or gasification of
biogas produced through anaerobic digestion. Generally, bioelectricity is that generated by burning biomass to produce
steam [33]. Utilizing agricultural biomass feedstocks for pyrolysis represents a sustainable strategy that reduces
greenhouse gas emissions while also producing biopower. In the pyrolysis process, agricultural biomass is subjected to
heat in an oxygen-free environment, leading to the breakdown into bio-oil, biogas, and biochar. These products have the
potential to serve as fuel sources for generating power [34].
Biomass can be converted into two main types of energy carriers: electrical/heat energy and transportation fuels [35].
Energy usage involves employing biomass to generate electricity and heat, as well as converting biomass into secondary
products like biofuels for transportation purposes. In the context of bioenergy, the energy content of the fuel is regarded as
primary energy. Heat that is produced as a result is referred to as derived heat when it is generated within power plants,
including combined heat and power as well as heat-only plants. This heat is subsequently transferred through district
heating networks for consumption in various end sectors [7].

Figure 11- Various technologies developed to upgrade a diverse portfolio of biomass feedstocks into bioenergy [36]

Conversion processes:
Biomass combustion is not the best strategy economically due to environmental damage and incomplete energy
recovery [30]. Biomass can be converted into solid, liquid, and gaseous forms, offering efficiency and environmental
friendliness for heat, power, and transport fuels. This conversion occurs through two main routes: thermochemical
methods utilize the entire biomass with heat and controlled oxygen to generate diverse energy forms, while biochemical
methods employ enzymes, bacteria, or other organisms to convert biomass into liquid fuels like drop-in-biofuels. Over
time, biomass-derived fuel synthesis has advanced from first-generation biofuels, derived from food crops, to fourth-
generation biofuels involving genetically bioengineered systems. This progress has led to the production of various
biomass-based fuels, chemicals, and organic compounds through distinct biomass-to-liquid routes, available on a global
scale [31].
 Figure 12- Bioenergy production [5]

There are two main routes for converting biomass into biofuels: thermochemical and biochemical. Thermochemical
processes include gasification, combustion, pyrolysis, and enzymatic hydrolysis routes. Gasification, combustion, and
pyrolysis are classified as high-temperature processes, while enzymatic hydrolysis operates at a relatively lower
temperature. Biochemical conversion involves fermentation and anaerobic digestion processes. Thermochemical
conversion is more researched and understood than the biochemical counterpart, but there is scope for further research in
the biochemical route [32].

Figure 13- Thermochemical and Biochemical conversion processes for Biomass [32]

The need for new energy sources has arisen from increasing energy consumption, dwindling reserves of fossil fuels,
and the pressing requirement to lower carbon dioxide emissions. The efficient energy conversion process of biomass can
fulfill energy needs: thermochemical and biochemical processes generally accomplish the conversion of biomass into
biofuels [37]. For thermochemical processes, three main ways are used two lesser-used options [38], see table 5.
Table 5- Thermo-chemical conversion processes [38]

PROCESS DESCRIPTION PURPOSE/ END PRODUCTS

COMBUSTION Burning biomass in air to convert its Generate heat, mechanical power, or
chemical energy into heat, power or electricity for various applications.
electricity using various equipment.
GASIFICATION Partial oxidation of biomass at high Direct combustion, gas engines, gas
temperature to produce a combustible gas turbines, or chemical production
mixture used for engines, turbines, or (methanol…)
chemicals.
 PYROLYSIS Biomass conversion through heating in Bio-oil can be used in engines, turbines,
the absence of air to produce liquid (bio- and refineries; challenges in thermal
oil), solid and gaseous fractions. stability and corrosivity.

OTHER PROCESSES Hydrothermal upgrading (HTU) converts HTU explores wet biomass conversion,
wet biomass at high pressure to partly while liquefaction is complex and less
oxygenated hydrocarbons. Liquefaction favored due to cost and complexity.
transforms biomass into stable liquid
hydrocarbons using low temperature and
high hydrogen pressures.

Biochemical conversion of biomass involves use of bacteria, microorganisms and enzymes to breakdown biomass into
gaseous or liquid fuels [39]. Two primary methods are employed: fermentation and aerobic digestion (AD), along with a
less commonly utilized process involving mechanical extraction or chemical conversion [38], see table 6.
PROCESS DESCRIPTION PURPOSE/ END PRODUCTS
FERMENTATION Enzymatic conversion of starch or sugars Commercially used for large-scale
in biomass to ethanol by yeast. Applied ethanol production from crops. Residue
to sugar and starch crops. can be used as cattle-feed or fuel.
ANAEROBIC DIGESTION Conversion of organic material to biogas Proven technology for treating organic
(methane and CO2) by bacteria in an waste. Biogas can be used in engines and
anaerobic environment. Used for high- turbines, or upgraded to natural gas
moisture organic wastes. quality. Can produce electricity.
MECHANICAL EXTRACTION Mechanical process to extract oil from Extract oil from seeds like rapeseed,
biomass seeds, yielding oil and solid producing bio-diesel and solid cake. Used
residue. The oil can be further processed as supplementary transport fuel.
for bio-oil.

4. Environmental Impact of Bioenergy

Bioenergy stands as a distinctive form of renewable electricity, diverging from solar, wind and hydropower in that its
power generation releases greenhouse gases and pollutants into the atmosphere. Nonetheless, owing that to biomass
renewable characteristics, numerous individuals consider it as carbon-neutral reservoir of electrical energy [40]. Biofuels,
in comparison to petroleum fuels derived from crude oil, tend to result in less pollution when burned. However, the
environmental impact of biofuels production and utilization should not be overlooked. Biofuels are often deemed
potentially carbon-neutral because the plants used in their production absorb carbon dioxide (CO2) as they grow. This
CO2 absorption can offset the emissions generated during the production and combustion of biofuels [41]. Utilizing
biomass energy can be a useful tool in putting carbon reduction measures into practice. While urbanization and economic
expansion were noted as elements that have a detrimental influence on the environment, trade openness was shown to
have a favorable effect on environmental quality. Additionally, switching to alternative biomass consumption patterns has
additional benefits by reducing the impact of economic development on environmental sustainability. The top countries
for biomass consumption have put in place biomass laws with an emphasis on lowering air pollution, but environmental
harm brought on by biomass use has been neglected. Therefore, regulating and speeding the switch from traditional to
modern biomass might enhance the green impacts of biomass use, therefore slowing the degradation of the environment
[42]. In comparison to their bio-based counterparts, conventional electricity and fuels continue to be more affordable,
however biomass has significant environmental benefits given that it is renewable, makes use of growing amounts of
waste, and significantly lowers greenhouse gas emissions, helping to combat climate change and global warming [5].
Biomass contains nitrogen and several essential nutrients other than carbon, efforts to intensively cultivate biomass has
other roles than carbon capture. Horticulture’s contribution to the global nitrogen cycles is associated with many
deleterious environmental consequences, where NO 2 has greater global warming potential than a molecule of CO 2:
intensive agriculture, including horticulture, contributes to nitrogen pollution through the release of reactive nitrogen
compounds into the environment [43]. Additionally, horticulture is a very water-intensive activity, needing several orders
of magnitude more water per hectare than is required for domestic and industrial reasons [44]. The removal of biomass
from land and water for energy generation programs worsens floods, nitrogen loss, and soil and water deterioration.
Wildlife and the natural biota are also impacted. Numerous individuals are not aware of these or other environmental risks
associated with the production of biomass since their focus is on how biomass energy is supposedly "carbon neutral" [43].
The impact of thermal conversions is not the only topic to be assessed, fermentation has also its environmental impacts:
‘‘if alcohol is a ‘clean’ fuel the process of making it is very dirty” [45].
In conclusion, as IRENA, IEA bioenergy and FAO (2017) stated, sustainability in bioenergy is a difficult subject. In
theory, using bioenergy can have a number of advantages, such as reducing GHG emissions by switching to it in place of
fossil fuels for transportation, manufacturing, heating, and power generation. Additionally, it can result in socioeconomic
and environmental advantages including employment development, increased health through clean cooking, and land
restoration. These advantages, however, may only be realized in certain situations. Due to their close connections with
several key sectors, including agriculture, forestry, rural development, and waste management, bioenergy supply chains
and use might have detrimental environmental, social, or economic effects if they are not properly managed. Assessing the
positive and negative impacts on sustainability should be based on specific locations and other circumstances that
characterize the management of feedstock production [21].

Figure 14- potential aspects related to bioenergy sustainability, IRENA (2022) [21]

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https://www.bioenergyconsult.com/biochemical-conversion-technologies/
[40]: Environmental Impacts of biomass | EnergySage. (2019, December 24). https://www.energysage.com/about-
clean-energy/biomass/environmental-impacts-biomass/
[41]: Environmental Impacts of biomass | EnergySage. (2019, December 24). https://www.energysage.com/about-
clean-energy/biomass/environmental-impacts-biomass/
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sustainability? An SDG perspective for top five biomass consuming countries. Biomass and Bioenergy, 149, 106076.
https://doi.org/10.1016/j.biombioe.2021.106076
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