Project Report On

“ BIOMASS ENERGY ”
A seminar report submitted in the partial fulfilment of the requirements for the award of the degree
of Diploma in Engineering
In
Electrical engineering

Submitted by
Rashmiranjan Pradhan : L230400020
Rudraprasad Behera : L230400020
Smruti Ranjan Behera : L230400020
Suryamani Rout : L230400020
Suryakanta Maharana : L230400020

Under Guidance of
Er. Purna Chandra Sahoo

Department of Electrical Engineering

Gurukrupa technical school

Narasinghpur , cuttack

1
 CERTIFICATE

This is to certify that , the is entitled “ BIOMASS ENERGY ”

submitted by Rashmiranjan prahan, Rudraprasad Behera, Smruti
Ranjan Behera, Suryamani Rout, Suryakanta Maharana in partial
fulfilment of the requirements for the award of Diploma in Electrical
Engineering, at GURUKRUPA TECHNICAL SCHOOL, NARASINGHPUR,
CUTTACK in an authentic work carried out by them under my supervision
and guidance.

Principal Guide – Er. PURNA CHANDRA

SAHOO
GTS Narasinghpur Dept. of ELCT ENGG
GTS Narasinghpur

Mrs. SUSHREE SANGITA DASH

Head of the Department
Detp. of ELCT ENGG
GTS Narasinghpur

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 ACKNOWLEDGEMENTS

I wish to express my profound and sincere gratitude to Er. PURNA

CHANDRA SAHOO, Lecture in Electrical Engineering, GURUKRUPA
TECHNICAL SCHOOL, Narasinghpur, Cuttack, for guiding us into the
intricacies of this project non-chalanty.

I thank SUSHREE SANGITA DASH, Head of the Dept. of Electrical

Engineering, GURUKRUPA TECHNICAL SCHOOL, Narasinghpur,
Cuttack, for extending their support during the course of this
investigation.

Rashmiranjan Pradhan
L230400020
Rudraprasad Behera
L230400020
Smruti Ranjan Behera
L230400020
Suryamani Rout
L230400020
Suryakanta Maharana
L230400020

3
 ABSTRACT

This study investigates biomass energy applications and

development in Uganda. Traditional biomass dominates Uganda's energy
mix with 89% of overall primary energy consumption. Uganda must
reduce traditional biomass energy consumption if it is to reinforce its
sustainable development goals. It seeks to assess bioenergy applications;
it also analyses drivers and barriers of biomass consumption.

The findings indicate an in-built use of traditional biomass because

of the drivers that outweigh the constraints of its use. Suggested policy
measures to transition to modern biomass energy consumption are made.

This study provides critical review of bioenergy application and

development in the Ugandan setting. This is a landmark in informing the
economic planner on the right policy direction of diversifying energy use.

4
 Content

Biomass Energy
20

5
 Biomass Energy

In the context of energy production, biomass is matter from recently living (but now
dead) organisms which is used for bioenergy production. Examples include wood, wood
residues, energy crops, agricultural residues including straw, and organic waste from industry
and households.[1] Wood and wood residues is the largest biomass energy source today. Wood
can be used as a fuel directly or processed into pellet fuel or other forms of fuels. Other plants
can also be used as fuel, for instance maize, switchgrass, miscanthus and bamboo.[2] The
main waste feedstocks are wood waste, agricultural waste, municipal solid waste,
and manufacturing waste. Upgrading raw biomass to higher grade fuels can be achieved by
different methods, broadly classified as thermal, chemical, or biochemical.

The climate impact of bioenergy varies considerably depending on where biomass

feedstocks come from and how they are grown.[3] For example, burning wood for energy
releases carbon dioxide. Those emissions can be significantly offset if the trees that were
harvested are replaced by new trees in a well-managed forest, as the new trees will remove
carbon dioxide from the air as they grow. [4] However, the farming of biomass feedstocks
can reduce biodiversity, degrade soils and take land out of food production. [5] It may also
consume water for irrigation and fertilisers.[6][7]

Terminology
Biomass (in the context of energy generation) is matter from recently living (but now
dead) organisms which is used for bioenergy production. There are variations in how such
biomass for energy is defined, e.g. only from plants, [8] or from plants and algae, [9] or from
plants and animals.[10] The vast majority of biomass used for bioenergy does come from
plants. Bioenergy is a type of renewable energy with potential to assist with climate change
mitigation.[11]

Some people use the terms biomass and biofuel interchangeably, but it is now more
common to consider biofuel to be a liquid or gaseous fuel used for transportation, as defined
by government authorities in the US and EU.[a][b] From that perspective, biofuel is a subset of
biomass.

The European Union's Joint Research Centre defines solid biofuel as raw or processed
organic matter of biological origin used for energy, such as firewood, wood chips, and wood
pellets.[12]: 20–21

Types and uses

Different types of biomass are used for different purposes:

 Primary biomass sources that are appropriate for heat or electricity generation
but not for transport include: wood, wood residues, wood pellets, agricultural
residues, organic waste.
 Biomass that is processed into transport fuels can come from corn, sugar cane,
and soy.

6
 Biomass is categorized either as biomass harvested directly for energy (primary
biomass), or as residues and waste: (secondary biomass).[13][14]

Biomass harvested directly for energy

The main biomass types harvested directly for energy is wood, some food crops and
all perennial energy crops. One third of the global forest area of 4 billion hectares is used
for wood production or other commercial purposes,[15] and forests provide 85% of all biomass
used for energy globally.[16]: 3 In the EU, forests provide 60% of all biomass used for energy,
[17]
with wood residues and waste being the largest source.[18]

Woody biomass used for energy often consists of trees and bushes harvested
for traditional cooking and heating purposes, particularly in developing countries, with 25 EJ
per year used globally for these purposes. [19] This practice is highly polluting. The World
Health Organization (WHO) estimates that cooking-related pollution causes 3.8 million
annual deaths.[20] The United Nations Sustainable Development Goal 7 aims for the traditional
use of biomass for cooking to be phased out by 2030. [21] Short-rotation coppices[c] and short-
rotation forests[d] are also harvested directly for energy, providing 4 EJ of energy, [19] and are
considered sustainable. The potential for these crops and perennial energy crops to provide at
least 25 EJ annually by 2050 is estimated.[19][e]

Food crops harvested for energy include sugar-producing crops (such

as sugarcane), starch-producing crops (such as maize), and oil-producing crops (such
as rapeseed).[22] Sugarcane is a perennial crop, while corn and rapeseed are annual crops.
Sugar- and starch-producing crops are used to make bioethanol, and oil-producing crops are
used to make biodiesel. The United States is the largest producer of bioethanol, while the
European Union is the largest producer of biodiesel. [23] The global production of bioethanol
and biodiesel provides 2.2 and 1.5 EJ of energy per year, respectively. [24] Biofuel made from
food crops harvested for energy is also known as "first-generation" or "traditional" biofuel
and has relatively low emission savings.

The IPCC estimates that between 0.32 and 1.4 billion hectares of marginal land are
suitable for bioenergy worldwide.[f]

Biomass in the form of residues and waste

Residues and waste are by-products from biological material harvested mainly for
non-energy purposes. The most important by-products are wood residues, agricultural
residues and municipal/industrial waste:

Wood residues are by-products from forestry operations or from the wood
processing industry. Had the residues not been collected and used for bioenergy, they would
have decayed (and therefore produced emissions) [g] on the forest floor or in landfills, or been
burnt (and produced emissions) at the side of the road in forests or outside wood processing
facilities.[25]

7
 Sawdust is residue from the wood processing industry.
The by-products from forestry operations are called logging residues or forest
residues, and consist of tree tops, branches, stumps, damaged or dying or dead trees, irregular
or bent stem sections, thinnings (small trees that are cleared away in order to help the bigger
trees grow large), and trees removed to reduce wildfire risk. [h] The extraction level of logging
residues differ from region to region,[i][j] but there is an increasing interest in using this
feedstock,[k] since the sustainable potential is large (15 EJ annually). [l] 68% of the total forest
biomass in the EU consists of wood stems, and 32% consists of stumps, branches and tops.[26]

The by-products from the wood processing industry are called wood processing
residues and consist of cut offs, shavings, sawdust, bark, and black liquor. [27] Wood processing
residues have a total energy content of 5.5 EJ annually. [28] Wood pellets are mainly made from
wood processing residues,[m] and have a total energy content of 0.7 EJ. [n] Wood chips are made
from a combination of feedstocks,[29] and have a total energy content of 0.8 EJ.[o]

The energy content in agricultural residues used for energy is approximately 2 EJ.
However, agricultural residues has a large untapped potential. The energy content in the
[p]

global production of agricultural residues has been estimated to 78 EJ annually, with the
largest share from straw (51 EJ). [q] Others have estimated between 18 and 82 EJ. [r] The use of
agricultural residues and waste that is both sustainable and economically feasible [13]: 9 is
expected to increase to between 37 and 66 EJ in 2030.[s]

Municipal waste produced 1.4 EJ and industrial waste 1.1 EJ. [30] Wood waste from
cities and industry also produced 1.1 EJ. [28] The sustainable potential for wood waste has been
estimated to 2–10 EJ.[31] IEA recommends a dramatic increase in waste utilization to 45 EJ
annually in 2050.[32]

Biomass conversion
Raw biomass can be upgraded into better and more practical fuel simply by
compacting it (e.g. wood pellets), or by different conversions broadly classified as thermal,
chemical, and biochemical.[33] Biomass conversion reduces the transport costs as it is cheaper
to transport high density commodities.[13]: 53

Thermal conversion
Thermal upgrading produces solid, liquid or gaseous fuels, with heat as the dominant
conversion driver. The basic alternatives are torrefaction, pyrolysis, and gasification, these
are separated principally by how far the chemical reactions involved are allowed to proceed.
The advancement of the chemical reactions is mainly controlled by how much oxygen is
available, and the conversion temperature.

Torrefaction is a mild form of pyrolysis where organic materials are heated to 400–
600 °F (200–300 °C) in a no–to–low oxygen environment.[34][35] The heating process removes

8
(via gasification) the parts of the biomass that has the lowest energy content, while the parts
with the highest energy content remain. That is, approximately 30% of the biomass is
converted to gas during the torrefaction process, while 70% remains, usually in the form of
compacted pellets or briquettes. This solid product is water resistant, easy to grind, non-
corrosive, and it contains approximately 85% of the original biomass energy. [36] Basically the
mass part has shrunk more than the energy part, and the consequence is that the calorific
value of torrefied biomass increases significantly, to the extent that it can compete with coals
used for electricity generation (steam/thermal coals). The energy density of the most common
steam coals today is 22–26 GJ/t.[37] There are other less common, more experimental or
proprietary thermal processes that may offer benefits, such as hydrothermal upgrading
(sometimes called "wet" torrefaction.) [t] The hydrothermal upgrade path can be used for both
low and high moisture content biomass, e.g. aqueous slurries.[38]

Pyrolysis entails heating organic materials to 800–900 °F (400–500 °C) in the near
complete absence of oxygen. Biomass pyrolysis produces fuels such as bio-oil, charcoal,
methane, and hydrogen. Hydrotreating is used to process bio-oil (produced by fast pyrolysis)
with hydrogen under elevated temperatures and pressures in the presence of a catalyst to
produce renewable diesel, renewable gasoline, and renewable jet fuel.[39]

Gasification entails heating organic materials to 1,400–1700 °F (800–900 °C) with

injections of controlled amounts of oxygen and/or steam into the vessel to produce a carbon
monoxide and hydrogen rich gas called synthesis gas or syngas. Syngas can be used as a fuel
for diesel engines, for heating, and for generating electricity in gas turbines. It can also be
treated to separate the hydrogen from the gas, and the hydrogen can be burned or used in fuel
cells. The syngas can be further processed to produce liquid fuels using the Fischer-Tropsch
synthesis process.[33][40]

Chemical conversion
A range of chemical processes may be used to convert biomass into other forms, such
as to produce a fuel that is more practical to store, transport and use, or to exploit some
property of the process itself. Many of these processes are based in large part on similar coal-
based processes, such as the Fischer-Tropsch synthesis.[41] A chemical conversion process
known as transesterification is used for converting vegetable oils, animal fats, and greases
into fatty acid methyl esters (FAME), which are used to produce biodiesel.[33]

Biochemical conversion
Biochemical processes have developed in nature to break down the molecules of
which biomass is composed, and many of these can be harnessed. In most cases,
microorganisms are used to perform the conversion. The processes are called anaerobic
digestion, fermentation, and composting.[42]

Fermentation converts biomass into bioethanol, and anaerobic digestion converts

biomass into renewable natural gas (biogas). Bioethanol is used as a vehicle fuel. Renewable
natural gas—also called biogas or biomethane—is produced in anaerobic digesters at sewage
treatment plants and at dairy and livestock operations. It also forms in and may be captured
from solid waste landfills. Properly treated renewable natural gas has the same uses as fossil
fuel natural gas.[33]

Climate impacts
9
 The climate impact of bioenergy varies considerably depending on where biomass
feedstocks come from and how they are grown.[43] For example, burning wood for energy
releases carbon dioxide; those emissions can be significantly offset if the trees that were
harvested are replaced by new trees in a well-managed forest, as the new trees will absorb
carbon dioxide from the air as they grow.[44] However, the establishment and cultivation of
bioenergy crops can displace natural ecosystems, degrade soils, and consume water resources
and synthetic fertilisers.[6][7]

Approximately one-third of all wood used for traditional heating and cooking in
tropical areas is harvested unsustainably.[45] Bioenergy feedstocks typically require significant
amounts of energy to harvest, dry, and transport; the energy usage for these processes may
emit greenhouse gases. In some cases, the impacts of land-use change, cultivation, and
processing can result in higher overall carbon emissions for bioenergy compared to using
fossil fuels.[7][46]

Use of farmland for growing biomass can result in less land being available for
growing food. In the United States, around 10% of motor gasoline has been replaced by corn-
based ethanol, which requires a significant proportion of the harvest. [47][48] In Malaysia and
Indonesia, clearing forests to produce palm oil for biodiesel has led to serious social and
environmental effects, as these forests are critical carbon sinks and habitats for diverse
species.[49][50] Since photosynthesis captures only a small fraction of the energy in sunlight,
producing a given amount of bioenergy requires a large amount of land compared to other
renewable energy sources.[51]
Short-term vs long-term climate benefits
Regarding the issue of climate consequences for modern bioenergy, IPCC states:
"Life-cycle GHG emissions of modern bioenergy alternatives are usually lower than those
for fossil fuels."[52] Consequently, most of IPCC's GHG mitigation pathways include
substantial deployment of bioenergy technologies.[53]

Some research groups state that even if the European and North American forest
carbon stock is increasing, it simply takes too long for harvested trees to grow back.
Bioenergy from sources with high payback and parity times take a long time to have an
impact on climate change mitigation. They therefore suggest that the EU should adjust its
sustainability criteria so that only renewable energy with carbon payback times of less than
10 years is defined as sustainable,[u] for instance wind, solar, biomass from wood residues and
tree thinnings that would otherwise be burnt or decompose relatively fast, and biomass from
short rotation coppicing (SRC).[54]

The IPCC states: "While individual stands in a forest may be either sources or sinks,
the forest carbon balance is determined by the sum of the net balance of all stands." [55] IPCC
also state that the only universally applicable approach to carbon accounting is the one that
accounts for both carbon emissions and carbon removals (absorption) for managed lands (e.g.
forest landscapes.)[56]: 2.67 When the total is calculated, natural disturbances like fires and insect
infestations are subtracted, and what remains is the human influence.[v]

IEA Bioenergy state that an exclusive focus on the short-term make it harder to
achieve efficient carbon mitigation in the long term, and compare investments in new
bioenergy technologies with investments in other renewable energy technologies that only
provide emission reductions after 2030, for instance the scaling-up of battery manufacturing
or the development of rail infrastructure. [w] Forest carbon emission avoidance strategies give a

10
short-term mitigation benefit, but the long-term benefits from sustainable forestry activities
provide ongoing forest product and energy resources.[55]

Most of IPCC's GHG mitigation pathways include substantial deployment of

bioenergy technologies.[53] Limited or no bioenergy pathways leads to increased climate
change or shifting bioenergy's mitigation load to other sectors. [x] In addition, mitigation cost
increases.[y]

Carbon accounting system boundaries

Carbon positive scenarios are likely to be net emitters of CO 2, carbon negative
projects are net absorbers of CO 2, while carbon neutral projects balance emissions and
absorption equally.[57]

It is common to include alternative scenarios (also called "reference scenarios" or

"counterfactuals") for comparison.[12]: 83 The alternative scenarios range from scenarios with
only modest changes compared to the existing project, all the way to radically different ones
(i.e. forest protection or "no-bioenergy" counterfactuals.) Generally, the difference between
scenarios is seen as the actual carbon mitigation potential of the scenarios.[12]: 100

Alternative system boundaries for assessing

climate effects of forest-based bioenergy. Option 1 (black) considers only the stack
emissions; Option 2 (green) considers only the forest carbon stock; Option 3 (blue) considers
the bioenergy supply chain; Option 4 (red) covers the whole bioeconomy, including wood
products in addition to biomass.[27]
In addition to the choice of alternative scenario, other choices has to be made as well.
The so-called "system boundaries" determine which carbon emissions/absorptions that will be
included in the actual calculation, and which that will be excluded. System boundaries
include temporal, spatial, efficiency-related and economic boundaries.[27]

For example, the actual carbon intensity of bioenergy varies with biomass production
techniques and transportation lengths.

Temporal system boundaries

The temporal boundaries define when to start and end carbon counting. Sometimes
"early" events are included in the calculation, for instance carbon absorption going on in the
forest before the initial harvest. Sometimes "late" events are included as well, for instance
emissions caused by end-of-life activities for the infrastructure involved, e.g. demolition of
factories. Since the emission and absorption of carbon related to a project or scenario changes
with time, the net carbon emission can either be presented as time-dependent (for instance a
curve which moves along a time axis), or as a static value; this shows average emissions
calculated over a defined time period.

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 The time-dependent net emission curve will typically show high emissions at the
beginning (if the counting starts when the biomass is harvested.) Alternatively, the starting
point can be moved back to the planting event; in this case the curve can potentially move
below zero (into carbon negative territory) if there is no carbon debt from land use change to
pay back, and in addition more and more carbon is absorbed by the planted trees. The
emission curve then spikes upward at harvest. The harvested carbon is then being distributed
into other carbon pools, and the curve moves in tandem with the amount of carbon that is
moved into these new pools (Y axis), and the time it takes for the carbon to move out of the
pools and return to the forest via the atmosphere (X axis). As described above, the carbon
payback time is the time it takes for the harvested carbon to be returned to the forest, and the
carbon parity time is the time it takes for the carbon stored in two competing scenarios to
reach the same level.[z]

The static carbon emission value is produced by calculating the average annual net
emission for a specific time period. The specific time period can be the expected lifetime of
the infrastructure involved (typical for life cycle assessments; LCA's), policy relevant time
horizons inspired by the Paris agreement (for instance remaining time until 2030, 2050 or
2100),[58] time spans based on different global warming potentials (GWP; typically 20 or 100
years),[aa] or other time spans. In the EU, a time span of 20 years is used when quantifying the
net carbon effects of a land use change.[ab] Generally in legislation, the static number approach
is preferred over the dynamic, time-dependent curve approach. The number is expressed as a
so-called "emission factor" (net emission per produced energy unit, for instance kg CO 2e per
GJ), or even simpler as an average greenhouse gas savings percentage for specific bioenergy
pathways.[ac] The EU's published greenhouse gas savings percentages for specific bioenergy
pathways used in the Renewable Energy Directive (RED) and other legal documents are
based on life cycle assessments (LCA's).[ad][ae]

Spatial system boundaries

The spatial boundaries define "geographical" borders for carbon emission/absorption
calculations. The two most common spatial boundaries for CO 2 absorption and emission in
forests are 1.) along the edges of a particular forest stand and 2.) along the edges of a whole
forest landscape, which include many forest stands of increasing age (the forest stands are
harvested and replanted, one after the other, over as many years as there are stands.) A third
option is the so-called increasing stand level carbon accounting method. The researcher has to
decide whether to focus on the individual stand, an increasing number of stands, or the whole
forest landscape. The IPCC recommends landscape-level carbon accounting.

Further, the researcher has to decide whether emissions from direct/indirect land use
change should be included in the calculation. Most researchers include emissions from direct
land use change, for instance the emissions caused by cutting down a forest in order to start
some agricultural project there instead. The inclusion of indirect land use change effects is
more controversial, as they are difficult to quantify accurately. [af][ag] Other choices involve
defining the likely spatial boundaries of forests in the future.

Efficiency-related system boundaries

The efficiency-related boundaries define a range of fuel substitution efficiencies for
different biomass-combustion pathways. Different supply chains emit different amounts of
carbon per supplied energy unit, and different combustion facilities convert the chemical
energy stored in different fuels to heat or electrical energy with different efficiencies. The
researcher has to know about this and choose a realistic efficiency range for the different

12
biomass-combustion paths under consideration. The chosen efficiencies are used to calculate
so-called "displacement factors" – single numbers that shows how efficient fossil carbon is
substituted by biogenic carbon.[59][27] If for instance 10 tonnes of carbon are combusted with an
efficiency half that of a modern coal plant, only 5 tonnes of coal would actually be counted as
displaced (displacement factor 0.5).

Generally, fuel burned in inefficient (old or small) combustion facilities gets assigned
lower displacement factors than fuel burned in efficient (new or large) facilities, since more
fuel has to be burned (and therefore more CO 2 released) in order to produce the same amount
of energy.[27]

The displacement factor varies with the carbon intensity of both the biomass fuel and
the displaced fossil fuel. If or when bioenergy can achieve negative emissions (e.g. from
afforestation, energy grass plantations and/or bioenergy with carbon capture and
storage (BECCS),[32] or if fossil fuel energy sources with higher emissions in the supply chain
start to come online (e.g. because of fracking, or increased use of shale gas), the displacement
factor will start to rise. On the other hand, if or when new baseload energy sources with lower
emissions than fossil fuels start to come online, the displacement factor will start to drop.
Whether a displacement factor change is included in the calculation or not, depends on
whether or not it is expected to take place within the time period covered by the relevant
scenario's temporal system boundaries.[ah]

Economic system boundaries

The economic boundaries define which market effects to include in the calculation, if
any. Changed market conditions can lead to small or large changes in carbon emissions and
absorptions from supply chains and forests,[27] for instance changes in forest area as a response
to changes in demand. Macroeconomic events/policy changes can have impacts on forest
carbon stock.[ai] Like with indirect land use changes, economic changes can be difficult to
quantify however, so some researchers prefer to leave them out of the calculation.[aj]

System boundary impacts

The chosen system boundaries are very important for the calculated results. [27] Shorter
payback/parity times are calculated when fossil carbon intensity, forest growth rate and
biomass conversion efficiency increases, or when the initial forest carbon stock and/or
harvest level decreases.[60] Shorter payback/parity times are also calculated when the
researcher choose landscape level over stand level carbon accounting (if carbon accounting
starts at the harvest rather than at the planting event.) Conversely, longer payback/parity
times are calculated when carbon intensity, growth rate and conversion efficiency decreases,
or when the initial carbon stock and/or harvest level increases, or the researcher choose stand
level over landscape level carbon accounting.[ak]

Critics argue that unrealistic system boundary choices are made, [al] or that narrow
system boundaries lead to misleading conclusions. [27] Others argue that the wide range of
results shows that there is too much leeway available and that the calculations therefore are
useless for policy development.[am] EU's Join Research Center agrees that different
methodologies produce different results,[an] but also argue that this is to be expected, since
different researchers consciously or unconsciously choose different alternative
scenarios/methodologies as a result of their ethical ideals regarding man's optimal
relationship with nature. The ethical core of the sustainability debate should be made explicit
by researchers, rather than hidden away.[ao]

13
Comparisons of GHG emissions at the point of combustion
GHG emissions per produced energy unit at the point of combustion depend on
moisture content in the fuel, chemical differences between fuels and conversion efficiencies.
For example, raw biomass can have higher moisture content compared to some common coal
types. When this is the case, more of the wood's inherent energy must be spent solely on
evaporating moisture, compared to the drier coal, which means that the amount of
CO2 emitted per unit of produced heat will be higher.[61]

Many biomass-only combustion facilities are relatively small and inefficient,

compared to the typically much larger coal plants. Further, raw biomass (for instance wood
chips) can have higher moisture content than coal (especially if the coal has been dried).
When this is the case, more of the wood's inherent energy must be spent solely on
evaporating moisture, compared to the drier coal, which means that the amount of
CO2 emitted per unit produced heat will be higher. This moisture problem can be mitigated by
modern combustion facilities.[ap]

Forest biomass on average produces 10-16% more CO 2 than coal.[62]: 3 However,

focusing on gross emissions misses the point, what counts is the net climate effect from
emissions and absorption, taken together.[63]: 386 [62]: 3–4 IEA Bioenergy concludes that the
additional CO2 from biomass "[...] is irrelevant if the biomass is derived from sustainably
managed forests."[62]: 3

Climate impacts expressed as varying with time

Time-dependent net emission estimates for forest bioenergy pathways, compared
against coal and natural gas alternative scenarios. Plus signs represents positive climate
effects, minus signs negative climate effects.[18]
The use of boreal stemwood harvested exclusively for bioenergy have a positive
climate impact only in the long term, while the use of wood residues have a positive climate
impact also in the short to medium term.[aq]

Short carbon payback/parity times are produced when the most realistic no-bioenergy
scenario is a traditional forestry scenario where "good" wood stems are harvested for lumber
production, and residues are burned or left behind in the forest or in landfills. The collection
of such residues provides material which "[...] would have released its carbon (via decay or
burning) back to the atmosphere anyway (over time spans defined by the biome's decay rate)
[...]."[64] In other words, payback and parity times depend on the decay speed. The decay speed
depends on a.) location (because decay speed is "[...] roughly proportional to temperature and
rainfall [...]"[65]), and b.) the thickness of the residues. [ar] Residues decay faster in warm and
wet areas, and thin residues decay faster than thick residues. Thin residues in warm and wet
temperate forests therefore have the fastest decay, while thick residues in cold and dry boreal
forests have the slowest decay. If the residues instead are burned in the no-bioenergy
scenario, e.g. outside the factories or at roadside in the forests, emissions are instant. In this
case, parity times approach zero.[as]

Like other scientists, the JRC staff note the high variability in carbon accounting
results, and attribute this to different methodologies. [at] In the studies examined, the JRC found
carbon parity times of 0 to 400 years for stemwood harvested exclusively for bioenergy,
depending on different characteristics and assumptions for both the forest/bioenergy system
and the alternative fossil system, with the emission intensity of the displaced fossil fuels seen

14
as the most important factor, followed by conversion efficiency and biomass growth
rate/rotation time. Other factors relevant for the carbon parity time are the initial carbon stock
and the existing harvest level; both higher initial carbon stock and higher harvest level means
longer parity times.[66] Liquid biofuels have high parity times because about half of the energy
content of the biomass is lost in the processing.[au]

Climate impacts expressed as static numbers

Greenhouse gas emissions from wood pellet production and transport

from the US to the EU.[67]
EU's Joint Research Centre has examined a number of bioenergy emission estimates
found in literature, and calculated greenhouse gas savings percentages for bioenergy
pathways in heat production, transportation fuel production and electricity production, based
on those studies. The calculations are based on the attributional LCA accounting principle. It
includes all supply chain emissions, from raw material extraction, through energy and
material production and manufacturing, to end-of-life treatment and final disposal. It also
includes emissions related to the production of the fossil fuels used in the supply chain. It
excludes emission/absorption effects that takes place outside its system boundaries, for
instance market related, biogeophysical (e.g. albedo), and time-dependent effects. The
authors conclude that "[m]ost bio-based commodities release less GHG than fossil products
along their supply chain; but the magnitude of GHG emissions vary greatly with logistics,
type of feedstocks, land and ecosystem management, resource efficiency, and technology."[68]

Because of the varied climate mitigation potential for different biofuel pathways,
governments and organizations set up different certification schemes to ensure that biomass
use is sustainable, for instance the RED (Renewable Energy Directive) in the EU and the ISO
standard 13065 by the International Organization for Standardization. [69] In the US, the RFS
(Renewables Fuel Standard) limit the use of traditional biofuels and defines the minimum
life-cycle GHG emissions that are acceptable. Biofuels are considered traditional if they
achieve up to 20% GHG emission reduction compared to the petrochemical equivalent,
advanced if they save at least 50%, and cellulosic if the save more than 60%.[av]

The EU's Renewable Energy Directive (RED) states that the typical greenhouse gas
emissions savings when replacing fossil fuels with wood pellets from forest residues for heat
production varies between 69% and 77%, depending on transport distance: When the distance
is between 0 and 2500 km, emission savings is 77%. Emission savings drop to 75% when the
distance is between 2500 and 10 000 km, and to 69% when the distance is above 10 000 km.
When stemwood is used, emission savings varies between 70% and 77%, depending on
transport distance. When wood industry residues are used, savings varies between 79% and
87%.[aw]

Since the long payback and parity times calculated for some forestry projects is seen
as a non-issue for energy crops (except in the cases mentioned above), researchers instead
calculate static climate mitigation potentials for these crops, using LCA-based carbon
accounting methods. A particular energy crop-based bioenergy project is considered carbon

15
positive, carbon neutral or carbon negative based on the total amount of CO 2 equivalent
emissions and absorptions accumulated throughout its entire lifetime: If emissions during
agriculture, processing, transport and combustion are higher than what is absorbed (and
stored) by the plants, both above and below ground, during the project's lifetime, the project
is carbon positive. Likewise, if total absorption is higher than total emissions, the project is
carbon negative. In other words, carbon negativity is possible when net carbon
accumulation more than compensates for net lifecycle greenhouse gas emissions.

Typically, perennial crops sequester more carbon than annual crops because the root
buildup is allowed to continue undisturbed over many years. Also, perennial crops avoid the
yearly tillage procedures (plowing, digging) associated with growing annual crops. Tilling
helps the soil microbe populations to decompose the available carbon, producing CO2.[ax][63]: 393

There is now (2018) consensus in the scientific community that "[...] the GHG
[greenhouse gas] balance of perennial bioenergy crop cultivation will often be favourable
[...]", also when considering the implicit direct and indirect land use changes.[70]: 150

Albedo and evapotranspiration

Forests generally have a low albedo because the majority of the ultraviolet and visible
spectrum is absorbed through photosynthesis. For this reason, the greater heat absorption by
trees could offset some of the carbon benefits of afforestation (or offset the negative climate
impacts of deforestation). In other words: The climate change mitigation effect of carbon
sequestration by forests is partially counterbalanced in that reforestation can decrease the
reflection of sunlight (albedo).[71]
Environmental impacts
The environmental impacts of biomass production need to be taken into account. For
instance, in 2022, IEA stated that "bioenergy is an important pillar of decarbonisation in the
energy transition as a near zero-emission fuel", and that "more efforts are needed to
accelerate modern bioenergy deployment to get on track with the Net Zero Scenario [....]
while simultaneously ensuring that bioenergy production does not incur negative social and
environmental consequences."[72]

Sustainable forestry and forest protection

IPCC states that there is disagreement about whether the global forest is shrinking or
not, and quote research indicating that tree cover has increased 7.1% between 1982 and 2016.
[63]: 367
The IPCC writes: "While above-ground biomass carbon stocks are estimated to be
declining in the tropics, they are increasing globally due to increasing stocks in temperate and
boreal forests [...]."[63]: 385

Old trees have a very high carbon absorption rate, and felling old trees means that this
large potential for future carbon absorption is lost. [61]: 3 There is also a loss of soil carbon due
to the harvest operations.[61]: 3

Old trees absorb more CO2 than young trees because of the larger leaf area in full-
grown trees.[74] However, the old forest (as a whole) will eventually stop absorbing
CO2 because CO2 emissions from dead trees cancel out the remaining living trees'
CO2 absorption.[ay] The old forest (or forest stands) are also vulnerable for natural disturbances
that produces CO2. The IPCC found that "[...] landscapes with older forests have accumulated
more carbon but their sink strength is diminishing, while landscapes with younger forests

16
contain less carbon but they are removing CO2 from the atmosphere at a much higher rate
[...]."[63]: 386

The IPCC states that the net climate effect from conversion of unmanaged to managed
forest can be positive or negative, depending on circumstances. The carbon stock is reduced,
but since managed forests grow faster than unmanaged forests, more carbon is absorbed.
Positive climate effects are produced if the harvested biomass is used efficiently. [63]: 351 There is
a tradeoff between the benefits of having a maximized forest carbon stock, not absorbing any
more carbon, and the benefits of having a portion of that carbon stock "unlocked", and
instead working as a renewable fossil fuel replacement tool, for instance in sectors which are
difficult or expensive to decarbonize.[32][az]

The "competition" between locked-away and unlocked forest carbon might be won by
the unlocked carbon: "In the long term, using sustainably produced forest biomass as a
substitute for carbon-intensive products and fossil fuels provides greater permanent
reductions in atmospheric CO2 than preservation does."[75]: 39

IEA Bioenergy writes: "forests managed for producing sawn timber, bioenergy and
other wood products can make a greater contribution to climate change mitigation than
forests managed for conservation alone." Three reasons are given:[76]

1. reducing ability to act as a carbon sink when the forest matures.

2. Wood products can replace other materials that emitted more GHGs
during production.
3. "Carbon in forests is vulnerable to loss through natural events such as
insect infestations or wildfires"
Data from FAO show that most wood pellets are produced in regions dominated by
sustainably managed forests, such as Europe and North America. Europe (including Russia)
produced 54% of the world's wood pellets in 2019, and the forest carbon stock in this area
increased from 158.7 to 172.4 Gt between 1990 and 2020. In the EU, above-ground forest
biomass increases with 1.3% per year on average, however the increase is slowing down
because the forests are maturing.[77]

Old-growth spruce forest in France Plantation forest in Hawaii

United Kingdom Emissions Trading System allows operators of CO2 generating

installations to apply zero emissions factor for the fraction used for non-energy purposes,
17
while energy purposes (electricity generation, heating) require additional sustainability
certification on the biomass used.[78]

Forest area increase in the EU 1990–2020 Sankey diagram that shows the flow of biomass from
forest to wood products, paper and energy in Sweden.[79]

Biodiversity

Classification scheme for win-win (green), trade-off

(orange), and lose-lose (red) scenarios caused by additional bioenergy pathways in the EU. [12]:
107
Short term climate and biodiversity impacts for 3 alternative bioenergy pathways in the EU
(forest residues, afforestation and conversion to forest plantation.) Short term is here defined
as a period of 0–20 years, medium term 30-50 years, and long term over 50 years.[12]: 146
Biomass production for bioenergy can have negative impacts on biodiversity. [5] Oil
palm and sugar cane are examples of crops that have been linked to reduced biodiversity.[80] In
addition, changes in biodiversity also impacts primary production which naturally effects
decomposition and soil heterotrophic organisms.[81]

Win-win scenarios (good for climate, good for biodiversity) include:[12]: 8–149

 Increased use of whole trees from coppice forests, increased use of thin forest
residues from boreal forests with slow decay rates, and increased use of all kinds of
residues from temperate forests with faster decay rates;
 Multi-functional bioenergy landscapes, instead of expansion of monoculture
plantations; [82]
 Afforestation of former agricultural land with mixed or naturally regenerating
forests.
Win-lose scenarios (good for the climate, bad for biodiversity) include afforestation
on ancient, biodiversity-rich grassland ecosystems which were never forests, and
afforestation of former agricultural land with monoculture plantations.[12]: 125–147

Lose-win scenarios (bad for the climate, good for biodiversity) include natural forest
expansion on former agricultural land.[12]: 125–147

18
 Lose-lose scenarios include increased use of thick forest residues like stumps from
some boreal forests with slow decay rates, and conversion of natural forests into forest
plantations.[12]: 8–147

Pollution

Simple traditional use of biomass for cooking or heating (combustion

of wood logs).
Other problems are pollution of soil and water from fertiliser/pesticide use, [83] and
emission of ambient air pollutants, mainly from open field burning of residues.[84]

The traditional use of wood in cook stoves and open fires produces pollutants, which
can lead to severe health and environmental consequences. However, a shift to modern
bioenergy contribute to improved livelihoods and can reduce land degradation and impacts
on ecosystem services.[63]: 375 According to the IPCC, there is strong evidence that modern
bioenergy have "large positive impacts" on air quality. [85] Traditional bioenergy is inefficient
and the phasing out of this energy source has both large health benefits and large economic
benefits.[32] When combusted in industrial facilities, most of the pollutants originating from
woody biomass reduce by 97-99%, compared to open burning.[86] Combustion of woody
biomass produces lower amounts of particulate matter than coal for the same amount of
electricity generated.[87]

References
1. ^ "Biomass explained - U.S. Energy Information Administration (EIA)". www.eia.gov.
Retrieved 2023-01-24.
2. ^ Darby, Thomas. "What Is Biomass Renewable Energy". Real World Energy. Archived
from the original on 2014-06-08. Retrieved 12 June 2014.
3. ^ Correa, Diego F.; Beyer, Hawthorne L.; Fargione, Joseph E.; Hill, Jason D.; et al.
(2019). "Towards the implementation of sustainable biofuel production systems". Renewable
and Sustainable Energy Reviews. 107: 250–
263. Bibcode:2019RSERv.107..250C. doi:10.1016/j.rser.2019.03.005. ISSN 1364-0321. S2
CID 117472901. Archived from the original on 17 July 2021. Retrieved 7 February 2021.
4. ^ Daley, Jason (24 April 2018). "The EPA Declared That Burning Wood Is Carbon Neutral.
It's Actually a Lot More Complicated". Smithsonian Magazine. Archived from the original
on 30 June 2021. Retrieved 2021-09-14.
5. ^ Jump up to:a b Gasparatos et al. 2017.
6. ^ Jump up to:a b Tester 2012, p. 512.
7. ^ Jump up to:a b c Smil 2017a, p. 162.
8. ^ "Bioenergy – Analysis". IEA. Retrieved 2023-01-13.
9. ^ "Bioenergy Basics". Energy.gov. Retrieved 2023-01-13.
10. ^ "Biomass explained - U.S. Energy Information Administration (EIA)". www.eia.gov.
Retrieved 2023-01-13.

19
11. ^ "Renewable Energy Sources and Climate Change Mitigation. Special Report of the
Intergovernmental Panel on Climate Change" (PDF). IPCC. Archived (PDF) from the
original on 2019-04-12.
12. ^ Jump up to:a b c d e f g h i European Commission. Joint Research Centre. (2021). The use of
woody biomass for energy production in the EU. LU: Publications
Office. doi:10.2760/831621. ISBN 978-92-76-27867-2.
13. ^ Jump up to:a b c IRENA (2014). "Global bioenergy supply and demand projections – a
working paper for REmap 2030" International Renewable Energy Agency.
14. ^ Eggers, Jeannette; Melin, Ylva; Lundström, Johanna; Bergström, Dan; Öhman, Karin
(2020-05-16). "Management Strategies for Wood Fuel Harvesting—Trade-Offs with
Biodiversity and Forest Ecosystem Services". Sustainability. 12 (10):
4089. doi:10.3390/su12104089. ISSN 2071-1050.
15. ^ WBA 2016, p. 4.
16. ^ WBA (2019) GLOBAL BIOENERGY STATISTICS 2019 World Bioenergy Association
17. ^ JRC 2019, p. 3.
18. ^ Jump up to:a b JRC 2014, p. 75.
19. ^ Jump up to:a b c IEA 2021d.
20. ^ "Household air pollution and health: fact sheet". WHO. 8 May 2018. Retrieved 2020-11-
21.
21. ^ "Goal 7: Ensure access to affordable, reliable, sustainable and modern energy for
all". SDG Tracker. Archived from the original on 2 February 2021. Retrieved 12
March 2021.
22. ^ ETIP Bioenergy 2022.
23. ^ IRENA 2014, p. 20-21.
24. ^ IEA 2021c.
25. ^ Camia et al. 2021, p. 7.
26. ^ Camia et al. 2018, p. 6.
27. ^ Jump up to:a b c d e f g h Cowie, Annette L.; Berndes, Göran; Bentsen, Niclas Scott; Brandão,
Miguel; Cherubini, Francesco; Egnell, Gustaf; George, Brendan; Gustavsson, Leif;
Hanewinkel, Marc; Harris, Zoe M.; Johnsson, Filip; Junginger, Martin; Kline, Keith L.;
Koponen, Kati; Koppejan, Jaap (2021). "Applying a science-based systems perspective to
dispel misconceptions about climate effects of forest bioenergy". GCB Bioenergy. 13 (8):
1210–1231. Bibcode:2021GCBBi..13.1210C. doi:10.1111/gcbb.12844. hdl:10044/1/89123.
ISSN 1757-1693. S2CID 235792241.
28. ^ Jump up to:a b van den Born et al. 2014, p. 20, table 4.2.
29. ^ ETIP Bioenergy 2020.
30. ^ IEA 2019.
31. ^ van den Born et al. 2014, p. 2, 21.
32. ^ Jump up to:a b c d "What does net-zero emissions by 2050 mean for bioenergy and land use?
– Analysis". IEA. 31 May 2021. Retrieved 2023-01-19.
33. ^ Jump up to:a b c d EIA 2022.
34. ^ Basu et al. 2013, pp. 171–176.
35. ^ Koukoulas 2016, p. 12.
36. ^ Wild 2015, p. 72.
37. ^ Smil 2015, p. 13.
38. ^ Renewable Energy 2021, pp. 473–483.
39. ^ EIA 2021.
40. ^ Akhtar, Krepl & Ivanova 2018.
41. ^ Liu et al. 2011.
42. ^ "Biochemical Conversion of Biomass". BioEnergy Consult. 2014-05-29. Retrieved 2016-
10-18.

20
43. ^ Correa, Diego F.; Beyer, Hawthorne L.; Fargione, Joseph E.; Hill, Jason D.; et al.
(2019). "Towards the implementation of sustainable biofuel production systems". Renewable
and Sustainable Energy Reviews. 107: 250–
263. Bibcode:2019RSERv.107..250C. doi:10.1016/j.rser.2019.03.005. ISSN 1364-0321. S2
CID 117472901. Archived from the original on 17 July 2021. Retrieved 7 February 2021.
44. ^ Daley, Jason (24 April 2018). "The EPA Declared That Burning Wood Is Carbon Neutral.
It's Actually a Lot More Complicated". Smithsonian Magazine. Archived from the original
on 30 June 2021. Retrieved 14 September 2021.
45. ^ World Health Organization 2016, p. 73.
46. ^ IPCC 2014, p. 616.
47. ^ "Biofuels explained: Ethanol". US Energy Information Administration. 18 June
2020. Archived from the original on 14 May 2021. Retrieved 16 May 2021.
48. ^ Foley, Jonathan (5 March 2013). "It's Time to Rethink America's Corn System". Scientific
American. Archived from the original on 3 January 2020. Retrieved 16 May 2021.
49. ^ Ayompe, Lacour M.; Schaafsma, M.; Egoh, Benis N. (1 January 2021). "Towards
sustainable palm oil production: The positive and negative impacts on ecosystem services
and human wellbeing". Journal of Cleaner Production. 278:
123914. Bibcode:2021JCPro.27823914A. doi:10.1016/j.jclepro.2020.123914. ISSN 0959-
6526. S2CID 224853908.
50. ^ Lustgarten, Abrahm (20 November 2018). "Palm Oil Was Supposed to Help Save the
Planet. Instead It Unleashed a Catastrophe". The New York Times. ISSN 0362-
4331. Archived from the original on 17 May 2019. Retrieved 15 May 2019.

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