HOME

TheInfoList




Biomass is plant or animal material used as fuel to produce
electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon in which an object changes its positio ...

electricity
or
heat In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these ...

heat
. Examples are wood,
energy crop Energy crops are low-cost and low-maintenance crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. Crops may refer either to the harvested parts or to the harvest in a more refined state. Most crops ar ...
s and waste from forests, yards, or farms. Since biomass technically can be used as a fuel directly (e.g. wood logs), some people use the terms biomass and
biofuel Biofuel is fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several di ...

biofuel
interchangeably. More often than not, the word biomass simply denotes the biological raw material the fuel is made of. The word biofuel is usually reserved for ''liquid'' or ''gaseous'' fuels, used for transportation. The U.S. Energy Information Administration (EIA) follows this naming practice. The
IPCC The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations The United Nations (UN) is an intergovernmental organization that aims to maintain international peace and international security, s ...
(Intergovernmental Panel on Climate Change) defines bioenergy as a renewable form of energy. In 2017 the IEA (International Energy Agency) described bioenergy as the most important source of renewable energy. IEA also argue that the current rate of bioenergy deployment is well below the levels required in low carbon scenarios, and that accelerated deployment is urgently needed. Researchers have disputed that the use of forest biomass for energy is
carbon neutral Carbon neutrality refers to achieving net-zero carbon dioxide emissions. This can be done by balancing emissions of carbon dioxide with its removal (often through carbon offsetting) or by eliminating emissions from society (the transition to the ...
.


Biomass feedstocks

Wood and wood residues is the largest biomass energy source today. Wood can be used as a fuel directly or processed into
pellet fuel Pellet fuels (or pellets) are biofuels made from compressed organic matter or biomass. Pellets can be made from any one of five general categories of biomass: industrial waste and co-products, food waste, Crop residue, agricultural residues, energy ...
or other forms of fuels. Other plants can also be used as fuel, for instance
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can ...

corn
,
switchgrass ''Panicum virgatum'', commonly known as switchgrass, is a perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a ...
,
miscanthus ''Miscanthus'', or silvergrass, is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ...

miscanthus
and
bamboo Bamboos are a diverse group of evergreen perennial plant, perennial flowering plants in the subfamily (biology), subfamily Bambusoideae of the grass family ''Poaceae''. The origin of the word "bamboo" is uncertain, but it probably comes from t ...

bamboo
. The main
waste energy upright=1.5, Spittelau incineration plant is one of several plants that provide district heating in Vienna. Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the prima ...
feedstocks are wood waste,
agricultural waste Green waste, also known as "biological waste," is any organic waste that can be composted. It is most usually composed of refuse from gardens such as grass clippings or leaves, and domestic or industrial kitchen wastes. Green waste does not inclu ...
,
municipal solid waste Municipal solid waste (MSW), commonly known as trash or garbage in the American English, United States and rubbish in British English, Britain, is a List of waste types, waste type consisting of everyday items that are discarded by the public. ...
,
manufacturing waste Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories A factory, manufacturing plant or a production plant is an industrial ...
, and
landfill gas Landfill gas is a mix of different gases created by the action of microorganisms within a landfill as they decompose Biodegradable waste, organic waste, including for example, food waste and paper waste. Landfill gas is approximately forty to sixt ...
.
Sewage sludge Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewerage, sewer system. Sewage consists of wastewater discharged fro ...
is another source of biomass. There is ongoing research involving algae or algae-derived biomass. Other biomass feedstocks are
enzyme Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into different molecules known as . Almost all in the need in order to occu ...

enzyme
s or
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
from various sources, grown in
cell culture Cell culture is the process by which cell (biology), cells are grown under controlled conditions, generally outside their natural environment. After the cells of interest have been Cell isolation, isolated from living tissue, they can subsequentl ...

cell culture
s or
hydroponics Hydroponics is a type of horticulture and a subset of #Passive sub-irrigation, hydroculture which involves growing plants (usually crops) without soil, by using mineral nutrient Solution (chemistry), solutions in an water, aqueous solvent. Terres ...
. Biomass is also used to produce fibers and industrial
chemicals A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wit ...
. Based on the source of biomass,
biofuel Biofuel is fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several di ...

biofuel
s are classified broadly into three major categories: First-generation biofuels are derived from food sources, such as
sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differen ...

sugarcane
and
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can ...

corn
starch. Sugars present in this biomass are fermented to produce
bioethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entiti ...
, an alcohol fuel which serve as an additive to gasoline, or in a
fuel cell A fuel cell is an that converts the of a fuel (often ) and an (often oxygen) into electricity through a pair of reactions. Fuel cells are different from most in requiring a continuous source of fuel and oxygen (usually from air) to sustai ...

fuel cell
to produce electricity.
Second-generation biofuelsSecond-generation biofuels, also known as advanced biofuels, are fuels that can be manufactured from various types of non-food biomass Biomass is plant or animal material used as fuel to produce electricity or heat. Examples are wood, energy crops ...
utilize non-food-based biomass sources such as
perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and incl ...
energy crops (low input crops), and agricultural/municipal waste. Proponents argue that there is huge potential for second generation biofuels. Third-generation biofuels refer to those derived from microalgae.


Biomass conversion

Upgrading raw biomass to higher grade fuels can be achieved by different methods, broadly classified as thermal, chemical, or biochemical.


Thermal conversions

Thermal conversion processes use heat as the dominant mechanism to upgrade biomass into a better and more practical fuel. The basic alternatives are
torrefaction Torrefaction of biomass, e.g., wood or grain, is a mild form of pyrolysis at temperatures typically between 200 and 320 °C. Torrefaction changes biomass properties to provide a better fuel quality for combustion and gasification applications. ...

torrefaction
,
pyrolysis The pyrolysis (or devolatilization) process is the of materials at elevated temperatures in an inert atmosphere. It involves a change of . The word is coined from the -derived s ''pyro'' "fire" and ' "separating". Pyrolysis is most commonly us ...

pyrolysis
, and
gasification Gasification is a process that converts biomass Biomass is plant or animal material used as fuel to produce electricity or heat. Examples are wood, energy crops and waste from forests, yards, or farms. Since biomass technically can be used as ...

gasification
, these are separated principally by the extent to which the chemical reactions involved are allowed to proceed (mainly controlled by the availability of oxygen and conversion temperature). There are other less common, more experimental or proprietary thermal processes that may offer benefits, such as
hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC ...
upgrading. Some have been developed for use on high moisture content biomass, including aqueous slurries, and allow them to be converted into more convenient forms.


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. Biomass can be converted into multiple commodity chemicals.


Biochemical conversion

As biomass is a natural material, many highly efficient biochemical processes have developed in nature to break down the molecules of which biomass is composed, and many of these biochemical conversion processes can be harnessed. In most cases, microorganisms are used to perform the conversion process:
anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to Waste management, manage waste or to produce fuels. Muc ...

anaerobic digestion
,
fermentation Fermentation is a metabolism, metabolic process that produces chemical changes in organic Substrate (chemistry), substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in ...
, and
composting Compost is a mixture of ingredients used to fertilize and improve the soil. It is commonly prepared by decomposing plant and food waste and recycling Recycling is the process of converting waste Waste (or wastes) are unwanted ...

composting
.
Glycoside hydrolases 1HNY, a glycoside hydrolase Glycoside hydrolases (also called glycosidases or glycosyl hydrolases) catalysis, catalyze the hydrolysis of glycosidic bonds in polysaccharide, complex sugars. They are extremely common enzymes with roles in nature incl ...
are the enzymes involved in the degradation of the major fraction of biomass, such as polysaccharides present in starch and lignocellulose. Thermostable variants are gaining increasing roles as catalysts in biorefining applications, since recalcitrant biomass often needs thermal treatment for more efficient degradation.


Electrochemical conversions

Biomass can be directly converted to electrical energy via electrochemical (electrocatalytic) oxidation of the material. This can be performed directly in a
direct carbon fuel cellA Direct Carbon Fuel Cell (DCFC) is a fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen fuel, hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox rea ...
, direct liquid fuel cells such as direct ethanol fuel cell, a direct methanol fuel cell, a direct
formic acid fuel cellFormic acid fuel cells (direct formic acid fuel cells or DFAFCs) are a subcategory of proton-exchange membrane fuel cell Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel ce ...
, a L-ascorbic Acid Fuel Cell (vitamin C fuel cell), and a
microbial fuel cellMicrobial fuel cell (MFC) is a type of bioelectrochemical fuel cell system that generates electric current by diverting electrons produced from the microbial oxidation of reduced compounds (also known as fuel or electron donor) on the anode to oxidi ...
. The fuel can also be consumed indirectly via a
fuel cell A fuel cell is an that converts the of a fuel (often ) and an (often oxygen) into electricity through a pair of reactions. Fuel cells are different from most in requiring a continuous source of fuel and oxygen (usually from air) to sustai ...

fuel cell
system containing a reformer which converts the biomass into a mixture of CO and H2 before it is consumed in the fuel cell.


Carbon neutrality for forest biomass

IEA defines carbon neutrality and carbon negativity like so: «Carbon neutrality, or 'net zero,' means that any CO2 released into the atmosphere from human activity is balanced by an equivalent amount being removed. Becoming carbon negative requires a company, sector or country to remove more CO2 from the atmosphere than it emits.» The actual carbon intensity of biomass varies with production techniques and transportation lengths. According to the EU, typical greenhouse gas emissions savings when replacing fossil fuels with wood pellets from forest residues is 77% when the transport distance is between 0 and 500 km, also 77% when the transport distance is between 500 and 2500 km, 75% when the distance is between 2500 and 10 000 km, and 69% when the distance is above 10 000 km. When stemwood is used, the savings change only marginally, from between 70 and 77%. When wood industry residues are used, savings increase to between 79 and 87%. Likewise, Hanssen et al. argue that greenhouse gas emissions savings from wood pellets produced in the US southeast and shipped to the EU is between 65 and 75%, compared to fossil fuels. They estimate that average net GHG emissions from wood pellets imported from the USA and burnt for electricity in the EU amounts to approximately 0.2 kg CO2 equivalents per kWh, while average emissions from the mix of fossil fuels that is currently burnt for electricity in the EU amounts to 0.67 kg CO2-eq per kWh (see chart on the right). Ocean transport emissions amounts to 7% of the fossil fuel mix emissions per produced kWh (equivalent to 93 kg CO2-eq/t vs 1288 kg CO2/t). IEA Bioenergy estimates that in a scenario where Canadian wood pellets are used to totally replace coal use in a European coal plant, the specific emissions originating from ocean transport of the pellets, going from Vancouver to Rotterdam, amounts to approximately 2% of the plant's total coal-related emissions.


More CO2 from wood combustion than coal combustion

When combusted in combustion facilities with the same heat-to-electricity conversion efficiency, oven dry wood emits slightly less CO2 per unit of heat produced, compared to oven dry coal. However, many biomass combustion facilities are relatively small and inefficient, compared to the typically much larger coal plants. Further, 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. Some research groups (e.g. Chatham House) therefore argue that « ..the use of woody biomass for energy will release higher levels of emissions than coal » How much «extra» CO2 that is released depends on local factors. Some research groups estimate relatively low extra emissions. IEA Bioenergy for instance estimates 10%. The bioenergy consultant group FutureMetrics argue that wood pellets with 6% moisture content emits 22% ''less'' CO2 for the same amount of produced heat, compared to sub-bituminous coal with 15% moisture, when both fuels are combusted in facilities with the same conversion efficiency (here 37%). Likewise, they state that « dried wood at MC’s oisture contentbelow 20% have the same or less CO2 emission per MMBTU illion_British_thermal_units.html" ;"title="British_thermal_unit.html" ;"title="illion British thermal unit">illion British thermal units">British_thermal_unit.html" ;"title="illion British thermal unit">illion British thermal unitsas most coal. Wood pellets at under 10% MC result in less CO2 emission than any coal under otherwise equal circumstances.» (Moisture content in wood pellets is usually below 10%, as defined in the ISO standard 17225-2:2014.) However, when raw wood chips are used instead (45% moisture content), this wood biomass emits 9% ''more'' CO2 than coal in general, for the same amount of produced heat. According to Indiana Center for Coal Technology Research, the coal type anthracite typically contains below 15% moisture, while bituminous contains 2–15%, sub-bituminous 10–45%, and lignite 30–60%. The most common coal type in Europe is lignite. Other research groups estimate relatively high extra emissions. The Manomet Center for Conservation Sciences for instance, argue that for smaller scale utilities, with 32% conversion efficiency for coal, and 20-25% for biomass, coal emissions are 31% less than for wood chips. Assumed moisture content for wood chips is 45%, as above. The assumed moisture content for coal is not provided. The IPCC (Intergovernmental Panel on Climate Change) put their «extra CO2» estimates for biomass at roughly 16% extra for wood over coal in general, somewhere in the middle compared to the estimates above. Is the extra CO2 from biomass a problem? IPCC argues that focusing on gross emissions misses the point, what counts is the net effect of emissions and absorption taken together: «Estimating gross emissions only, creates a distorted representation of human impacts on the land sector carbon cycle. While forest harvest for timber and fuelwood and land-use change (deforestation) contribute to gross emissions, to quantify impacts on the atmosphere, it is necessary to estimate net emissions, that is, the balance of gross emissions and gross removals of carbon from the atmosphere through forest regrowth »IEA Bioenergy provide a similar argument: «It is incorrect to determine the climate change effect of using biomass for energy by comparing GHG emissions at the point of combustion.» They also argue that « the misplaced focus on emissions at the point of combustion blurs the distinction between fossil and biogenic carbon, and it prevents proper evaluation of how displacement of fossil fuels with biomass affects the development of atmospheric GHG concentrations.» IEA Bioenergy conclude that the additional CO2 from biomass « is irrelevant if the biomass is derived from sustainably managed forests.» What is sustainable managed forests? The IPCC writes: «Sustainable Forest Management (SFM) is defined as ‘the stewardship and use of forests and forest lands in a way, and at a rate, that maintains their biodiversity, productivity, regeneration capacity, vitality and their potential to fulfill, now and in the future, relevant ecological, economic and social functions, at local, national, and global levels, and that does not cause damage to other ecosystems’ This SFM definition was developed by the Ministerial Conference on the Protection of Forests in Europe and has since been adopted by the Food and Agriculture Organization f the United Nations (FAO)» Further, IPCC writes: «Sustainable forest management can prevent deforestation, maintain and enhance carbon sinks and can contribute towards GHG emissions-reduction goals. Sustainable forest management generates socio-economic benefits, and provides fibre, timber and biomass to meet society’s growing needs.» In the context of CO2 mitigation, the key measure regarding sustainability is the size of the forest carbon stock. In a research paper for FAO, Reid Miner writes: «The core objective of all sustainable management programmes in production forests is to achieve a long-term balance between harvesting and regrowth. e practical effect of maintaining a balance between harvesting and regrowth is to keep long-term carbon stocks stable in managed forests.» Is the forest carbon stock stable? Globally, the forest carbon stock has decreased 0.9% and tree cover 4.2% between 1990 and 2020, according to FAO. 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. 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 »


Forest protection

Some research groups seem to want more than «just» sustainably managed forests, they want to realize the forests ''full'' carbon storage potential. For instance EASAC writes: «There is a real danger that present policy over-emphasises the use of forests in energy production instead of increasing forest stocks for carbon storage.» Further, they argue that « it is the older, longer-rotation forests and protected old-growth forests that exhibit the highest carbon stocks.» Chatham House argues that old trees have a very high carbon absorption, and that felling old trees means that this large potential for future carbon absorption is lost. In addition they argue that there is a loss of soil carbon due to the harvest operations. Research show that old trees absorb more CO2 than young trees, because of the larger leaf area in full grown trees. 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. The old forest (or forest stands) are also vulnerable for natural disturbances that produces CO2. The IPCC writes: «When vegetation matures or when vegetation and soil carbon reservoirs reach saturation, the annual removal of CO2 from the atmosphere declines towards zero, while carbon stocks can be maintained (high confidence). However, accumulated carbon in vegetation and soils is at risk from future loss (or sink reversal) triggered by disturbances such as flood, drought, fire, or pest outbreaks, or future poor management (high confidence).» Summing up, IPCC writes that « landscapes with older forests have accumulated more carbon but their sink strength is diminishing, while landscapes with younger forests contain less carbon but they are removing CO2 from the atmosphere at a much higher rate ..» Regarding soil carbon, the IPCC writes: «Recent studies indicate, that effects of forest management actions on soil C
arbon , neighboring_municipalities= Egnach Egnach is a Municipalities of Switzerland, municipality of the district of Arbon (district), Arbon in the Cantons of Switzerland, canton of Thurgau in Switzerland. History Egnach is first mentioned in 1155 as ...

arbon
stocks can be difficult to quantify and reported effects have been variable and even contradictory (see Box 4.3a).» Because the «current scientific basis is not sufficient», the IPCC will not currently provide soil carbon emission factors for forest management. Regarding the net climate effect of conversion from natural to managed forests, the IPCC argues that it can swing both ways: «SFM ustainable forest managementapplied at the landscape scale to existing unmanaged forests can first reduce average forest carbon stocks and subsequently increase the rate at which CO2 is removed from the atmosphere, because net ecosystem production of forest stands is highest in intermediate stand ages (Kurz et al. 2013; Volkova et al. 2018; Tang et al. 2014). The net impact on the atmosphere depends on the magnitude of the reduction in carbon stocks, the fate of the harvested biomass (i.e. use in short – or long-lived products and for bioenergy, and therefore displacement of emissions associated with GHG-intensive building materials and fossil fuels), and the rate of regrowth. Thus, the impacts of SFM on one indicator (e.g., past reduction in carbon stocks in the forested landscape) can be negative, while those on another indicator (e.g., current forest productivity and rate of CO2 removal from the atmosphere, avoided fossil fuel emissions) can be positive. Sustainably managed forest landscapes can have a lower biomass carbon density than unmanaged forest, but the younger forests can have a higher growth rate, and therefore contribute stronger carbon sinks than older forests (Trofymow et al. 2008; Volkova et al. 2018; Poorter et al. 2016).» In other words, 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. When put to work, this carbon is constantly replacing carbon in fossil fuels used in for instance heat production and baseload electricity production – sectors where it is un-economical or impossible to use intermittent power sources like wind or solar. Being a renewable carbon source, the unlocked portion keep cycling back and forth between forests and forest products like lumber and wood pellets. For each cycle it replaces more and more of the fossil based alternatives, e.g. cement and coal. FAO researcher Reid Miner argues that the «competition» between locked-away and unlocked forest carbon is 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.» Summing up the above, IEA Bioenergy writes: «As the IPCC has pointed out in several reports, forests managed for producing sawn timber, bioenergy and other wood products can make a greater contribution to
climate change mitigation Climate change mitigation consists of actions to limit global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been , but the current cha ...
than forests managed for conservation alone, for three reasons. First, the sink strength diminishes as conservation forests approach maturity. Second, wood products displace GHG-intensive materials and fossil fuels. Third, carbon in forests is vulnerable to loss through natural events such as insect infestations or wildfires, as recently seen in many parts of the world including Australia and California. Managing forests can help to increase the total amount of carbon sequestered in the forest and wood products carbon pools, reduce the risk of loss of sequestered carbon, and reduce fossil fuel use.» The IPCC further suggest that the possibility to make a living out of forestry incentivize sustainable forestry practices: « SFM ustainable forest managementaimed at providing timber, fibre, biomass and non-timber resources can provide long-term livelihood for communities, reduce the risk of forest conversion to non-forest uses (settlement, crops, etc.), and maintain land productivity, thus reducing the risks of land degradation » Further: «By providing long-term livelihoods for communities, sustainable forest management can reduce the extent of forest conversion to non-forest uses (e.g., cropland or settlements) (high confidence).» The National Association of University Forest Resources Programs agrees: «Research demonstrates that demand for wood helps keep land in forest and incentivizes investments in new and more productive forests, all of which have significant carbon benefits. Failing to consider the effects of markets and investment on carbon impacts can distort the characterization of carbon impacts from forest biomass energy.» Favero et al. focus on the potential future increase in demand and argues: «Increased bioenergy demand increases forest carbon stocks thanks to afforestation activities and more intensive management relative to a no-bioenergy case higher biomass demand will increase the value of timberland, incentivize additional investment in forest management and afforestation, and result in greater forest carbon stocks over time». Possibly strengthening the arguments above, data from FAO show that most wood pellets are produced in regions dominated by sustainably managed forests. 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. Likewise, North America produced 29% of the worlds pellets in 2019, while forest carbon stock increased from 136.6 to 140 Gt in the same period. Carbon stock decreased from 94.3 to 80.9 Gt in Africa, 45.8 to 41.5 Gt in South and Southeast Asia combined, 33.4 to 33.1 Gt in Oceania, 5 to 4.1 Gt in Central America, and from 161.8 to 144.8 Gt in South America. Wood pellet production in these areas combined was 13.2% in 2019. Chatham House answers the above argument like so: «Forest carbon stock levels may stay the same or increase for reasons entirely unconnected with use for energy.»


Carbon payback time

Some research groups still argue that even if the European and North American forest carbon stock is increasing, it simply takes too long for harvested trees to grow back. EASAC for instance argues that since the world is on track to pass by the agreed target of 1.5 degrees temperature increase already in a decade or so, CO2 from burnt roundwood, which resides in the atmosphere for many decades before being re-absorbed, make it harder to achieve this goal. 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, 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). Chatham House agrees, and in addition argues that there could be tipping points along the temperature scale where warming accelerates. Chatham House also argues that various types of roundwood (mostly pulpwood) is used in pellet production in the USA. FutureMetrics argues that it makes no sense for foresters to sell sawlog-quality roundwood to pellet mills, since they get a lot more money for this part of the tree from sawmills. Foresters make 80-90% of their income from sawlog-quality roundwood (the lower and thicker straigth part of the tree stem), and only 10-15% from pulpwood, defined as a.) the middle part of mature trees (the thinner part of the stem that often bends a little, plus branches) and b.) tree thinnings (small, young trees cleared away for increased productivity of the whole forest stand.) This low-value biomass is mainly sold to pulp mills for paper production, but in some cases also to pellet mills for pellet production. Pellets are typically made from sawmill residues in areas where there are sawmills, and from pulpwood in areas without sawmills. Chatham House further argue that almost all available sawmill residue is already being utilized for pellet production, so there is no room for expansion. For the bioenergy sector to significantly expand in the future, more of the harvested pulpwood must go to pellet mills. However, the harvest of pulpwood (tree thinnings) removes the possibility for these trees to grow old and therefore maximize their carbon holding capacity. Compared to pulpwood, sawmill residues have lower net emissions: «Some types of biomass feedstock can be carbon-neutral, at least over a period of a few years, including in particular sawmill residues. These are wastes from other forest operations that imply no additional harvesting, and if otherwise burnt as waste or left to rot would release carbon to the atmosphere in any case.» An important presupposition for the «tree regrowth is too slow» argument is the view that carbon accounting should start when trees from particular, harvested forest stands are combusted, and not when the trees in those stands start to grow. It is within this frame of thought it becomes possible to argue that the combustion event creates a carbon debt that has to be repaid through regrowth of the harvested stands. When instead assuming that carbon accounting should start when the trees start to grow, it becomes impossible to argue that the emitted carbon constitutes debt. FutureMetrics for instance argue that the harvested carbon is not a debt but « a benefit that was earned by 30 years of management and growth » Other researchers however argue back that « what is important to climate policy is understanding the difference in future atmospheric GHG levels, with and without switching to woody biomass energy. Prior growth of the forest is irrelevant to the policy question » Undermining forester’s income may backfire however, see above for IPCC’s argument that forests which provide long-term livelihood for communities reduce the risk of forest conversion to non-forest uses.Some researchers limit their carbon accounting to particular forest stands, ignoring the carbon absorption that takes place in the rest of the forest. In opposition to this single forest stand accounting practice, other researchers include the whole forest when doing their carbon accounting. FutureMetrics for instance argue that the whole forest continually absorb CO2 and therefore immediately compensate for the relatively small amounts of biomass that is combusted in biomass plants from day to day. Likewise, IEA Bioenergy criticizes EASAC for ignoring the carbon absorption of forests as a whole, noting that there is no net loss of carbon if annual harvest do not exceed the forest’s annual growth. IPCC argue along similar lines: «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.» 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 the whole ''landscape'' (see below). When the total is calculated, natural disturbances like fires and insect infestations are subtracted, and what remains is the human influence. In this way, the whole landscape works as a proxy for calculating specifically human GHG emissions: «In the AFOLU griculture, Forestry and Other Land Usesector, the management of land is used as the best approximation of human influence and thus, estimates of emissions and removals on managed land are used as a proxy for anthropogenic emissions and removals on the basis that the preponderance of anthropogenic effects occurs on managed lands (see Vol. 4 Chapter 1). This allows for consistency, comparability, and transparency in estimation. Referred to as the Managed Land Proxy (MLP), this approach is currently recognised by the IPCC as the only universally applicable approach to estimating anthropogenic emissions and removals in the AFOLU sector (IPCC 2006, IPCC 2010).» Hanssen et al. notes that when comparing continued wood pellet production to a potential policy change where the forest instead is protected, most researchers estimate a 20–50 year carbon parity (payback) time range for the burnt wood pellets. But when instead comparing continued pellet production to the more realistic alternative scenarios of 1.) instead using all harvested biomass to produce paper, pulp or wood panels, 2.) quitting the thinning practice altogether (leaving the small trees alone, realizing more of their growth potential but at the same time reduce the growth potential of the bigger trees), and 3.) leaving the forest residue alone, so it is decomposed in the forest over time, rather than being burned almost immediately in power plants, the result is that carbon payback (parity) times for wood pellets drop to 0-21 years in all demand scenarios (see chart on the right). The estimate is based on the landscape rather than the individual forest stand carbon accounting practice.


Short-term vs long-term climate benefits

Researchers from both sides agree that in the short term, emissions might rise compared to a no-bioenergy scenario. IPCC for instance states that forest carbon emission avoidance strategies always give a short-term mitigation benefit, but argue that the long-term benefits from sustainable forestry activities are larger: Similarly, addressing the issue of climate consequences for modern bioenergy in general, IPCC states: «Life-cycle GHG emissions of modern bioenergy alternatives are usually lower than those for fossil fuels » Consequently, most of IPCC’s GHG mitigation pathways include substantial deployment of bioenergy technologies. Limited or no bioenergy pathways leads to increased climate change or shifting bioenergy’s mitigation load to other sectors. In addition, mitigation cost increases. IEA Bioenergy also prioritize the long-term benefits: «Concern about near-term emissions is not a strong argument for stopping investments that contribute to net emissions reduction beyond 2030, be it the scaling-up of battery manufacturing to support electrification of car fleets, the development of rail infrastructure, or the development of biomass supply systems and innovation to provide biobased products displacing fossil fuels, cement and other GHG-intensive products. We assert that it is critical to focus on the global emissions trajectory required to achieve climate stabilization, acknowledging possible trade-offs between short- and long-term emissions reduction objectives. A strong focus on short-term carbon balances may result in decisions that make long-term climate objectives more difficult to meet.» IEA states that « the current rate of bioenergy deployment is well below the levels required in low carbon scenarios. Accelerated deployment is urgently needed to ramp up the contribution of sustainable bioenergy across all sectors » They recommend a five-fold increase in sustainable bioenergy feedstock supply. The National Association of University Forest Resources Programs agrees, and argues that a timeframe of 100 years is recommended in order to produce a realistic assessment of cumulative emissions: «Comparisons between forest biomass emissions and fossil fuel emissions at the time of combustion and for short periods thereafter do not account for long term carbon accumulation in the atmosphere and can significantly distort or ignore comparative carbon impacts over time. The most common timeframe for measuring the impacts of greenhouse gases is 100 years, as illustrated by the widespread use of 100-year global warming potentials. This timeframe provides a more accurate accounting of cumulative emissions than shorter intervals.»


Carbon neutrality for energy crops

Like with forests, it is the total amount of CO2 equivalent emissions and absorption together that determines if an energy crop project is carbon positive, carbon neutral or carbon negative. If emissions during agriculture, processing, transport and combustion are higher than what is absorbed, both above and below ground during crop growth, the project is carbon positive. Likewise, if total absorption over time is higher than total emissions, the project is carbon negative. Many first generation biomass projects are carbon positive (have a positive GHG life cycle cost), especially if emissions caused by direct or indirect land use change are included in the GHG cost calculation. The IPCC state that indirect land use change effects are highly uncertain, though. Some projects have higher total GHG emissions than some fossil based alternatives. Transport fuels might be worse than solid fuels in this regard. During plant growth, ranging from a few months to decades, CO2 is re-absorbed by new plants. While regular forest stands have carbon rotation times spanning many decades, short rotation forestry (SRF) stands have a rotation time of 8–20 years, and short rotation coppicing (SRC) stands 2–4 years. Perennial grasses like
miscanthus ''Miscanthus'', or silvergrass, is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ...

miscanthus
or napier grass have a rotation time of 4–12 months. In addition to absorbing CO2 and storing it as carbon in its above-ground tissue, biomass crops also
sequester carbon
sequester carbon
below ground, in roots and soil. 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 Tillage is the agricultural Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary ...
procedures (plowing, digging) associated with growing annual crops. Tilling helps the soil
microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
populations to
decompose Decomposition is the process by which dead organic substance , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds com ...
the available carbon, producing CO2. Soil organic carbon has been observed to be greater below
switchgrass ''Panicum virgatum'', commonly known as switchgrass, is a perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a ...

switchgrass
crops than under cultivated cropland, especially at depths below . A large meta-study of 138 individual studies, done by Harris et al., revealed that second generation perennial grasses (miscanthus and switchgrass) planted on arable land on average store five times more carbon in the ground than short rotation coppice or short rotation forestry plantations (poplar and willow). McCalmont et al. compared a number of individual European reports on Miscanthus x giganteus carbon sequestration, and found accumulation rates ranging from 0.42 to 3.8 tonnes per hectare per year, with a mean accumulation rate of 1.84 tonne (0.74 tonnes per acre per year), or 25% of total harvested carbon per year. When used as fuel, greenhouse gas (GHG) savings are large—even without considering the GHG effect of carbon sequestration, miscanthus fuel has a GHG cost of 0.4–1.6 grams CO2-equivalents per megajoule, compared to 33 grams for coal, 22 for liquefied natural gas, 16 for North Sea gas, and 4 for wood chips imported to Britain from the USA. Likewise, Whitaker et al. argue that a
miscanthus ''Miscanthus'', or silvergrass, is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ...

miscanthus
crop with a yield of 10 tonnes per hectare per year sequesters so much carbon below ground that the crop more than compensates for both agriculture, processing and transport emissions. The chart on the right displays two CO2 negative miscanthus production pathways, and two CO2 positive poplar production pathways, represented in gram CO2-equivalents per megajoule. The bars are sequential and move up and down as atmospheric CO2 is estimated to increase and decrease. The grey/blue bars represent agriculture, processing and transport related emissions, the green bars represents soil carbon change, and the yellow diamonds represent total final emissions. Successful sequestration is dependent on planting sites, as the best soils for sequestration are those that are currently low in carbon. The varied results displayed in the graph highlights this fact. For the UK, successful sequestration is expected for arable land over most of England and Wales, with unsuccessful sequestration expected in parts of Scotland, due to already carbon rich soils (existing woodland) plus lower yields. Soils already rich in carbon includes
peatland , one of the largest fens in Estonia. A mire, peatland or quagmire is a wetland A wetland is a distinct ecosystem An ecosystem is a community (ecology), community of living organisms in conjunction with the nonliving components of thei ...

peatland
and mature forest. Milner et al. further argue that the most successful carbon sequestration in the UK takes place below improved
grassland Grasslands are areas where the vegetation Vegetation is an assemblage of species and the they provide. It is a general term, without specific reference to particular , life forms, structure, extent, or any other specific or geographic ...

grassland
. However, Harris et al. notes that since the carbon content of grasslands vary considerably, so does the success rate of land use changes from grasslands to perennial. The bottom graphic displays the estimated yield necessary to achieve CO2 negativity for different levels of existing soil carbon saturation. The higher the yield, the more likely CO2 negativity becomes.


Environmental impact


Biodiversity and pollution

Gasparatos et al. reviews current research about the side effects of all kinds of renewable energy production, and argue that in general there is a conflict between " ..site/local-specific conservation goals and national energy policy/climate change mitigation priorities .." The authors argue that for instance biodiversity should be seen as an equally " ..legitimate goal of the Green Economy as curbing GHG emissions." Oil palm and sugar cane are examples of crops that have been linked to reduced biodiversity. Other problems are pollution of soil and water from fertiliser/pesticide use, and emission of ambient air pollutants, mainly from open field burning of residues. The authors note that the extent of the environmental impact " ..varies considerably between different biomass energy options." For impact mitigation, they recommend " ..adopting environmentally-friendly bioenergy production practices, for instance limiting the expansion of monoculture plantations, adopting wildlife-friendly production practices, installing pollution control mechanisms, and undertaking continuous landscape monitoring." They also recommend " ..multi-functional bioenergy landscapes." Other measures include " ..careful feedstock selection, as different feedstocks can have radically different environmental trade-offs. For example, US studies have demonstrated that 2nd generation feedstocks grown in unfertilized land could provide benefits to biodiversity when compared to monocultural annual crops such as maize and soy that make extensive use of agrochemicals."
Miscanthus ''Miscanthus'', or silvergrass, is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ...
and
switchgrass ''Panicum virgatum'', commonly known as switchgrass, is a perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a ...

switchgrass
are examples of such crops.


Air quality

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. According to the IPCC, there is strong evidence that modern bioenergy have «large positive impacts» on air quality. When combusted in industrial facilities, most of the pollutants originating from woody biomass reduce by 97-99%, compared to open burning. A study of the giant brown haze that periodically covers large areas in South Asia determined that two thirds of it had been principally produced by residential cooking and agricultural burning, and one third by fossil-fuel burning.


Consequences of low surface power production density

While bioenergy is generally agreed to have a net reducing impact on greenhouse gas emissions on the global scale, increasing biomass demand can create significant social and environmental pressure in locations where the biomass is produced. The impact is primarily related to the low
surface power densityIn physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through Spac ...
of biomass (see below). The low surface power density has the effect that much larger land areas are needed in order to produce the same amount of energy, compared to for instance fossil fuels. As high-income European countries usually do not have sufficient local supply of biomass, large amounts are imported from lower-income countries. In some cases, large areas of natural forests are logged illegally (e.g. in Romania and Siberia), causing primary damage as a result of the removal of trees, and then secondary damage when remaining forest is put on fire to cover up illegal operations. Plans to remove trees and bushes from over 30 million hectares contracted for German power plants caused protests of environmental organisations in Namibia. In Mississippi a company producing wood pellets for UK power plants was fined $2.5m for exceeding
volatile organic compounds Volatile organic compounds (VOC) are organic chemicals , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's abilit ...
pollution for a number of years. Long-distance transport of biomass, often over thousands of kilometres on land or sea, is also criticised as wasteful and unsustainable.


Biomass surface power production densities compared to other renewables

To calculate land use requirements for different kinds of power production, it is essential to know the relevant surface power production densities.
Vaclav Smil Václav Smil (; born 9 December 1943) is a Czech-Canadian scientist and policy analyst. He is Distinguished Professor Emeritus in the Faculty of Environmental science, Environment at the University of Manitoba in Winnipeg, Manitoba, Canada. His int ...
estimates that the average lifecycle surface power densities for biomass, wind, hydro and solar power production are 0.30 W/m2, 1 W/m2, 3 W/m2 and 5 W/m2, respectively (power in the form of heat for biomass, and electricity for wind, hydro and solar). Lifecycle surface power density includes land used by all supporting infrastructure, manufacturing, mining/harvesting and decommissioning. Van Zalk et al. estimates 0.08 W/m2 for biomass, 0.14 W/m2 for hydro, 1.84 W/m2 for wind, and 6.63 W/m2 for solar (
median In statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data Data (; ) are individual facts, statistics, or items of information, often numeric. In a m ...

median
values, with none of the renewable sources exceeding 10 W/m2).
Fossil gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carb ...

Fossil gas
has the highest surface density at 482 W/m2 while
nuclear power Nuclear power is the use of nuclear reaction In nuclear physics Nuclear physics is the field of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), ...

nuclear power
at 240 W/m2 is the only high-density ''and''
low-carbon A low-carbon economy (LCE) or decarbonised economy is an economy An economy (; ) is an area of the production Production may be: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in t ...
energy source. The average human power consumption on ice-free land is 0.125 W/m2 (heat and electricity combined), although rising to 20 W/m2 in urban and industrial areas. Plants with low yields have lower surface power density compared to plants with high yields. Additionally, when the plants are only partially utilized, surface density drops even lower. This is the case when producing liquid fuels. For instance, ethanol is often made from sugarcane's sugar content or corn's starch content, while biodiesel is often made from rapeseed and soybean's oil content. Smil estimates the following densities for liquid fuels:Ethanol * Winter
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
(USA) 0.08 W/m2 *
Corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of the Americas, indige ...

Corn
0.26 W/m2 (yield 10 t/ha) *
Wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

Wheat
(Germany) 0.30 W/m2 * ''
Miscanthus x giganteus
Miscanthus x giganteus
'' 0.40 W/m2 (yield 15 t/ha) *
Sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, ...

Sugarcane
0.50 W/m2 (yield 80 t/ha wet) Jet fuel *
Soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume A legume () is a plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation ...
0.06 W/m2 *
Jathropa
Jathropa
(marginal land) 0.20 W/m2 *
Palm oil Palm oil is an edible vegetable oil Vegetable oils, or vegetable fats, are oil An oil is any nonpolar chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substa ...

Palm oil
0.65 W/m2 Biodiesel *
Rapeseed Rapeseed (''Brassica napus ''subsp.'' napus''), also known as rape, or oilseed rape, is a bright-yellow flowering member of the family Brassicaceae Brassicaceae () or Cruciferae () is a medium-sized and economically important family ...

Rapeseed
0.12 W/m2 (EU average) *
Rapeseed Rapeseed (''Brassica napus ''subsp.'' napus''), also known as rape, or oilseed rape, is a bright-yellow flowering member of the family Brassicaceae Brassicaceae () or Cruciferae () is a medium-sized and economically important family ...

Rapeseed
(adjusted for energy input, the Netherlands) 0.08 W/m2 *
Sugar beets A sugar beet is a plant whose root contains a high concentration of sucrose and which is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together wit ...
(adjusted for energy input, Spain) 0.02 W/m2 Combusting ''solid'' biomass is more energy efficient than combusting liquids, as the whole plant is utilized. For instance, corn plantations producing solid biomass for combustion generate more than double the amount of power per square metre compared to corn plantations producing for ethanol, when the yield is the same: 10 t/ha generates 0.60 W/m2 and 0.26 W/m2 respectively. Oven dry biomass in general, including wood, miscanthus and napier grass, have a calorific content of roughly 18 GJ/t. When calculating power production per square metre, every t/ha of dry biomass yield increases a plantation's power production by 0.06 W/m2. Consequently, Smil estimates the following: * Large-scale plantations with
pines
pines
,
acacias ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia, but it has no ...

acacias
,
poplars ''Populus'' is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood. The weste ...

poplars
and
willows Willows, also called sallows and osiers, from the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining ( ...

willows
in temperate regions 0.30–0.90 W/m2 (yield 5–15 t/ha) * Large scale plantations with
eucalyptus ''Eucalyptus'' () is a of over seven hundred species of s, shrubs or in the , Myrtaceae. Along with several other genera in the , including ', they are commonly known as s. Plants in the genus ''Eucalyptus'' have bark that is either smooth, ...

eucalyptus
,
acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of nam ...

acacia
,
leucaena ''Leucaena'' is a genus of flowering plants in the Mimosoideae, mimosoid clade of the subfamily Caesalpinioideae of the legume family Fabaceae. It contains about 24 species of trees and shrubs, which are commonly known as leadtrees. They are nativ ...
,
pinus A pine is any conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The divi ...

pinus
and
dalbergia ''Dalbergia'' is a large genus of small to medium-size trees, shrubs and lianas in the pea family, Fabaceae, subfamily Faboideae. It was recently assigned to the informal monophyly, monophyletic ''Dalbergia'' clade (or tribe): the Dalbergie ...
in tropical and subtropical regions 1.20–1.50 W/m2 (yield 20–25 t/ha) In Brazil, the average yield for eucalyptus is 21 t/ha (1.26 W/m2), but in Africa, India and Southeast Asia, typical eucalyptus yields are below 10 t/ha (0.6 W/m2). FAO (Food and Agriculture Organization of the United Nations) estimate that forest plantation yields range from 1 to 25 m3 per hectare per year globally, equivalent to 0.02–0.7 W/m2 (0.4–12.2 t/ha): *
Pine A pine is any conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The div ...

Pine
(Russia) 0.02–0.1 W/m2 (0.4–2 t/ha or 1–5 m3) *
Eucalyptus ''Eucalyptus'' () is a of over seven hundred species of s, shrubs or in the , Myrtaceae. Along with several other genera in the , including ', they are commonly known as s. Plants in the genus ''Eucalyptus'' have bark that is either smooth, ...

Eucalyptus
(Argentina, Brazil, Chile and Uruguay) 0.5–0.7 W/m2 (7.8–12.2 t/ha or 25 m3) *
Poplar
Poplar
(France, Italy) 0.2–0.5 W/m2 (2.7–8.4 t/ha or 25 m3) Smil estimate that natural temperate mixed forests yield on average 1.5–2 dry tonnes per hectare (2–2,5 m3, equivalent to 0.1 W/m2), ranging from 0.9 m3 in Greece to 6 m3 in France). IPCC provides average net annual biomass ''growth'' data for natural forests globally. Net growth varies between 0.1 and 9.3 dry tonnes per hectare per year, with most natural forests producing between 1 and 4 tonnes, and with the global average at 2.3 tonnes. Average net growth for plantation forests varies between 0.4 and 25 tonnes, with most plantations producing between 5 and 15 tonnes, and with the global average at 9.1 tonnes. As mentioned above, Smil estimates that the world average for wind, hydro and solar power production is 1 W/m2, 3 W/m2 and 5 W/m2 respectively. In order to match these surface power densities, plantation yields must reach 17 t/ha, 50 t/ha and 83 t/ha for wind, hydro and solar respectively. This seems achievable for the tropical plantations mentioned above (yield 20–25 t/ha) and for elephant grasses, e.g.
miscanthus ''Miscanthus'', or silvergrass, is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term ...

miscanthus
(10–40 t/ha), and
napier
napier
(15–80 t/ha), but unlikely for forest and many other types of biomass crops. To match the world average for biofuels (0.3 W/m2), plantations need to produce 5 tonnes of dry mass per hectare per year. When instead using the Van Zalk estimates for hydro, wind and solar (0.14, 1.84, and 6.63 W/m2 respectively), plantation yields must reach 2 t/ha, 31 t/ha and 111 t/ha in order to compete. Only the first two of those yields seem achievable, however. Yields need to be adjusted to compensate for the amount of moisture in the biomass (evaporating moisture in order to reach the ignition point is usually wasted energy). The moisture of biomass straw or bales varies with the surrounding air humidity and eventual pre-drying measures, while pellets have a standardized (ISO-defined) moisture content of below 10% (wood pellets) and below 15% (other pellets). Likewise, for wind, hydro and solar, power line transmission losses amounts to roughly 8% globally and should be accounted for. If biomass is to be utilized for electricity production rather than heat production, note that yields has to be roughly tripled in order to compete with wind, hydro and solar, as the current heat to electricity conversion efficiency is only 30–40%. When simply comparing surface power density without regard for cost, this low heat to electricity conversion efficiency effectively pushes at least solar parks out of reach of even the highest yielding biomass plantations, surface power density wise.


See also

*
Biochar Biochar is charcoal or soil, and firing it (circa 1890) Charcoal is a lightweight black carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and t ...

Biochar
*
Biofact (biology) In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, D ...
*
Biomass (ecology) The biomass is the mass of living biological organisms in a given area or ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic compo ...
*
Gasification Gasification is a process that converts biomass Biomass is plant or animal material used as fuel to produce electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Stati ...

Gasification
* Biomass heating system *
Biomass to liquidBiomass to liquid (BtL or BMtL) is a multi-step process of producing synthetic hydrocarbon In organic chemistry, a hydrocarbon is an organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally an ...
*
BioproductsBioproducts or bio-based products are Raw material, materials, chemicals and energy derived from renewable biological resources. Bioresources Biological resources include agriculture, forestry, and biologically-derived waste, and there are many othe ...
*
Biorefinery A biorefinery is a refinery A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value. Types of refineries Diffe ...

Biorefinery
* European Biomass Association *
Carbon footprint A carbon footprint is the total greenhouse gas (GHG) emissions caused by an individual, event, organization, service, place or product, expressed as carbon dioxide equivalent Global warming potential (GWP) is the heat absorbed by any greenhou ...

Carbon footprint
*
Cow dung Cow dung, also known as cow pats, cow pies or cow manure, is the waste product (faeces Feces (American and British English spelling differences#ae and oe, or faeces) is the solid or semi-solid remains of food that was not digested in t ...
* Energy forestry *
Firewood Firewood is any wooden Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branche ...

Firewood
*
Microgeneration Microgeneration is the small-scale generation of heat and electric power Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt The watt (symbol: W) ...
*
Microbial electrolysis cell
Microbial electrolysis cell
generates hydrogen or methane * Permaculture * Thermal mass * Woodchips * Renewable Energy Transition


Notes


References


Sources

* * * * * * * * * * * } * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


External links


Biomass interactive by PBL Netherlands Environmental Assessment Agency

Forest, Nature and Biomass
* * {{Authority control Biomass, Renewable energy Bioenergy Alternative energy