Bioenergy is a type of

renewable energy Renewable energy (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...

that is derived from plants and animal waste. The

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

that is used as input materials consists of recently living (but now dead) organisms, mainly plants. Thus,

fossil fuels A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geologica ...

are not regarded as biomass under this definition. Types of biomass commonly used for bioenergy include wood, food crops such as corn, energy crops and waste from forests, yards, or farms. Bioenergy can help with

climate change mitigation Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include energy conservation, conserving energy and Fossil fuel phase-out, repl ...

but in some cases the required biomass production can increase

greenhouse gas emissions Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...

or lead to local

biodiversity loss Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in Biodiversity, b ...

. The environmental impacts of biomass production can be problematic, depending on how the biomass is produced and harvested. But it still produces CO2; so long as the energy is derived from breaking chemical bonds. The IEA's Net Zero by 2050 scenario calls for traditional bioenergy to be phased out by 2030, with modern bioenergy's share increasing from 6.6% in 2020 to 13.1% in 2030 and 18.7% in 2050. Bioenergy has a significant climate change mitigation potential if implemented correctly. Most of the recommended pathways to limit global warming include substantial contributions from bioenergy in 2050 (average at 200 EJ).

Definition and terminology

The

IPCC Sixth Assessment Report The Sixth Assessment Report (AR6) of the United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) is the sixth in a series of reports which assess the available scientific information on climate change. Three Working Groups (WGI, II, ...

defines ''bioenergy'' as "energy derived from any form of

or its metabolic by-products".IPCC, 2022
Annex I: Glossary
an Diemen, R., J.B.R. Matthews, V. Möller, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, A. Reisinger, S. Semenov (eds) In IPCC, 2022
Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.) Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.020 It goes on to define ''biomass'' in this context as "organic material excluding the material that is fossilised or embedded in geological formations". This means that

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

or other

is not a form of biomass in this context. The term ''traditional biomass'' for bioenergy means "the combustion of wood, charcoal, agricultural residues and/or animal dung for cooking or heating in open fires or in inefficient stoves as is common in low-income countries". Since biomass can also be used as a fuel directly (e.g. wood logs), the terms ''biomass'' and ''biofuel'' have sometimes been used interchangeably. However, the term ''biomass'' usually denotes the biological raw material the fuel is made of. The terms

biofuel Biofuel is a fuel that is produced over a short time span from Biomass (energy), biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil. Biofuel can be produced from plants or from agricu ...

biogas Biogas is a gaseous renewable energy source produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste, Wastewater treatment, wastewater, and food waste. Biogas is produced by anaerobic ...

are generally reserved for liquid or gaseous fuels respectively.

Input materials

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 Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

switchgrass ''Panicum virgatum'', commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55th parallel north, 55°N latitude in Canada southwards into the United States and Mexico. Switch ...

, miscanthus and

bamboo Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in th ...

. The main

waste Waste are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor Value (economics), economic value. A wast ...

feedstocks are wood waste, agricultural waste,

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. ...

, and manufacturing waste. Upgrading raw biomass to higher grade fuels can be achieved by different methods, broadly classified as thermal, chemical, or biochemical: Thermal conversion processes use heat as the dominant mechanism to upgrade biomass into a better and more practical fuel. The basic alternatives are torrefaction,

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

, and gasification, these are separated mainly by the extent to which the chemical reactions involved are allowed to proceed (mainly controlled by the availability of oxygen and conversion temperature). Many chemical conversions are based on established coal-based processes, such as the Fischer-Tropsch synthesis. Like coal, biomass can be converted into multiple commodity chemicals. 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 Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

, and

composting Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by Decomposition, decomposing plant and food waste, recycling organic materials, and man ...

Applications

Biomass for heating

Biofuel for transportation

Based on the source of biomass,

s are classified broadly into two major categories, depending if food crops are used or not: First-generation (or "conventional") biofuels are made from ''food'' sources grown on arable lands, such as

sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...

and

. Sugars present in this biomass are fermented to produce bioethanol, an alcohol fuel which serves as an additive to gasoline, or in 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 reactions. Fuel cells are different from most bat ...

to produce electricity. Bioethanol is made by

, mostly from

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

s produced in

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...

crops such as

corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...

, or sweet sorghum. Bioethanol is widely used in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Biodiesel Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats. The roots of bi ...

is produced from the oils in for instance rapeseed or sugar beets and is the most common biofuel in Europe. Second-generation biofuels (also called "advanced biofuels") utilize ''non-food''-based biomass sources such as

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

energy crops and agricultural residues/waste. The feedstock used to make the fuels either grow on arable land but are byproducts of the main crop, or they are grown on marginal land. Waste from industry, agriculture, forestry and households can also be used for second-generation biofuels, using e.g. anaerobic digestion to produce

, gasification to produce syngas or by direct combustion. Cellulosic biomass, derived from non-food sources, such as trees and grasses, is being developed as a feedstock for ethanol production, and biodiesel can be produced from left-over food products like vegetable oils and animal fats.

Production of liquid fuels

* Biomass to liquid * Bioconversion of biomass to mixed alcohol fuels

Comparison with other renewable energy types

Land requirement

The surface power production densities of a crop will determine how much land is required for production. 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. Another estimate puts the values at 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 The median of a set of numbers is the value separating the higher half from the lower half of a Sample (statistics), data sample, a statistical population, population, or a probability distribution. For a data set, it may be thought of as the “ ...

values, with none of the renewable sources exceeding 10 W/m²).

Related technologies

Bioenergy with carbon capture and storage (BECCS)

Carbon capture and storage technology can be used to capture emissions from bioenergy power plants. This process is known as bioenergy with carbon capture and storage (BECCS) and can result in net

carbon dioxide removal Carbon dioxide removal (CDR) is a process in which carbon dioxide () is removed from the atmosphere by deliberate human activities and durably stored in geological, terrestrial, or ocean reservoirs, or in products.IPCC, 2021:Annex VII: Glossar ...

from the atmosphere. However, BECCS can also result in net positive emissions depending on how the biomass material is grown, harvested, and transported. Deployment of BECCS at scales described in some climate change mitigation pathways would require converting large amounts of cropland.

Climate and sustainability aspects

Environmental impacts

Bioenergy can either mitigate (i.e. reduce) or increase

. Local environmental impacts can be problematic. For example, forests are sometimes cleared for the production of sugarcane-derived bioethanol, like in the case of a large-scale project in Indonesia in 2025. Biomass production can create significant social and environmental pressure in the locations where the biomass is produced. The impact is primarily related to the low surface power density of biomass. 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

. Long-distance transport of biomass have been criticised as wasteful and unsustainable, and there have been protests against forest biomass export in Sweden and Canada.

Scale and future trends

In 2020 bioenergy produced 58 EJ ( exajoules) of energy, compared to 172 EJ from

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

, 157 EJ from coal, 138 EJ from

natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...

, 29 EJ from nuclear, 16 EJ from

hydro Hydro (from ) may refer to: Energy technologies * Water-derived power or energy: ** Hydropower, derived from water ** Hydroelectricity, in electrical form * "Hydro", AC mains electricity in parts of Canada * Micro hydro, a type of hydroelect ...

and 15 EJ from

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

, solar and geothermal combined. Most of the global bioenergy is produced from forest resources.WBA (2019
GLOBAL BIOENERGY STATISTICS 2019
World Bioenergy Association Generally, bioenergy expansion fell by 50% in 2020. China and Europe are the only two regions that reported significant expansion in 2020, adding 2 GW and 1.2 GW of bioenergy capacity, respectively. 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.Brack, D. (2017)
Woody Biomass for Power and Heat Impacts on the Global Climate
Research Paper - Environment, Energy and Resources Department. 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."

By country

References

Sources

* * * * * * * * * * * * {{Authority control Biofuels