Bioenergy is a type of renewable energy made from plants and animals. The materials used for bioenergy come from recently living organisms that are now dead, mostly plants. Fossil fuels are not considered biomass in this context. Common types of biomass used for bioenergy include wood, food crops like corn, energy crops, and waste from forests, yards, or farms. Bioenergy can also refer to electricity created through the process of photosynthesis in living organisms, often using special cells that use microorganisms or devices that convert light into electricity using living organisms.
Bioenergy can help reduce climate change, but in some cases, producing the needed biomass may increase greenhouse gas emissions or harm local wildlife. The environmental effects of biomass production depend on how it is grown and collected. However, bioenergy still releases carbon dioxide because it involves breaking chemical bonds.
According to the IEA's Net Zero by 2050 plan, traditional bioenergy should be reduced by 2030, while modern bioenergy's share should grow from 6.6% in 2020 to 13.1% in 2030 and 18.7% in 2050. If used properly, bioenergy has the potential to significantly help reduce climate change. Most plans to limit global warming by 2050 include a large role for bioenergy, with an average contribution of 200 EJ.
Definition and terminology
The IPCC Sixth Assessment Report describes bioenergy as "energy created from any type of biomass or waste products from living things." In this context, biomass is defined as "organic material that is not fossilized or found in rocks deep underground." This means that coal and other fossil fuels are not considered biomass in this definition.
The term "traditional biomass for bioenergy" refers to "the burning of wood, charcoal, leftover plant materials, or animal waste for cooking or heating using open fires or simple stoves, which is common in countries with limited resources."
Biomass can sometimes be used directly as fuel, such as burning wood logs. Because of this, the terms "biomass" and "biofuel" are sometimes used as if they mean the same thing. However, "biomass" typically refers to the natural materials used to make fuel. The terms "biofuel" and "biogas" are usually used for liquid or gas fuels, respectively.
Input materials
Wood and leftover wood materials are the biggest source of biomass energy today. Wood can be used directly as fuel or turned into pellet fuel or other types of fuel. Other plants, such as corn, switchgrass, miscanthus, and bamboo, can also be used as fuel. The main types of waste used for energy include wood waste, agricultural waste, household trash, and waste from manufacturing. Improving raw biomass into better fuels can be done through three main methods: thermal, chemical, or biochemical.
Thermal methods use heat to change biomass into more useful fuel. The main types are torrefaction, pyrolysis, and gasification. These methods differ mainly based on how much oxygen is present and the temperature used during the process.
Many chemical methods use processes similar to those used for coal, such as the Fischer-Tropsch synthesis. Like coal, biomass can be changed into various types of chemicals.
Biochemical methods use natural processes to break down the materials in biomass. Microorganisms often help with this process. These methods include anaerobic digestion, fermentation, and composting.
Applications
Biomass heating systems use organic materials to create heat. These systems may use methods such as direct burning, gasification, combined heat and power (CHP), anaerobic digestion, or aerobic digestion to produce heat. Biomass heating systems can be fully automated, semi-automated, pellet-fired, or combined heat and power systems.
Biofuels are divided into two main categories based on the source of biomass:
First-generation (or "conventional") biofuels are made from food crops grown on farmland, such as sugarcane and maize. Sugars in these crops are fermented to create bioethanol, a type of alcohol fuel used as an additive to gasoline or in fuel cells to generate electricity. Bioethanol is produced mainly from carbohydrates found in crops like corn, sugarcane, or sweet sorghum. It is widely used in the United States and Brazil. Biodiesel is made from oils in plants such as rapeseed or sugar beets and is the most common biofuel in Europe.
Second-generation biofuels (also called "advanced biofuels") use non-food-based biomass sources, such as perennial energy crops, agricultural waste, or byproducts from farming. These materials may grow on farmland but are not the main crop, or they may grow on less productive land. Waste from industries, farming, forests, and homes can also be used to make second-generation biofuels. Methods include anaerobic digestion to produce biogas, gasification to create syngas, or direct burning. Cellulosic biomass, which comes from non-food sources like trees and grasses, is being developed as a material for ethanol production. Biodiesel can also be made from leftover food products such as vegetable oils and animal fats.
- Biomass to liquid
- Bioconversion of biomass to mixed alcohol fuels
Comparison with other renewable energy types
The amount of energy a crop can produce per unit of land area determines how much land is needed for energy production. On average, the energy production rates per unit of land for biomass, wind, hydro, and solar power are 0.30 watts per square meter, 1 watt per square meter, 3 watts per square meter, and 5 watts per square meter, respectively. For biomass, this energy is in the form of heat, while wind, hydro, and solar produce electricity. These rates include land used for all activities, such as building infrastructure, manufacturing, mining or harvesting resources, and removing equipment after use.
Another estimate shows different values: 0.08 watts per square meter for biomass, 0.14 watts per square meter for hydro, 1.84 watts per square meter for wind, and 6.63 watts per square meter for solar. These are median values, and none of the renewable energy sources exceed 10 watts per square meter.
Related technologies
Carbon capture and storage technology can be used to capture emissions from bioenergy power plants. This process is called bioenergy with carbon capture and storage (BECCS). It can help remove carbon dioxide from the atmosphere. However, sometimes BECCS may release more carbon dioxide than it captures, depending on how the plants used for bioenergy are grown, collected, and moved. Using BECCS on a large scale, as some climate change plans suggest, would require changing large areas of farmland for bioenergy production.
Bioenergy with carbon capture and storage (BECCS) involves using plants to create energy and capturing the carbon dioxide (CO₂) that is released during this process. Plants used for bioenergy can help reduce greenhouse gas emissions because when plants are harvested, new plants can grow to absorb CO₂ from the air through photosynthesis. After plants are collected, energy is created from them in forms like electricity, heat, or fuel through processes such as burning, chemical changes, or other methods. This process releases CO₂. In BECCS, some of the CO₂ is captured before it enters the air and stored underground using carbon capture and storage technology. Under certain conditions, BECCS can remove CO₂ from the atmosphere.
Studies suggest that BECCS could remove between 0 and 22 billion tons of CO₂ each year. As of 2024, there are three large-scale BECCS projects operating worldwide. However, using BECCS widely is limited by the cost of the technology and the availability of plants for energy. Since growing plants for energy uses a lot of land, using BECCS on a large scale could harm food production, human rights, and wildlife.
Climate and sustainability aspects
The climate effects of bioenergy depend on where biomass is grown and how it is managed. For example, burning wood releases carbon dioxide into the air. If trees are replanted in carefully managed forests after being cut down, the new trees can absorb carbon dioxide as they grow, which can balance the emissions. However, growing bioenergy crops may replace natural ecosystems, harm soil quality, and use water and chemical fertilizers.
About one-third of the wood used for heating and cooking in tropical regions is taken from forests in ways that harm the environment. Producing bioenergy often needs a lot of energy for harvesting, drying, and transporting biomass. These processes can release greenhouse gases. In some cases, changing how land is used, growing crops, and processing bioenergy can lead to more carbon emissions than using fossil fuels.
Using farmland to grow biomass can reduce the land available for growing food. In the United States, about 10% of motor gasoline is replaced by corn-based ethanol, which uses a large part of the corn harvest. In Malaysia and Indonesia, cutting down forests to grow palm oil for biodiesel has caused major problems for people and the environment. These forests are important for storing carbon and providing homes for many species. Since photosynthesis uses only a small part of the sun's energy, making a certain amount of bioenergy needs a lot of land compared to other renewable energy sources.
Environmental impacts
Bioenergy can either reduce or increase greenhouse gas emissions. Local environmental effects can cause problems. For example, forests are sometimes cleared to grow sugarcane for bioethanol, such as in a large project in Indonesia in 2025.
Biomass production can cause major social and environmental issues in the areas where it is grown. This is mainly because biomass has a low power density, meaning it requires much more land to produce the same amount of energy compared to fossil fuels.
Transporting biomass over long distances has been criticized as wasteful and not sustainable. Protests have occurred against the export of forest biomass in Sweden and Canada.
Scale and future trends
In 2020, bioenergy produced 58 EJ (exajoules) of energy. This is compared to 172 EJ from crude oil, 157 EJ from coal, 138 EJ from natural gas, 29 EJ from nuclear, 16 EJ from hydro, and 15 EJ from wind, solar, and geothermal combined. Most of the world’s bioenergy comes from forest resources.
Bioenergy expansion decreased by 50% in 2020. Only China and Europe reported significant growth, adding 2 GW and 1.2 GW of bioenergy capacity, respectively.
Most sawmill residue is already being used to make pellets, so there is little space for further expansion. For bioenergy to grow in the future, more pulpwood (tree thinnings) must be sent to pellet mills. However, harvesting pulpwood removes the chance for trees to grow older and store more carbon. Compared to pulpwood, sawmill residue has lower net emissions. Some types of biomass can be carbon-neutral over a few years, especially sawmill residue. These materials are waste from other forest operations and do not require additional harvesting. If not used, they would release carbon into the atmosphere anyway.