Bioenergy

Bioenergy is energy recovered from recently living organic matter: wood, agricultural residues, energy crops, manure, sewage sludge, food waste and the biogenic share of municipal waste. It is the oldest fuel people use and still the largest renewable source of heat, yet in electricity it is a niche. In 2025 bioenergy produced roughly 710 TWh, about 2.2% of world electricity, compared with 8–9% each for solar and wind. What sets it apart from those two is that it is dispatchable, can be stored as a fuel and can be turned into liquid and gaseous fuels. That explains both its appeal and how heated the debate around it gets.

How it works

Every bioenergy route releases chemical energy that plants captured from sunlight through photosynthesis. Three families of conversion dominate:

• Thermochemical. Burning solid biomass in a boiler raises steam for a turbine, just as in a coal plant. Gasification (partial oxidation at 700–1,000 °C) makes a syngas of CO and H2. Pyrolysis, carried out without oxygen, yields bio-oil, gas and char.
• Biochemical. In anaerobic digestion, microbes break down wet organic matter without oxygen and produce biogas. Fermentation turns sugars and starches into ethanol.
• Chemical. Transesterification converts vegetable oils and animal fats into biodiesel (FAME). Hydrotreating produces hydrotreated vegetable oil (HVO) and much of today’s sustainable aviation fuel.

Energy content depends heavily on the feedstock and, above all, on moisture. Oven-dry wood has a lower heating value near 18–19 MJ/kg and wood pellets about 17 MJ/kg (4.7–4.8 kWh/kg) at 6–10% moisture, while freshly felled wood manages barely 8–10 MJ/kg. Our fuel energy content calculator converts between these and fossil equivalents.

Main variants

Solid biomass combustion and co-firing

Dedicated biomass plants run from 1–50 MW district-heating boilers burning wood chips up to pulverised-fuel units of several hundred megawatts. The best-known is Drax in the UK. Between 2013 and 2018 it converted four 645 MW coal units to wood pellets, and it now burns several million tonnes of pellets a year, shipped mainly from the south-eastern United States and Canada. Co-firing mixes 5–20% biomass into a coal boiler with modest modifications. It used to be common in Europe and is now widespread in Japan and South Korea.

Combined heat and power (CHP) gets the most out of solid biomass. Nordic plants sell both electricity and district heating and reach total efficiencies of 85–90%.

Biogas and biomethane

Biogas plants digest manure, slurry, crop residues, energy crops (maize silage in Germany above all), sewage sludge or food waste at 35–55 °C. The gas is 50–75% methane and mostly CO2 otherwise. It is either burnt on site in a gas engine (CHP) or upgraded to biomethane using membranes, water scrubbing or amine absorption and fed into the gas grid. Europe has the largest fleet, around 20,000 plants, led by Germany, Italy, France and Denmark. In Denmark, biomethane already covers a large share of grid gas demand. The leftover digestate makes a valuable fertiliser. The biogas calculator estimates gas and power yields for specific feedstocks.

Indicative ranges compiled from European anaerobic-digestion guidance (e.g. KTBL, FNR); real yields depend on dry-matter content and retention time.

Waste-to-energy

Municipal solid waste incinerators with energy recovery burn residual waste on moving grates. Corrosive flue gases limit steam conditions, so electrical efficiency is modest (typically 20–30%), but CHP versions reach 80% or more overall. Only the biogenic fraction counts as renewable, typically around half of the energy in mixed MSW. The plastic fraction is fossil. Landfill gas capture is the low-tech relative: it recovers methane that would otherwise escape.

Liquid biofuels

Ethanol (from US corn and Brazilian sugarcane) and biodiesel/HVO (from rapeseed, soy, palm oil and waste oils) supply roughly 3–4% of global transport energy (IEA). The US and Brazil make most of the world’s ethanol, and Indonesia’s palm-based biodiesel mandate is the largest of its kind. Advanced, cellulosic and waste-based fuels are growing mainly because of aviation-fuel mandates such as the EU’s ReFuelEU.

BECCS

Bioenergy with carbon capture and storage is the variant that climate models cite most. Ethanol fermentation gives off an almost pure CO2 stream, so capture is cheap there. The ADM plant in Decatur, Illinois has injected CO2 into a saline aquifer since 2017. Post-combustion capture on biomass power and CHP plants, planned at Drax and under construction at Stockholm Exergi, costs far more. How much CO2 is actually removed depends entirely on supply-chain emissions and on how the feedstock’s carbon is accounted for.

Efficiency and capacity factor

Fuel can be stockpiled, so biomass and biogas plants with a secure supply run at high capacity factors: 80–90% for biogas CHP engines and dedicated biomass plants. Plants that follow heat demand or the merit order often run less. IRENA’s cost database shows a global weighted-average capacity factor for new bioenergy projects in the 60–80% band in recent years.

The capacity factor calculator converts between installed capacity and annual output.

Costs

Unlike most renewables, bioenergy’s cost is often dominated by fuel rather than capital. Feedstock can be free or even earn a gate fee (waste, manure), or it can cost USD 3–10/GJ or more (pellets, energy crops). IRENA’s Renewable Power Generation Costs in 2023 reports a global weighted-average LCOE of about USD 0.07/kWh for newly commissioned bioenergy plants. Individual projects range from below USD 0.05/kWh (bagasse and residues in Brazil and India) to above USD 0.20/kWh (small European plants burning purchased fuel). Installed costs run roughly USD 1,000–4,000/kW for solid-biomass plants and USD 2,500–6,000/kW for small European biogas plants.

In most markets that makes bioenergy dearer than new utility-scale solar or onshore wind. It competes where it burns residues already collected at a mill, or where heat sales and waste-disposal fees prop up the business case. Biomethane production in Europe typically costs EUR 50–110/MWh (IEA 2020): well above historical natural gas prices, but below the 2022 peaks. Test your own assumptions with the LCOE calculator.

Land, water and materials

Land is the hard limit. Over a year, photosynthesis stores well under 1% of incoming sunlight as chemical energy, so energy crops deliver around 0.1–0.6 W per square metre of land, one to two orders of magnitude less than solar PV. Producing 1 TWh of electricity a year from dedicated energy crops takes on the order of 500–1,500 km² of farmland; ground-mounted PV needs roughly 10–20 km². For this reason most analysts, the IEA and IPCC among them, tie bioenergy’s sustainable role to residues and wastes (forestry by-products, sawdust, straw, manure, used cooking oil) rather than to big new plantations that compete with food or drive deforestation.

The conversion step uses a moderate amount of water (steam plants need cooling, like coal), but irrigated energy crops can use a great deal. Material needs are low compared with other technologies: ordinary steel boilers, turbines and engines, with none of the critical minerals that go into batteries or permanent-magnet generators.

Lifecycle CO2 emissions

No generation technology has more contested lifecycle emissions than bioenergy, because the results hinge on assumptions about the biogenic carbon cycle. IPCC AR5 WGIII Annex III gives:

• Dedicated biomass power: 130–420 g CO2e/kWh, median 230 g
• Biomass co-firing with coal: 620–890 g CO2e/kWh, median 740 g (mostly from the coal share)

These figures assume regrowth offsets the stack CO2 from biomass, and they leave out indirect land-use change and albedo effects. Studies that include carbon debt, the time a harvested forest needs to re-absorb its carbon, find that pellets made from whole stemwood can emit more than coal over 20–50 years. Residues that would otherwise rot or be burnt in the open pay back within a few years. Biogas from manure can come out strongly negative because it prevents methane escaping from slurry storage; biogas from energy crops scores much worse.

Policy sets minimum thresholds instead of assuming neutrality. Under the EU’s RED II, electricity and heat from biomass installations that started operating from 2021 must cut GHG emissions by at least 70% against a fossil comparator, rising to 80% from 2026. Land criteria also exclude primary forest, peatland and high-biodiversity areas.

Safety and environmental impacts

• Air pollution. Small-scale wood burning is a leading source of fine particulates (PM2.5) in Europe, ahead of road traffic in many countries. Large plants with electrostatic precipitators and bag filters emit far less per unit of energy.
• Biodiversity. Clear-cutting for pellets and turning grassland or forest into energy cropland can damage habitats. Certification schemes (SBP, FSC, PEFC, ISCC) and the RED criteria try to screen this out.
• Methane slip. Methane has a high warming potential, so leaks from digesters, upgrading units and open digestate storage can eat into the climate benefit of biogas.
• Operational risks. Dust explosions in pellet silos, self-heating in stored chips and toxic H2S in digesters all call for careful handling.
• Food and fuel. Crop-based biofuels compete for arable land, and the 2007–2008 food price spike put mandates under fresh scrutiny.

Outlook

The IEA expects modern bioenergy to keep growing mostly in heat, industry and transport. In electricity it is up against ever-cheaper wind, solar and battery storage. Growth is strongest in biomethane (Europe’s REPowerEU target is 35 bcm per year by 2030), in aviation fuels pushed by blending mandates, and in Asian biomass power, especially co-firing in Japan and new residue-fired plants in India and Brazil. On grids with a high share of variable renewables, flexible biomass and biogas plants that run when wind and sun are scarce are worth more than baseload units.

BECCS is still the big unknown. Integrated assessment models often assume several gigatonnes of BECCS removals a year by mid-century, while real-world capture today amounts to single-digit million tonnes. Whether bioenergy lives up to that depends less on engineering than on credible sustainability rules, transparent carbon accounting and how much truly surplus biomass exists. For a side-by-side view against other options, see technology comparison, or find existing plants on the power plants map.