Producing and using biogas through anaerobic digestion (AD) is a unique way of addressing multiple sustainability issues at the same time, including renewable energy production, waste management, climate change mitigation, and sustainable agriculture. Potential feedstocks for biogas include most wet organic wastes and by-products, such as animal manure, crop and other agricultural residues, household, commercial and industrial food waste, sewage sludge and industrial wastewater. AD technology enables improved sustainability performance of several sectors—including agriculture, wastewater and solid waste treatment of municipalities as well as industry—by capturing fugitive methane emissions and converting the energy potential in residues and wastes into useful forms of renewable energy. In addition, the co-products of AD can provide several positive effects. Digestate, the liquid or semi-solid residue of the input feedstock, holds the undegraded carbon and almost all of the nutrients from the feedstock, and can be used a soil amendment and fertilizer. When biogas is upgraded to biomethane, it is also possible to recover biogenic CO₂ as an additional co-product. Although not widely implemented so far, CO₂ from biogas has plenty of potential areas of use where it could replace fossil-based products in, for example, the food industry, chemical production and power-to-gas, further lowering the carbon footprint of AD. Last but not least, the energy rich biomethane can be used to replace fossil fuels in the energy and transport sectors reducing CO₂ and particulates emissions, or as a renewable feedstock for the chemical industry.

Renewable energy production from waste streams is generally considered to be the main purpose of AD, and therefore the capacity of AD plants is usually defined in terms of energy output or volume of biogas produced. Nevertheless, the co-products and other services provided by AD are key to its the overall economic and environmental sustainability performance.

Some highlights of the report:

China has the highest number of biogas plants among the reporting IEA Bioenergy Task 37 member countries, with more than 100,000 biogas plants, followed by Germany with over 10,000 and France with over 1,600 plants. Of the other reporting countries, Brazil has more than 800 biogas plants, UK has over 700 and the others have less than 500. With the exception of China, these are total numbers and include digesters of all sizes and technical configurations.Germany has the highest annual biogas production, around 87 TWh/y. China produces around 81 TWh per year, UK 32 TWh, France 25 TWh, Brazil 12 TWh and Denmark 7 TWh. The other reporting countries produce less than 3 TWh.The production systems differ between the reporting countries, both in terms of biogas plant types and upgrading plants. In Finland, Norway, Sweden, Switzerland and Canada, both wastewater treatment plants (WWTP) and plants based on mixed bio-waste play a more substantial role in biogas production than in other reporting countries. Agricultural plants constitute the majority of the biogas produced in China, Denmark, France and Germany. Landfilling of organic waste is being phased out in many countries, but landfill gas continues to be produced for many years and is the largest source of biogas in Brazil, Ireland and Canada.Regarding the upgrading of biogas to biomethane – where only half of the countries have reported recent data – membrane separation is the most common technology. With 364 upgraders, France also has the highest number of upgrading plants among the reporting countries.Use of biogas: Electricity and heat generation are the most common uses of biogas in Germany, Brazil, Canada, France and Finland. In Denmark and Switzerland, a large share of the produced biogas is upgraded into biomethane and injected into the gas grid. Sweden and Finland also have notable shares of biomethane production, but there it is mainly used as vehicle fuel, either as compressed (bio-CNG) or liquefied (bioLNG) gas. Industrial use is relatively common in France, Norway and Brazil.Policy frameworks and financial conditions for biogas production have developed in various directions as they are context-specific, that is, they depend on the country’s energy and industrial infrastructure and its objectives related to clean energy, climate change and waste management. Subsidizing electricity production from biogas through feed-in-tariffs has served as a common starting point in many European countries and North America, and is still the predominant support system in Brazil. Although biogas is used for heat, especially in WWTP and industrial biogas plants, only Ireland and France noted programs that support AD for heat production, and the UK has recently closed its Renewable Heat Incentive program. In recent years, in most European countries, Brazil and North America, the focus of biogas support has been shifting towards biomethane production for grid injection or for use as vehicle fuel. Sweden, Norway and Finland use tax exemptions for biogas use and investment support for new biogas plants as their main financial instruments. Many European countries have incentives for producing biogas from manure to mitigate agricultural methane emissions, and China has supported numerous AD demonstration projects for different types of manure.There is a lot of promising technical progress and innovation in the biogas sector, with projects from food grade CO₂ production to sustainable aviation fuel. In particular, there are many examples of projects aiming to exploit the biogas potential in lignocellulosic biomass, to increase the conversion of CO2 via methanation and power-to-gas, as well as projects that are investigating greater use of straw and intermediate crops in AD. Along with innovative system integration projects, these examples reflect growing momentum in this space, and increased societal relevance for the biogas sector in the future.