Overview
Biofuels are sources of renewable energy made from biomass, i.e. organic material from plants and animals, such as manure, wood, straw, hay and food waste. They can be processed and fuels can be made from them: biodiesel, bioethanol, biogas and wood fuels such as wood chips, wood briquettes and wood pellets.
Although organic material seems to be abundant in the world, biomass resources such as forests are limited. Forests play an important role in climate change adaptation and habitat preservation, which is why their economic use needs to be as efficient and sustainable as possible. Using remnants and waste generated in the forestry industry as wood fuel helps to minimise waste from valuable material.
In the Estonian context, biogas is another significant source of bioenergy besides wood fuels.
Biogas
Biogas is a renewable energy source consisting mainly of methane (CH4) and carbon dioxide (CO2). This gas is produced during the anaerobic decomposition of organic matter, which means that the decomposition takes place in an oxygen-free environment. Biogas occurs naturally in, for example, swamps and bogs and landfills, but it can also be produced under controlled conditions in biogas plants.
In biogas plants, special decomposition tanks or fermentation tanks are used for biogas production. The process takes place in several stages:
- Raw material collection: organic waste required for production, such as animal manure, food waste, agricultural waste and sewage sludge, are collected.
- Raw material processing: organic material is crushed and mixed to ensure uniform decomposition.
- Fermentation: the collected material is transferred to a fermentation tank where microorganisms break it down. This process takes place anaerobically, i.e. in an oxygen-free environment.
- Biogas release: methane and carbon dioxide are released during fermentation. This gas is collected and purified.
- Handling of residual products: the residual products of the fermentation process are liquid and solid digestate.
After purification, i.e. by separating hydrogen sulphide, CO2 and other impurities, biogas becomes biomethane. It is mainly used for electricity generation and heating. Biogas production can be easily regulated, making it a manageable type of energy alongside other types of renewable energy (solar and wind). Biomethane can also be used as a fuel for transport. The digestate or waste products generated during biogas production are good agricultural fertilisers.
How much biogas can be obtained from a certain amount of material depends on the content of organic matter and dry matter. For example, liquid cattle manure, used the most as we have sufficient livestock, yields 250–290 litres of biogas per kilogramme of organic matter. In experiments carried out at the University of Life Sciences, biomethane obtained from fish waste has been as much as 100 litres per kilogramme. Food waste can also produce 100 litres of biomethane per kilogramme of organic matter. The specific use of materials and their content in the raw material mix is the key to ensure an optimal production price.
Biogas has several advantages over fossil natural gas: biogas is obtained from renewable organic matter, which makes it much more sustainable and environmentally friendly and its production helps to reduce greenhouse gas emissions and supports the circular economy.
In Estonia, there are biogas plants all over the country, for example, in Ida-Viru County, Lääne-Viru County, Pärnu County, Järva County, Jõgeva County, Viljandi County, Tartu County and Harju County. Larger plants are usually located near agricultural companies or landfills with sufficient organic waste material. There is a high potential for biogas production in Estonia and we may see an increase in production volumes in the coming years.
RePowerEU
The project has been financed by the European Union's NextGenerationEU recovery funds. The page was compiled within the framework of REPowerEU, which aims to eliminate the European Union's dependence on Russian fossil fuels by saving energy, diversifying energy sources and accelerating the transition to clean energy.
