5 key aspects of biogas, the energy of the transition

By ENGIE - 20 May 2022 - 17:12

Biogas are produced by bacteria. Farmers play a crucial role in their production. A low-carbon energy that is supplied via a short channel and which helps promote the regions. Here are 5 things to know about biogas!


1. It takes approximately one month to produce biogas

Put animal or plant biomass (manure, slurry, crop residues, etc.) in an anaerobic digester. Heat to approximately 37-38 °C or to 50 °C, regularly stirring. After at least 30 days of fermentation, you are left with biogas on one end and digestate on the other. And all thanks to bacteria! 


2. Digestate is a remarkable fertiliser which can substitute its chemical counterparts.

On one end, biogas is recovered and used to produce heat, electricity and fuel for vehicles. When purified, the resulting product is called biomethane. Like natural gas, it is used for heating, cooking, powering industrial processes, etc. However, another valuable resource is produced during fermentation: digestate. This liquid residue full of undegraded organic matter and minerals is recovered by farmers. When spread on soil, it acts as a remarkable fertiliser that is easily assimilated by plants! And its carbon and environmental cost is well below that of mineral nitrogen and phosphorus fertilisers, which consume considerable amounts of fossil fuels during their production and import stages.


3. Biogas: an ideal energy source for the circular economy

Short channels represent a tremendous challenge for the energy transition. And, in this category, biogas excels! This is because agriculture is present in many countries and, as such, biomass is abundant. Anaerobic digesters can be installed next to farms, major organic matter suppliers (manure, slurry, straw, etc.), and agro-industrial waste units, thus limiting the transport of the biomass between the suppliers and the anaerobic digesters. The same goes for biogas/biomethane and the end consumer: towns and industrial zones next to an anaerobic digester can easily access its production (mains gas, bioNGV bus fleet). Conclusion: local applications and low carbon emissions. 


>> Also read Biomethane to support the energy transition: potential and cost in 2050 <<


4. Biogas production is good for the environment

Behind the short supply channel lie the environmentally-friendly arguments in favour of this energy. Firstly, the digester captures and transforms organic matter that releases greenhouse gases upon degradation. Secondly, the resulting biogas replaces higher-emission fossil energies, for a wide range of uses (heating, transport, electricity production, etc.)! Thirdly, by adding digestate to their soil, farmers can produce cover crops that store CO2 in the soil, producing a “carbon sink” effect!


5. Anaerobic digestion greatly reduces the odours of the organic matter used in biogas production

And the reason for this is simple! In the absence of oxygen, anaerobic digestion breaks down this organic matter. There is no air contact and therefore no odours. The volatile fatty acids responsible for the decomposition odours are destroyed. Many farmers use this process themselves to reduce the odours resulting from agricultural spreading of manure and slurry. Operators are required to minimise potential odours given off by this “brown gold” during the transport, storage, unloading and loading stages. For example: by working in closed buildings and by treating the air in farm buildings. 


Biogas can be used to:

  • Produce heat
  • Produce electricity
  • Produce heat and electricity in a combined manner (cogeneration)
  • Fuel vehicles (bioNGV for captive fleets, e.g. buses, collection fleets, etc.)
  • Replicate the uses of natural gas when in the form of biomethane (=purified biogas): heating, cooking, industrial processes, electricity production, bioNGV or bioLNG fuel.