BIOGAS

Biogas is a colourless gas that is insoluble in water, but due to the impurities it contains, it is highly corrosive. The most characteristic impurity in this mixture is hydrogen sulphide (H2S), which gives biogas its characteristic pungent “rotten egg” odour.

Biogas in landfills is generated by the anaerobic decomposition (in the absence of oxygen) of organic matter by bacteria. This process is continuous, both during the disposal of municipal waste and after the cell is sealed, as the lower layers of waste will always be partially protected from the outside environment in the first phase and then completely isolated when covered with soil and HDPE geomembrane.

How is it recovered?

ERSUC sells energy to the National Electricity Grid. Most of this energy is produced by the Integrated MSW Treatment and Recovery Plants, but also by the three already sealed Landfills.

The raw material for biogas production comes from MSW. In biological digestion, the organic fraction is delivered to the process after being diverted, first in Mechanical Treatment and then in Biological Treatment and in ERSUC's former Landfills (Aveiro – Taboeira, Coimbra – Taveiro and Figueira da Foz – Lavos) from the MSW deposited, but which have not received organic matter from MSW since 2012.

It is here in the landfills, where the amount of biogas produced declines due to the age of the RU, that there is a need to seek new, unexplored collection points by drilling new holes in new locations.

All improvements in the biogas production process bring economic, financial and environmental advantages, both through the production and sale of energy and through the reduction of methane emissions into the atmosphere, thus contributing to improving the environmental quality of the surrounding areas, since the components that cause unpleasant odours, particularly sulphur compounds, are extracted and destroyed during combustion, reducing the emission of the gases that have the greatest influence on the greenhouse effect.