| Summary: | Swedish biogas is currently produced mainly by anaerobic digestion of sewage sludge at sewage treatment plants, landfills and anaerobic digestion of household or industrial waste. Also cattle ma-nure from farms can be used to produce biogas. Upgrading biogas represents an increase in methane concentration from about 65 % to about 97 %. In addition, particles and contaminants must be sepa-rated from the upgraded biogas. There are various methods for upgrading and this report compares six different methods with respect to environment and economy: water scrubber, Biosling, cryo technology, chemical absorption, Pressure Swing Adsorption (PSA) and membrane separation. According to the used ORWARE model, chemical adsorption with amine has the least environmen-tal impact (methane emissions) and the lowest costs. The chemical used in the method is very good at reducing CO2 and chemical adsorption gives an upgraded gas containing around 99 % methane. The downside of amine is that it contributes to the acidification of the environment and additional heat is needed to free the CO2. It is also a small scale method. PSA and membrane separation shall be avoided when it comes to environmental impacts. When it comes to the economy, it is more dif-ficult to compare the methods. The reason is that the scale does matter together with factors such as geography. The methods are also improving and modernizing. It is important to consider this and be up to date when investing in a new biogas upgrading plant.
|
|---|
