Uppgradering av biogas i systemperspektiv med avseende på miljöpåverkan och kostnader
Swedish biogas is currently produced mainly by anaerobic digestion of sewage sludgeat sewage treatment plants, landfills and anaerobic digestion of household or industrialwaste. Also cattle ma-nure from farms can be used to produce biogas. Upgradingbiogas represents an increase in methane concentration from about 65 % to about 97%. In addition, particles and contaminants must be sepa-rated from the upgradedbiogas. There are various methods for upgrading and this report compares sixdifferent methods with respect to environment and economy: water scrubber,Biosling, cryo technology, chemical absorption, Pressure Swing Adsorption (PSA) andmembrane separation.According to the used ORWARE model, chemical adsorption with amine has the leastenvironmen-tal impact (methane emissions) and the lowest costs. The chemical usedin the method is very good at reducing CO2 and chemical adsorption gives anupgraded gas containing around 99 % methane. The downside of amine is that itcontributes to the acidification of the environment and additional heat is needed tofree the CO2. It is also a small scale method. PSA and membrane separation shall beavoided when it comes to environmental impacts. When it comes to the economy, itis more dif-ficult to compare the methods. The reason is that the scale does mattertogether with factors such as geography. The methods are also improving andmodernizing. It is important to consider this and be up to date when investing in anew biogas upgrading plant.