The primary treatment of biogas includes cooling, drying, and almost always remov­ing of hydrogen sulfide. More advanced applications of biogas require upgrading it to biomethane or removing carbon dioxide. The following methods are used for the removal of carbon dioxide from biogas: pressure swing absorption on zeolites, selective membrane separation, cryogenic separation, and biological or chemical fixation [104-106]. The typical technologies for biogas cleaning include scrubbing by solvents or an aqueous alkaline solution, absorption, and oxidation on solid sor­bents, chelation, precipitation in the form of poorly soluble metal sulfides, and bio­logical removal [105, 107, 108].

1.1.4 Biogas Utilization

The possible applications of biogas include:

• Heat or steam production via burning

• Electricity generation combined with heat and power production

• Usage as cooking gas instead of natural gas

• Usage as fuel for vehicles (upgrading to biomethane is necessary)

• Generation of electricity via fuel cells

• Production of chemicals