Energy from used water and sludge Heat recovered by heat pumps Pyrolysis Biogas from anaerobic processes Digester Upflow anaerobic sludge blanket reactor Hydrogen fuel cell Microbial fuel cell Types of gas Biogas 1 Household waste Biogas 2 Agrifood industry Natural gas Composition 60% CH 4 33 % CO 2 1% N 2 0% O 2 6% H 2 O 68% CH 4 26 % CO 2 1% N 2 0% O 2 5 % H 2 O 97.0% CH4 2.2% CO 2 0.4% N 2 0.4 % other Energy content kWh/m 3 6.17.511.3