Biogas exploitation by SOFC

Biogas as renewable source of energy is underexploited. We extrapolate the potential recoverable from waste streams in the EU-15 to 769 PJ (17.5 Mtoe), of which under 10% is used (1.7 Mtoe). SOFC can promote the valorisation of biogas in small CHP installations (10-500 kWel). An energy/exergy balance model was performed on a SOFC demonstration unit coupled to an existing farm biogas site. From 8.9 kW of biogas, the module was calculated to derive 3.4 kWel and 4.1 kW useful heat, achieving 38% electrical and 46% thermal, or 84% overall efficiency (HHV). The exergy yield was 45%, >4.5 kW being lost in heat exchange processes. Applying this result to the exploitation of 769 PJ biogas in SOFCs could generate yearly 82 TWhel and 8 Mtoe heat from 20 GWel installed power, corresponding to 3% of EU-15 electricity. Derived benefits would be CO2 emission reduction of >70 Mt/yr and fuel savings corresponding to 12% of the current natural gas import in Europe.