Environmental assessment of biogas co- or tri-generation units by life cycle analysis methodology

A life cycle analysis performed on biogas co- or tri-generation units shows that the environmental impact depends on the fraction of heat (or cold) used, the distance for crops collection, the efficiencies of the unit and on the NOx emissions. A high efficiency unit (ηel = 0.4 and ηg = 0.8) and low NOx content (80 mg/N m3) based on 20 km crops collection will save CO2 emissions and act in a CO2 sink resulting in one of the very few technologies capable of reducing atmospheric CO2 concentration.