WP3.6 biogas as a vehicle fuel in commuter buses: Life cycle cost and green house gas study

Biofuels in the transport sector are believed to be capable of reducing the growth in carbon dioxide (CO₂) emissions. The European Union is strongly promoting biofuels, e.g. by an ambitious target of 10 % substitution of transport fuels by renewable energy by 2020. The aim of this master's thesis was to evaluate the costs and greenhouse gas emissions from the generation, distribution and usage of upgraded biogas in transportation buses. The costs were covered using life cycle cost analysis. The greenhouse gas emissions were based on the literature results of the Life Cycle Assessment analysis. The costs from commuter buses using biogas were compared to buses using diesel. The emissions from diesel and natural gas buses were compared, and the costs were expressed as a specific cost with units €c per driven kilometre (€c/km) and the greenhouse gas emissions as a specific emission with units of carbon dioxide equivalent grams per kilometre (g CO₂eq/km). A comparative cost estimate was made for the biogas generation capacity of 1 000 Nm3
/h raw gas. The results show that the costs of biogas generation for fuel filling
was about 49 €c/km. Respectively, the cost from diesel fuel was 45 €c/km. The
specific cost for a gas-powered bus was on average 70 €c/km and respectively for diesel 59 €c/km. The total cost of biogas use as a vehicle fuel was thus 14 % higher than diesel use. Cost calculations were updated from year 2010 to 2012 and during that time diesel price was increased 40 %. Results from update showed that diesel bus costs were placed to equal level with gas buses to 127 and 126 €c/km. The greenhouse gas emissions from biomethane production were strongly dependent on the used substrate. The driving time greenhouse gas emissions (tankto-wheel) from a biomethane powered bus were 0 g CO₂eq/km. Total savings of greenhouse gas emissions from biomethane made from manures is about 82 % and 73 % if made from municipal waste.