Biogas as vehicle fuel

There is growing interest in the use of biogas as a fuel for transport applications. Some of the drivers behind this are the increasing regulation and taxes on waste disposal, an increasing need for renewable fuel sources, the EC’s Biofuels Directive, the proposed Renewable Transport Fuel Obligation (RTFO), measures to improve local air quality and the need for clean transport fuels in urban areas. The aim of this paper is to present the potential role of biogas as a transport fuel. Biogas is produced from the process of anaerobic digestion of wet organic waste, such as cattle and pig slurries, food wastes and grown wet biomass. To be used as a transport fuel biogas has to be upgraded to at least 95% methane by volume and it can then be used in vehicles originally modified to operate on natural gas. Biogas fuelled vehicles can reduce CO2 emissions by between 75% and 200% compared with fossil fuels. The higher figure is for liquid manure as a feedstock and shows a negative carbon dioxide contribution which arises because liquid manure left untreated generates methane emissions, which are 21 times more powerful as a greenhouse gas than CO2. Hence there is a double benefit by reducing fossil emissions from burning diesel and reducing methane emissions from waste manure; Biogas will give lower exhaust emissions than fossil fuels, and so help to improve local air quality. The paper sets out the resource that is available for producing biogas, together with the basic details of production technology. It goes on to explore how this gas can be used in vehicles, describing the basic technology requirements. The energy data and the costs of producing on biogas as a transport fuel are presented