An evaluation of drawbacks or benefits of renewable vehichle gas must start with the feedstock. Biofuels for transport must fulfill the sustainability criteria in the EU renewable energy directive, where at the moment fuels produced from biomass originating from farm land is strongly debated and the criteria are under revision. We consider it problematic if all crops from farm land are treated equally, irrespective of environmental effects or impact on the cultivation systems. The aim of this project is to establish facts to contribute to the debate about energy crops on farm land, and here with focus on grass-clover ley crops for biogas production. This because the climate impact of ley in a crop rotation is fundamentally different from the impact of increased cereal or rape seed production for biofuel purposes. The project includes an analysis of sustainability aspects like climate effects, land use and economical aspects, both for the farmer and for the biofuel producer.