The objective of this study is to evaluate the environmental impact of the entire production chain of fuels made from biomass used in Switzerland. Firstly the study supplies an analysis of the possible environmental impacts of biofuels suitable as a basis for political decisions. Secondly an “environmental life-cycle analysis“ (LCA) of the various biofuels is done, which can be used as a basis for granting an exemption from the excise duty on hydrocarbon oil. In addition, the impacts of fuel use are compared with other uses for bioenergy such as the generation of electricity and heat. The study based on the Swiss database of environmental inventories ecoinvent gives a holistic comparison of the environmental impacts of biofuels; however neither the costs of biofuels nor the social consequences of their production are evaluated. The results refer to average values from the year 2004 in the respective production countries and are to be taken as a snapshot of factors relevant to the fuels’ use in Switzerland. Thus the study cannot provide any answers to questions concerning future impacts – for instance, on food prices. In principle, each of the fuels examined (bioethanol, biomethanol, biodiesel and biogas) can be produced in an environmentally friendly way – it depends on what raw materials and production technologies are used. Most of the environmental impacts can be attributed to the agricultural cultivation of the respective raw materials (feedstocks). The environmental impact from fuel processing is usually much lower. The environmental impact from the transport from the production site to Swiss filling stations is even less, even when the biofuels are produced overseas. The present study shows that with most biofuels there is a trade-off between minimizing greenhouse gases (GHG emissions) and a positive environmental LCA. It is true that GHG emissions can be reduced by more than 30% with a number of biofuels. However most of these supply paths show greater impacts than petrol for various other environmental indicators. The environmental LCA was done using two different methods: one was the Swiss method of ecological scarcity (Environmental Impact Points, UBP 06), which evaluates the difference between environmental impacts and legal limits. The other one is the European Eco-indicator 99 method, which quantifies the damage done to human health and ecosystems. Both methods show the same results: in the case of tropical agriculture it is primarily the slashing and burning of rainforests that releases the largest quantities of CO2, causes an in-crease in air pollution and has massive impacts on biodiversity. In the moderate latitudes it is partly the lower crop yields, partly the intensive fertilizer use and mechanical tilling of the soil that are the causes of a bad environmental evaluation. However unlike the case of fossil fuels, the environmental impacts of biofuels can be greatly reduced by specific measures. The study shows in sensitivity analysis how, for instance, a reduction in methane leakage can improve the LCA of biogas production or what effect a prohibition of slash and burn would have on the LCA of biodiesel made from palm oil. Overall, the results of the study show that any promoting of biofuels by a tax break, for instance, must be done so as to target the best production paths. Not all biofuels per se can reduce environmental impacts as compared to fossil fuels. Currently, of all the production paths investigated, it is especially the use of biogenic wastes ranging from grass to wood that brings a reduction in environmental impact as compared with petrol. Since the potential of domestic bioenergy today is limited – and will be so in future – bioenergy will not solve our energy problems. However it if the available biomass is transformed into energy in an efficient and environmentally friendly manner, while at the same time consumption is reduced and energy efficiency in-creased, these alternative energy carriers can together with other forms of renewable energy play a role in our future energy supply that should not be neglected. Environmental assessment of biofuels, R. Zah et al., Empa