In its 2008 report "Future Bioenergy and Sustainable Land Use", the WBGU had advised against subsidising biofuels in developed countries, since this could not be justified from the point of view of sustainability. The WBGU recommended only promoting the use of bioenergy if this jeopardized neither food security nor the objectives of nature conservation and climate protection.
The global potential of bioenergy is limited because the land is also needed for food production and nature conservation. The WBGU estimates that up to 10% of world's energy needs could be sustainably met by bioenergy in the long term, preferably using biogenic waste products such as wood waste, liquid manure or straw.
In the WBGU's view the limited amount of bioenergy should be used primarily where the biggest effects on climate protection can be achieved, namely in power and heat generation. Energy losses are incurred in the production of liquid fuels; these reduce both the energy yield and the climate protection effect relative to the amount of biomass used. It is therefore inefficient to use biomass as a liquid fuel for combustion engines. Furthermore, the biggest contribution to climate protection can be achieved by substituting fossil energy carriers that generate high specific CO2 emissions, like coal.
The contribution to climate protection also depends on where the biomass used comes from: the results are often poor in the case of specially grown energy crops, particularly when land is directly or indirectly converted to grow energy crops. The WBGU therefore recommends the preferential use of waste products, which account for about 50% of the sustainable bioenergy potential. Their use for energy generation simultaneously reduces emissions of the methane that would otherwise be generated by decomposition processes.