Limits to biofuels

Abstract

Summary. -Biofuel production is dependent upon agriculture and forestry systems, and the expectations of future biofuel potential are high. A study of the global food production and biofuel production from edible crops implies that biofuel produced from edible parts of crops lead to a global deficit of food. This is rather well known, which is why there is a strong urge to develop biofuel systems that make use of residues or products from forest to eliminate competition with food production. However, biofuel from agro-residues still depend upon the crop production system, and there are many parameters to deal with in order to investigate the sustainability of biofuel production. There is a theoretical limit to how much biofuel can be achieved globally from agro-residues and this amounts to approximately one third of todays' use of fossil fuels in the transport sector. In reality this theoretical potential may be eliminated by the energy use in the biomass-conversion technologies and production systems, depending on what type of assessment method is used. By surveying existing studies on biofuel conversion the theoretical limit of biofuels from 2010 years' agricultural production was found to be either non-existent due to energy consumption in the conversion process, or up to 2-6000 TWh (biogas from residues and waste and ethanol from woody biomass) in the more optimistic cases.

An Overview of Promising Alternative Fuels for Road, Rail, Air, and Inland Waterway Transport in Germany

“…As noted earlier, the palm oil-based biodiesel share of total biodiesel is about 23%. The potential of first-generation, conventional biomass-based fuels' potential to satisfy transport sector energy demand is low [51,52]. Furthermore, their sustainability and macroeconomic benefit due to conflicts regarding land use for growing food, as discussed above, is questionable [51].…”

“…The potential of first-generation, conventional biomass-based fuels' potential to satisfy transport sector energy demand is low [51,52]. Furthermore, their sustainability and macroeconomic benefit due to conflicts regarding land use for growing food, as discussed above, is questionable [51]. Assuming that conventional biofuels will drop to 0% after 2030 and advanced biofuels such as biogas methane will replace them, the calculated biomass potentials shares on total transport sector energy demand will be reduced to 0.6-5.5% (18-158 PJ) and a maximum of 22.1% (638 PJ).…”

“…This share is increasable by importing biomass from other countries. In terms of biofuel imports, the current literature reveals uncertainty and concerns regarding large quantities of sustainablyproduced sources [51,53,54]. With respect to land use efficiency, biofuels are, with a difference by a factor of up to 1000, significantly lower than e-fuels [53].…”