Keywords: Biofuels, energy, greenhouse gas emission, sustainability.
The use of biofuels, i.e. ethanol and biodiesel, as replacements for gasoline and diesel derived from mineral oil is seen as a measure to decrease the impact of the steadily growing transport sector on the exhaustion of non-renewable mineral oil and on climate change. However, the sustainability of biofuel production is still heavily debated.
Sustainability is a concept with many definitions and many aspects, varying from environmental to socio-economic issues. This paper is focused on calculations of the energy balance and the greenhouse gas balance of biofuel crops, performed with the calculation tool ‘E-CROP’. The authors’ calculations were limited to the crop level and the processing chain; effects of soil organic matter dynamics on greenhouse gas emissions were not included.
Results are shown for several biofuel chains, with variations in the use of co-products and residues. Effects of land use change, land management change and some other sustainability aspects are discussed.
It is concluded that biofuels can make a contribution to energy supply, however the question about sustainability of biofuel crop production remains unanswered. This relates to a large extent to the GHG balances and these can seriously be affected by the effects of land use change and land management change on greenhouse gas emissions, which were not included in the calculations in this paper. These effects may be difficult to quantify; they seem inevitable if biofuel crops are to contribute substantially to energy supply. Other sustainability aspects should also be taken into account, such as biodiversity and nutrient emissions, because there are usually trade-offs between the effects on these other aspects and the desire to produce more biofuel crops.
W J Corré and J G Conijn, Plant Research International, Wageningen University and Research Centre, P.O. Box 16, 6700AA Wageningen, The Netherlands.
27 pages, 3 figures, 8 tables, 25 references