Most sustainable biofuel crops identified

Palm oil from South-East Asia, sugarcane from Brazil and sweet sorghum from China are currently the most sustainable energy crops. Researchers in the Plant Production Systems Group at Wageningen University in the Netherlands tested 9 energy crops against 9 sustainability criteria. The researchers report these 3 crops make the most efficient use of land, water, nitrogen and pesticides in proportion to the amount of energy they produce. If no forest is cut down to make way for their production, they produce far smaller quantities of greenhouse gases than fossil fuels. The findings have been published in Biomass and Bioenergy.
Major energy crops such as corn in the U.S. and wheat in Europe score much lower on nearly all the sustainability criteria. Sugar beet and oil seed rape (Europe), cassava (Thailand) and soya (Brazil) received an average score.
“We only assessed the production ecology of the crops and not the socio-economic consequences or the impact on biodiversity,” said researcher Sander de Vries.
An advantage of the best crops is that their residues produce enough energy to extract the oil and ethanol. The researchers said to process corn into ethanol, the U.S. currently has to use supplementary fossil fuels since the crop residues are not used to generate energy. They indicated that it is also important that enough crop residues are left behind in the fields to maintain the organic matter level in the soils.
The researchers are now studying a second generation of energy crops, in which the cellulose in the crop residues can be turned into ethanol. This will enable Europe and the U.S. to produce much more energy per hectare with crops such as elephant grass, said De Vries. Until these crops are developed, Devries said the best alternative is to mix energy from certified sustainable sugar cane and oil palms, since these crops produce the most energy per hectare and do the least amount of environmental damage per liter of fuel. 
 Sugarcane has been found to be one of the most sustainable energy crops. Photo courtesy of Wageningen University