An accurate evaluation of the sustainability of European oilseed rape for biodiesel production would be a useful resource in discussions of the European Union's bioenergy policies. Your ill-judged pronouncement in an online News report that rapeseed biodiesel fails the sustainability test (Nature http://doi.org/jdn; 2012) risks confusing the facts by quoting questionable figures from a preliminary study (G. Pehnelt and C. Vietze Jena Econ. Res. Pap. 039; 2012).

These figures concern some of the most important parameters used in sustainability calculations. The study considerably underestimated mean annual seed yields of rapeseed used for biodiesel, by using outdated yield values from the entire European Union (around 2.8 tonnes per hectare for 1991–2005), rather than current yields from the principal biodiesel-producing countries such as Germany (3.8 tonnes per hectare for 2005–10; see http://faostat3.fao.org). The input values were also based on energy-intensive production procedures (deodorization, for example) that are only used in processing rapeseed oil for food, and on unrealistic transportation emission values. Incorrect input data can seriously influence the outcome of a sustainability evaluation.

Political decisions need to be based on reasoned and constructive discussion about issues as controversial as renewable biofuels, which in turn must be based on strong, peer-reviewed science.