It makes up roughly 80 percent of biodiesels in the European Union, but rapeseed oil may not qualify as environmentally sustainable under European law.

Research by economists Gernot Pehnelt and Christoph Vietze of GlobEcon, a German-based reseach institute, argues that the European Commission's calculations of the sustainability of rapeseed oil biodiesels are incorrect. Using the same data quoted by the Commission, the economists struggle mimic the same findings, and question whether the emissions savings from using rapeseed oil as a biodiesel are being overstated.

The 2009 Renewable Energy Directive (RED), issued by the European Commission, states that biodiesels used within the EU for transport have to generate at least 35 percent less greenhouse gas emissions than equivalent fossil fuels. After 2017, biodiesels must provide a saving of at least 50 percent over fossil fuels. Those figures include the entire production life of the fuel -- so everything involved in cultivating, growing, harvesting and consuming the rapeseed oil is taken into account.


In the latest study, however, Pehnelt and Vietze find it difficult to tally the Commission's findings with publicly available research. The RED states that across the whole production chain rapeseed oil biodiesel gives a typical saving of 45 percent, or a lower default value of 38 percent when taken in isolation from transport and other factors.

Yet the best savings figure that the study can find is only 29.7 percent -- not only lower than either of the figures the Commission use, but also below the legal requirement for a biodiesel in the EU. This was despite Pehnelt and Vietze calculating greenhouse gas emissions from rapeseed biodiesel across a large range of situations -- including taking into account soil quality, fertilisers, the fuel used by farming equipment, and whether carbon capture technology was used to offset other emissions.

The authors write: "We are not able to reproduce the greenhouse gas emissions saving values published in the annex of RED.

Therefore, the emissions saving values of rapeseed biodiesel stated by the EU are more than questionable." This is particularly pertinent as 80 percent of biofuels produced within the European Union are currently derived from rapeseed oil.

Growing crops for use as fuel has begun attracting more controversy of late as global food prices spike -- just last week the UN called on the US to abandon its targets for turning corn crops into biofuels.