A study by researchers at Massachusetts Institute of Technology (MIT) concludes that the complete carbon footprint of some biofuels is less ‘green’ than conventional fossil fuels.

Airlines, in particular, are increasingly looking to biofuels to provide reductions in carbon emissions and a report out earlier this month by consultants Booz & Company concluded that biofuels are the ‘only credible hope’ to make aviation greener.

But the MIT researchers looked at the entire carbon footprint of 14 fuels – including conventional petroleum-based jet fuel and various ‘drop in’ biofuels produced from different feedstocks – and found that sometimes conventional fossil fuels can be the ‘greener’ choice.

“What we found was that technologies that look very promising could also result in high emissions, if done improperly,” says engineer James Hileman.

Writing in the peer-reviewed journal Environmental Science and Technology, the researchers show that the emissions associated with a particular biofuel depend on the type of land used to grow the feedstock.

The researchers’ calculations indicate that biofuels from palm oil produce 55 times more CO₂ if grown on a plantation in a converted rainforest compared with a previously cleared area. Where land-use change is severe, says Hileman, biofuels can emit ten times more CO₂ than conventional fuel.

Hileman says airlines need to consider carefully how biofuels are produced before moving ahead with large-scale use.

The answer could be two-fold – not only should advanced crops like algae and salicornia, which do not require deforestation of fertile soil to grow, be further investigated, but the byproducts from biofuel production – such as solid biomass – could be used to produce electricity to offset emissions.

For further information:
R. W. Stratton, H. M. Wong, and J. I. Hileman. Quantifying Variability in Life Cycle Greenhouse Gas Inventories of Alternative Middle Distillate Transportation Fuels. Environ. Sci. Technol., 2011, 45 (10), pp 4637–4644

Related stories:
Biofuels are only option to reduce air transport emissions, says study (5-May)
Biofuels could provide 27% of transport fuels by 2050, says IEA (21-Apr)
Biofuel policies are “unethical”, says UK report (13-Apr)
Boeing and EPFL join forces on biomass fuel sustainability standards (25-Mar)