Biofuels are promoted to help mitigate global climate change. However, their production can easily lead to significant greenhouse gas emissions resulting from land conversion and other sources. A team of scientists charted greenhouse gas emissions resulting from biofuel production, presenting them as global maps. Dedicated crops grown on grasslands, savannahs and abandoned agricultural lands could provide around 30 exajoules per year (i.e. a third of current global energy consumption for transport) with relatively low CO2 emissions measured over the century as a whole. These findings were published today in Nature Climate Change.
Numerous policymakers and scientists expect biofuels to play an important role in combating climate change. The reason is that the CO2 released when burning biofuel is first absorbed in the production of the crops, resulting in no net emissions from combustion. But there is a down side: biofuel production often requires the use of (new) agricultural land. As a result, large-scale biofuel production can be accompanied by the loss of natural vegetation. “The CO2 stored in the natural vegetation therefore disappears into the atmosphere. What’s more, the vegetation also no longer absorbs CO2”, says principal author Vassilis Daioglou, who is associated with the Netherlands Environmental Assessment Agency (PBL) and Utrecht University. "The disadvantageous aspect must be offset against the advantages of biofuels."
This Nature Climate Change publication is the first study to systematically chart the volume of greenhouse gases released, and present them with respect to the volume of biofuel production. The study was conducted using a global biophysical model, therefore taking account of geographical differences: land Bio-development in Canada’s boreal forest, for example, leads to much higher CO2 emissions than on Argentinian grasslands. But there are also significant differences within a single country.
Potential for biofuel
The maps make it possible to evaluate the long-term impact of biofuel production on different locations. “This also makes it possible to better understand why earlier studies often show a broad range of results – because different assumptions are generally made about the respective specific locations”, adds Detlef van Vuuren, project leader at PBL and professor at Utrecht University. The net effect of the emissions can be compared with that of avoided emissions from fossil fuels. Biofuel could produce around 30 exajoules a year by 2050 without moving into forests, with an emission factor that leads to a halving of fossil fuel emissions. This number would approach 100 exajoules if forest area with low emission factors are included, or if a less strict emission criterion is used. Current energy consumption is around 100 exajoules a year for transport.
Environmental policy will therefore have to ensure that biofuel is only produced at favourable locations. Only under strictly defined conditions can biofuel help us achieve the targets set in the Paris Agreement.