The Complex Issue Of Biofuels And Co2 Emissions

With and agreement in place to produce 10% of transport fuel from biofuels by 2020 in Europe and the UK it is important to consider the impact this is going to have in the overall strategy of reducing CO2 emissions. Biofuels have been constantly criticised for the fuel/food competition for land that results in their growth. However the disadvantages of biofuels do not stop there. The loss of food crops for biofuels often means that these food crops have to sourced from elsewhere. The CO2 emissions caused by this transference of food crop agriculture has to be taken into consideration when considering the CO2 emissions for biofuel. This is often termed the indirect CO2 emissions. For example soybeans grown in America and rapeseed in Europe for biodiesel or sugar beet for bioethanol have large indirect CO2 emissions as the feedstock crops they replace are still required to feed livestock and so must be grown elsewhere. Conversely in South America and SE Asia where sugar cane and palm oil are grown the indirect CO2 emissions may be small as they have not displaced food crops but the direct CO2 emissions are greater as rainforest is often destroyed to make way for their cultivation.

Biodiesel from algae may be considered a way of producing biofuels with a carbon footprint less than that of conventional fuels but even here the answer depends on how the algae is grown. If it is grown in open ponds the energy required is less and therefore the CO2 emissions less than conventional diesel. However in open ponds the water required for their growth is subject to evaporation and therefore they can be fairly water intensive. Furthermore they have lower yields than other forms of algae production. High yields can be produced by cultivating algae in closed air lift bioreactors made of transparent tubes but here the amount of energy required to move the algae around to give it enough sunlight makes its carbon footprint considerably greater than that of conventional fossil fuels.

As usual when looking at the issues around climate change and CO2 emission targets the picture is not clear. Looking at the immediate swap of biofuels for fossil fuels would appear to suggest a reduction in CO2 emissions but this is never the whole picture. Biofuels will impact land use, energy input and water; all of which need to be taken into consideration when when building policies around alternatives to fossil fuels.