The Past, Present, and Future of Biofuels – Biobutanol as Promising Alternative

Abstract

While the worldwide energy consumption is projected to grow by 57 % until 2030 (U. S. Energy Information Administration [EIA], 2007) fossil sources are limited and it is questionable how long they will last. Meanwhile, even unconventional sources such as tar sands and oil shales become economically producible since crude oil prices have reached sustained highs and even surpassed a historic mark of US$ 145 per barrel in June 2008 (EIA, 2011). Besides concerns about avaibility and prices of fossil fuels as well as the quest for energy independence, there is also an intense discussion about environmental impacts. Burning of fossil fuels leads to a massive increase of the greenhouse gas CO2 in the atmosphere and is thus contributing to global warming (Intergovernmental Panel on Climate Change [IPCC], 2007). This could be counterbalanced by using alternative energy sources. Biofuels are the most promising alternative energy for the transportation sector, which is most rapidly growing (an annual average of 3 % is projected until 2030, especially due to increasing mobility in China and India) and accounts for over 20 % of the worldwide primary energy (EIA, 2010). Biofuels can either be produced microbially or chemically from renewable biomass and are therefore CO2 neutral. However, only few compounds such as alcohols (ethanol, butanol), alkyl esters of fatty acids (biodiesel), and alkanes (renewable diesel) have the required properties. Today, only bioethanol, biodiesel, and renewable diesel are produced at industrial scale, but several second generation technologies are on path to commercialization. Especially biobutanol fermentation seems to be a promising alternative.