Making Biofuels Competitive: The Limitations of Biology for Fuel Production

Our main energy consumption is based on the use of non-sustainable sources (fossil fuels). The use of biological entities utilizing renewable (biomass) is one way to provide energy rich compounds and molecules for fuels, with emphasis on liquid fuels. Their utilization could substitute for a part of our present use of fossil fuels with the added attractiveness that they have the potential to be sustainable. Bio based fuels have been classified as first, second and third generation fuels. First generation biofuels are already produced on a large scale, mainly bioethanol and biodiesel. The present manufacture of both compounds is regulation driven and subsidized. Second generation biofuels are based on cellulose or waste and are still mainly in research and development phases. The first large scale facilities were launched in 2014. Pretreatment of the lignocellulose and the complexity of waste as a substrate are the economic impediment for these raw materials. Third generation biofuels are higher alcohols (butanol), hydrogen, other drop in fuels (hydrocarbons, isoprenoids) and the use of algae with CO 2 as carbon and light as energy source. The compounds produced by algae that are of interest as biofuels are fatty acids for biodiesel production or ethanol. Except for bioethanol produced in Brazil, which is based on sugar cane as substrate, and during periods of positive economics, these processes do not allow free competition with non-sustainable energy sources. It is important to have a holistic view at the whole life cycle of the processes in order to develop a competitive alternative fuel. The benchmark is economic competiveness compared with conventional fuels. There are many intrinsic limitations for implementation of economical biofuel production one of which is thermodynamics. However, with these intrinsic limitations continued research should be able to give novel and creative solutions to solve the problem of economical competitiveness. The evaluation of the thermodynamical feasibility of the possible pathways is a first requirement. Novel pathways of cellular energetics, related to what is thermodynamically possible need to be developed. The recent decrease in price for fossil fuels, the development of novel sources (i.e. shale gas) has had a very negative effect on the progress in the biofuels manufacture and marketing. Recent standards for volumes to be reached in the coming years are decreasing both in Europe and in the USA.