Biofuels

Abstract

Increasing pressure to move towards energy sustainability and reduce society's dependence on fossil fuels has led to much research and development in the area of biofuels. First-generation biofuel production (e.g., ethanol from corn) is a mature technology, but competition with food crops raises questions about sustainability. Second-generation biofuels are produced from waste biomass and thus are perceived as more viable, but technology is not ready for large-scale implementation particularly due to the hydrolysis challenge. The third generation of biofuels captures sunlight directly as fuels or fuel precursors via photosynthesis. Prokaryotic organisms play a crucial role in the majority of the processes involved in biofuel production. Pure culture bioproduction includes ethanol from Zymomonas mobilis, modified Escherichia coli, and Clostridia. However, pure cultures are only efficient at the conversion of sugary biomass, not lignocellulosic biomass. They have thus limited applicability towards second-generation biofuel production. Pure culture prokaryotic biodiesel production is also being investigated (mostly using cyanobacteria). However, similarly to eukaryotic biodiesel production, energy efficiencies are still poor. Mixed culture production is thus far the most successful process at converting complex waste biomass to usable fuels, mainly methane through anaerobic digestion, which is perceived by many as the biofuel technology with highest potential.