An examination of biorefining processes, catalysts and challenges

Biofuels offer the potential to substitute for a large proportion of fossil fuels, however it is considered that the utilisation of lignocellulosic biomass, via second-generation biorefining technologies, will be necessary for this to be achieved economically and sustainably. The lignocellulosic matrix is complex and recalcitrant to conversion but research in biorefining is advancing rapidly and commercial facilities are expected in the near-term. These facilities will either employ hydrolytic mechanisms to break apart the structural polysaccharides of the biomass, or thermochemical procedures to dehydrate and volatilise the feedstock. Catalysts serve vital roles in both approaches: acids and enzymes facilitate the hydrolysis of cellulose; while metal and biological catalysts can alter the volatilisation profiles of biomass or reform the gases that are liberated in the thermochemical process. Each potential biorefining technology currently has its own drawbacks and advantages and it is likely that a range of procedures will be needed in order to fully exploit the values of very diverse ranges of lignocellulosic feedstocks. (C) 2008 Elsevier B.V. All rights reserved.