Sustainable liquid biofuels from biomass: the writing's on the walls

Abstract

Summary: Domination of the global biosphere by human beings is unprecedented in the history of the planet, and our impact is such that substantive changes in ecosystems, and the global environment as a whole, are now becoming apparent. Our activity drives the steady increase in global temperature observed in recent decades. The realization of the adverse effects of greenhouse gas emissions on the environment, together with declining petroleum reserves, has ensured that the quest for sustainable and environmentally benign sources of energy for our industrial economies and consumer societies has become urgent in recent years. Consequently, there is renewed interest in the production and use of fuels from plants. The ‘first‐generation’ biofuels made from starch and sugar appear unsustainable because of the potential stress that their production places on food commodities. Second‐generation biofuels, produced from cheap and abundant plant biomass, are seen as the most attractive solution to this problem, but a number of technical hurdles must be overcome before their potential is realized. This review will focus on the underpinning research necessary to enable the cost‐effective production of liquid fuels from plant biomass, with a particular focus on aspects related to plant cell walls and their bioconversion. Contents Summary 473 I. Historical context 474 II. The case for liquid biofuels in the context of human energy consumption 474 III. Liquid biofuels 474 IV. Converting plant biomass into liquid fuels 475 V. General composition of plant biomass 478 VI. Overcoming the saccharification barrier 482 VII. Tools for cell wall disassembly 483 VIII. Prospects for biofuels 483 References 484