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Keywords:

  • lignocellulose;
  • biomass, biofuels;
  • biorefineries, economics;
  • pyrolysis, gasification;
  • hydrolysis;
  • sugar;
  • fermentation

Abstract

Governments across the world are stimulating the valorization of local biomass to secure the energy supply, reduce the emissions of fossil CO2 and support the rural economy. A first generation of fuels and chemicals is being produced from high-value sugars and oils. Meanwhile, a second generation, based on cheaper and more abundant lignocellulosic feedstock, is being developed. This review addresses the variety of chemistries and technologies that are being explored to valorize lignocellulosic biomass. It shows the need to ‘deoxygenate’ the biomass and reviews the main chemical routes for it, i.e.

a) the pyrolysis to char, bio-crude or gas;

b) the gasification to syngas and its subsequent conversion, e.g. to alkanes or methanol;

c) the hydrolysis to sugar and their subsequent upgrading to oxygenated intermediates via chemical or fermentation routes.

The economics of biomass conversion also needs to be considered: the current production cost of biofuels are typically $60–120/barrel of oil equivalent. Influential factors include the cost of the biomass at the plant gate, the conversion efficiency, the scale of the process and the value of the product (e.g. fuel, electricity or chemicals). © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd