Beyond Grain: Feedstock Technologies for the Sustainable Production of Biofuels.

Biofuels represent the only alternative source of liquid transportation fuels compatible with current engine technologies.  Therefore, their use does not require major investments in a new generation of vehicles and in new fuel infrastructure.  Biofuels thus represent a major global opportunity to reduce greenhouse gas emissions, to reduce the dependence on imported oil, and to enhance rural economies.  Biofuels can be produced from lipids and oils derived from oil crops and algae (biodiesel) or from fermentable sugars derived from soluble sugars, starch, or cell wall polysaccharides (ethanol).  A major concern is that biofuels compete directly or indirectly with food production, which results in higher food prices, food shortages, and deforestation of tropical rainforests.  The use of crop residues as a source of cellulosic ethanol is expected to prevent this from becoming a long-term problem, as long as the biomass processing can be made more efficient.  Progress  in both processing technology and plant breeding will be discussed.  Breeding efforts are also underway to address concerns about soil depletion, erosion, and input requirements.  The production of algae has the potential to generate a continuous and ample supply of feedstock for biodiesel, even in production systems that are not suitable for food production.  Despite technological advances and the hype surrounding biofuels, it is important to realize that not all production systems are suitable for feedstock production, and that it may be more economical to import biofuels.  In that case, however, carbon emissions during production and transport should be taken into consideration.  The discussion about biofuels is often plagued by generalizations and oversimplifications, and would benefit from a more rational approach in which technological advances, economic, environmental, agronomic and logistic considerations are used to determine if and how biofuels should be produced.  This applies especially to developing countries with their more limited resources.