Biofuels
As David Rotman states in his article on biofuels, the conversion of biomass to liquid fuel is energy intensive--just like the conversion of coal or any other solid fuel to liquid fuel ("The Price of Biofuels," January/­February 2008). That implies that the quantity of liquid fuel from biomass and the carbon dioxide released in the production process strongly depend upon the energy source used in the conversion process.

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