The Rationale for Biofuels
As world demand for liquid transportation fuels grows, the surplus production capacity of traditional petroleum reservoirs is approaching a vanishingly small margin, resulting in upward pressure on the global price of petroleum. The utilization of biomass represents one approach, among many that will be required, for meeting future energy needs and reducing greenhouse gas emissions. Although biomass can be utilized in its raw state as an energy source, for example, by co-combustion with fossil fuels for electricity generation, there are compelling reasons to find ways of converting biomass into liquid fuels. Routes for the conversion of biomass to liquid fuels can be classified into two main types: those based on thermochemical processes and those utilizing biological means. Thermochemical processes use heat, sometimes in combination with heterogeneous catalysts, to convert biomass or biorefinery residues, e.g., lignin, to intermediates such as pyrolysis oil and syngas. These intermediates can be used directly as raw fuels, or may be upgraded to produce fuels and chemicals that are interchangeable with existing commodities such as liquid transportation fuels and hydrogen.