Environmental Impact
Most studies have found that producing biofuels usually yields reductions in greenhouse gas emissions provided the most efficient systems are used and carbon dioxide emissions from changes in land-use are excluded.
However, changes in land use can have dramatic effects on greenhouse gas emissions. When forests are converted to farmland to produce feedstocks, or to produce crops that have been displaced by feedstock production, carbon stored in the soil is released into the atmosphere. The effects can be so great that they negate the benefits of biofuels. Repaying this ‘carbon debt’ could take decades or even hundreds of years. In some cases, it would be more cost-effective to strive for greater fuel efficiency and carbon sequestration through reforestation and forest conservation.