There absolutely is evidence that biofuel production adversely affects the environment. For example, Brazil is losing vast amounts of rainforest that is clearcut and burned to plant biofuel crops [2]. It has also been shown that, in the third world, biofuel combustion for heating, cooking, etc., results in 17% of the carbon dioxide and 50% of the carbon monoxide emissions that fossil fuel use does [1]:
The emissions of CO from biofuel use in the developing world, 156 Tg, are about 50% of the estimated global CO emissions from fossil fuel use and industry. The emission of 0.9 Pg C (as CO2) from burning of biofuels and field residues together is small, but nonnegligible when compared with the emissions of CO2 from fossil fuel use and industry, 5.3 Pg C. [1]
In the US, corn and switchgrass biofuel production by fermentation to ethanol increases carbon emissions significantly:
By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. [3]
References:
- http://www.agu.org/pubs/crossref/2003/2002GB001952.shtml
- http://www.reuters.com/article/2007/04/18/environment-biofuels-forests-dc-idUSL1755907420070418
- Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change. T Searchinger, et al. Science 29 February 2008: 319 (5867), 1238-1240.[DOI:10.1126/science.1151861]