Here's a paper on the subject, concluding that the land use changes from converting forest to biofuel production actually results in more co2 emission than generating the energy from fossil fuels (https://science.sciencemag.org/content/319/5867/1235): "Our results demonstrate that the net effect of biofuel production via clearing of carbon-rich habitats is to increase CO2 emissions for decades or centuries relative to the emissions caused by fossil fuel use. Conversely, biofuels from perennials grown on degraded cropland and from waste biomass would minimize habitat destruction, competition with food production, and carbon debts, all of which are associated with direct and indirect land clearing for biofuel production."

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