Greenhouse gas emi
According to Britain's National Non-Food Crops Centre, total net savings from using first-generation biodiesel as a transport fuel range from 25-82% (depending on the feedstock used), compared to diesel derived from crude oil. Nobel Laureate Paul Crutzen however finds that the emissions of Nitrous Oxide due to nitrate fertilisers is seriously underestimated, and tips the balance such that most Biofuels produce more greenhouse gases than the Fossil fuels they replace. Producing lignocellulosic biofuels offers potentially greater greenhouse gas emissions savings than those obtained by first generation biofuels. Lignocellulosic biofuels are predicted by oil industry body CONCAWE to reduce greenhouse gas emissions by around 90% when compared with fossil petroleum, in contrast first generation biofuels were found to offer savings of 20-70%
Some scientists have expressed concerns about land-use change in response to greater demand for crops to use for biofuel and the subsequent carbon emissions. The payback period, that is, the time it will take biofuels to pay back the carbon debt that they acquire due to land-use change, has been estimated to be between 100–1000 years depending on the specific instance and location of land-use change. However, no-till practices combined with cover crop practices can reduce the payback period to 3 years for grassland conversion and 14 years for forest conversion. Biofuels made from waste biomass or from biomass grown on abandoned agricultural lands incur little to no carbon debt.
