Biofuels are a type of renewable energy derived from biological carbon fixation. They include fuels produced from biomass conversion as well as solid biomass, liquid fuels, and biogases. Factors such as rising oil prices, energy security concerns, and reducing greenhouse gas emissions are driving increased attention to biofuels. Biomass can be used to produce transportation fuels like ethanol and biodiesel, as well as thermal energy. Advanced biofuel production may utilize biorefineries that integrate processes to produce multiple fuels and chemicals from biomass, analogous to petroleum refineries. Environmental impacts of biofuel production include both benefits like carbon neutrality and waste reduction, and concerns over air and soil pollution.