Biofuels - Both biodiesel and renewable diesel can be produced from plant or animal oils, fats, and wastes. According to the U. S. Energy Information Administration, the United States uses a combination of oils and fats in biodiesel production: soy oil 65%, corn oil 7.5%, and yellow grease and white grease was less than 8% of production of 8,478 million pounds of feedstock inputs for biodiesel in 2013. According to the latest published life-cycle analysis for various feedstocks and the feedstock mix reported by the Energy Information Administration and the U. S. EPA for 2013, the average GHG reduction for biomass-based diesel exceeds 80%. If biofuels provided a quarter of transport fuel in 2050, it would avoid an estimated 2.1 gigatons of GHG emissions per year. Although biofuels are among the few fuels for medium- and heavy-duty trucking that are considered renewable, there are some issues regarding its status as a sustainable fuel source. The sustainability of biofuels comes into question on several fronts. All BUT ONE is a reason why environmentalists question biofuels as sustainable energy resources.