For many years, it was assumed that biodiesel and other biofuels had a net zero carbon footprint, because although burning the fuel does release carbon into the atmosphere, the plant feedstock absorbed carbon as it grew.
However, recently scientists have begun to question the assumption that biodiesel and other biofuels have a net zero carbon footprint. For example, if forestland is cleared in order to plant oilseed crops for biodiesel production, the clearing of the forestland releases enormous amounts of carbon into the air. And if a biofuel is produced in a plant powered by coal, the coal will release a lot of carbon into the atmosphere.
When biodiesel is produced using sustainable, environmentally sound practices, the production and use of the fuel results in less greenhouse gases being released into the atmosphere over the life cycle of the fuel.
In February of 2010, the U.S. EPA released a report analyzing the greenhouse gas impact of biodiesel and ethanol based on the type of feedstock used and the method of producing the fuel. The EPA's Renewable Fuel Standards Program Regulatory Impact Analysis found that on average, corn ethanol produced in a plant powered by natural gas results in a 21% reduction of greenhouse gases compared to gasoline. Soy biodiesel results, on average, in a 57% reduction in greenhouse gases compared to fossil diesel, and biodiesel produced from waste grease results in an 86% reduction.
For more information, see Biofuels and Greenhouse Gas Reductions, and Environmental Life Cycle Analysis of Biodiesel.
