Biodiesel refers to a non-petroleum-based diesel fuel consisting of short chain alkyl (methyl or ethyl) esters, typically made by transesterification of vegetable oils or animal fats, which can be used (alone, or blended with conventional petrodiesel) in unmodified diesel-engine vehicles.
Biodiesel is distinguished from the straight vegetable oil (SVO) (aka "waste vegetable oil", "WVO", "unwashed biodiesel", "pure plant oil", "PPO") used (alone, or blended) as fuels in some converted diesel vehicles. "Biodiesel" is standardized as methyl ester and other non-diesel fuels of biological origin are not included.
Ethyl Stearate is an Ethyl Ester produced from Soybean or Canola oil and Ethanol. Biodiesel is biodegradable and non-toxic, and typically produces about 60% less net-lifecycle carbon dioxide emissions, as it is itself produced from atmospheric carbon dioxide via photosynthesis in plants. Its emissions of smog forming hydrocarbon are 67% less, although the Nitrogen Oxide emissions are about 10% greater than those from petroleum-based diesel. Net-lifetime carbon dioxide emissions can actually differ widely between fuels depending upon production methods of the source vegetable oils and processing methods employed in their creation. It is therefore debatable as to the extent that biodiesel reduces total carbon dioxide emissions currently contributing to anthropogenic global warming compared to those from petroleum-based diesel.