Biodiesel defined ...
... "What is biodiesel? Biodiesel is a cleaner-burning diesel replacement fuel made from vegetable oil. Using biodiesel in a conventional diesel engine substantially 
reduces emissions of unburned hydrocarbons, carbon monoxide, sulfates and particulate matter. Biodiesel is also much less toxic to the environment than petroleum-based diesel and biodegrades much faster. " ...
Biodiesel Definition: Via Wasington State Department of Ecology: Biodiesel in underground storage tanks (PDF) ...