Biodiesel is a substitute diesel fuel made from biomass, which means that it is inherently renewable and, in itself, it contributes nothingĀ  to carbon-dioxide loading of the atmosphere. Biodiesel commonly uses soybean or canola oil as its base, but animal fat or recycled cooking oil can also be used. The commercial product is a blend of 20% biodiesel and 80% petroleum diesel fuel, hence the name B20.