Biodiesel Blend (B20)
Diesel mixed with fuel made from vegetable oils or fats. The number is the percentage of biodiesel, so B20 is 20 percent biodiesel and 80 percent petroleum diesel.
Biodiesel blends into ordinary diesel and runs in ordinary diesel engines, which is what makes it attractive: no new vehicles and no new infrastructure. B20 is the common fleet blend.
Two operational points matter more than the emissions case. Engine manufacturers state which blends they approve, and exceeding that can affect warranty, so the specification and the fuel contract need to agree. And biodiesel has cold-weather handling characteristics that differ from petroleum diesel, which is a real consideration for a northern fleet running plows in winter.