Biodiesel is a cleaner burning diesel replacement fuel made from natural, renewable sources such as new and used vegetable oils and animal fats. Biodiesel operates in compression-ignition engines. Pure biodiesel (B100) is considered an alternative fuel under the Energy Policy Act of 1992. B100 is generally not suitable for use in low temperature conditions. Transportation and storage of B100 requires special management. Lower-level biodiesel blends are not considered alternative fuels, but covered fleets can earn EPA credits in blends of 20% or higher.