Biodiesel is a fuel manufactured from vegetable oils and fats, through a process called transesterification. It is also referred to as FAME (Fatty Acid Methyl Ester). The most common basis is rape seed or sunflower, which can be blended with conventional diesel, but given that the energy efficiency well-to-wheel is low, and, also produces more NOx emissions with the present vehicle fleet. However, CO2 emissions decrease by about 60% compared with regular diesel, although there is limited potential for production of large quantities. Note: Volvo's products are today compatible with biodiesel when blended into diesel.