Oil produced from bitumen sands is often referred to as unconventional oil, to separate it from traditional liquid oil. The production process is very energy consuming so that the net energy gain is much smaller compared to traditional oil. Making liquid fuels from oil sands requires much energy and produces 12 percent more greenhouse gases per barrel of final product than production of traditional oil. Therefore oil sands have only recently been considered to be part of the world's oil reserves. Higher oil prices now allow for profitable extraction and processing.