At an upmarket restaurant in the hotpot-loving Chinese city of Chengdu, diners plunge sliced meat and vegetables into cauldrons of spicy, oily broth, largely unaware that their leftovers are set to take on a second life as jet fuel. With around 150,000 tonnes of used hotpot oil thrown out by restaurants in the city each year, local business Sichuan Jinshang Environmental Protection has found a niche in processing the greasy waste and exporting it to be turned into aviation fuel.
The biofuel is produced using hydro-processing of fatty acids (HEFA), which turns waste vegetable and animal fats into aviation fuel, or sustainable aviation fuel or SAF, the industry’s term for a non-fossil alternative. It can be made from recycled cooking oil, wood waste, palm oil, and other plant sources such as algae. SAF offers the potential to lower airliner emissions, but it is still more expensive than traditional petroleum-based jet fuel.
It is also less pure, and some experts believe it may contain carcinogenic chemicals such as acrylamide, formed when starchy foods are cooked at high temperatures. For these reasons, airlines have been cautious about using SAF in commercial flights, and most have opted to mix it with conventional jet fuel.
But SAF is becoming increasingly popular with airlines as regulators and consumer pressure mount to cut carbon dioxide emissions from air travel. The International Civil Aviation Organization recently set a target for international airlines to slash their carbon footprints to nearly zero by 2050.
Aircraft manufacturer Boeing is working with the state-owned Commercial Aircraft Corp of China to build a facility in the eastern city of Hangzhou that will turn 1.8 billion liters of gutter oil a year into aviation fuel. The company says it could help cut the average plane’s carbon emissions by almost 40% if China’s airlines switched to its biofuel blend by 2030.
Boeing and COMAC plan to fly a Boeing 737 on a 50/50 blend of SAF and conventional fuel in Shanghai this month, a milestone showing the fuel’s viability for commercial flights. The companies expect to begin all commercial flights using biofuel in 2020.
But China’s appetite for spicy hotpot and other fried delicacies means that its surplus of cooking oil will soon outstrip the demand for SAF. Jinshang aims to double its production capacity this year by building new facilities and collecting more oil from provinces beyond the Sichuan region. It is planning to build its refineries to produce the biofuel itself. Those efforts could eventually be enough to meet about 4% of global demand for sustainable jet fuel by 2030.