KLM Royal Dutch Airlines will buy 2,000 tons of gutter oil from China in mid-July to transform it into aviation fuel later, Xinhuanet reported Tuesday.

Gutter oil, made from leftovers, is often illegally used by some restaurants in China for cooking.

Last November, KLM Royal Dutch Airlines imported 20 tons of gutter oil from Qingdao, a coastal city in China's Shandong province, according to previous reports. The sample was then tested to show whether it could be exploited as jet fuel, said the report.