A Chinese research team has developed a way to convert leather solid waste into fertilizer and other products, solving a problem that has troubled leather companies for years.

Led by Wang Quanjie, a professor of Yantai University, the team can liquify leather waste and turn it into organic fertilizer or construction materials such as adhesives, after researchers remove the heavy metal chromium from the leather sludge.

Wang said that leather waste was rich in protein. In Shandong province, companies have to pay around 1,000 yuan ($150) to dispose of one tonne of waste produced during the leather making process. The new method has just passed review by the Shandong provincial department of science and technology.

China is the world's leading leather producer and consumer. The country produces more than 4.5 billion pairs of leather shoes each year, which generates 1.4 million tonnes of leather solid waste, including 280,000 tonnes containing chromium.

In 2016, China added waste containing chromium to its hazardous waste list, prohibiting it from being disposed through landfill and incineration.