Some Japanese researchers have come up with a way to cleanly burn fuels such as lignite, which produce a lot of pollution due to their high water and sulphur content. Researchers at the Japan Chemical Innovation Institute and the National Institute of Materials and Chemical Research near Tokyo say a commercial version of their fuel combuster could render expensive scrubbing filters on power stations unnecessary. The starting point was water in a "supercritical" state, at which it resembles both a liquid and a gas (this happens at temperatures above 374C). This was combined in a pressure chamber with some alkalis and an oxidiser and brown coal was added. After burning, the residue of brown coal was ammonia instead of the polluting nitrous oxide ( New Scientist , Vol 164, No 2208).