Sludge incineration is a sewage sludge treatment process using incineration. It generates thermal energy from sewage sludge produced in sewage treatment plants. The process is in operation in Germany where Klärschlammverbrennung GmbH in Hamburg incinerates 1.3m tonnes of sludge annually. The process has also been trialed in China, where it has been qualified as an environmental investment project. However the energy balance of the process is not high, as sludge needs drying before incinerating.