A prison in Malawi realised it was flushing valuable fuel down the drains – now it is using the power of poo to fuel its busy kitchens, aiding both inmates and forests. //

The prison was installed with a biogas digester, a system that converts organic matter – including human waste – into energy. Made from plastic sheets, the system has an inlet that feeds the poop and other waste into a digester, where they are submerged in water. The water creates an anaerobic environment that allows bacteria to break down the biomass into methane, which is pushed through a piping system to the gas stoves in the prison's kitchen. //

The prison's officials say that since the installation of the biogas digester the reformatory has cut its firewood consumption by around half, from 60 cubic metres a month to around 29 cubic metres. The digester has also helped to reduce the electricity bills at the prison, saving an average of MWK 310,400 (£290/$400) each month on firewood and electricity.