Sewage heat recovery systems may not sound sexy, but one day they could mean your dirty bathwater helps provide you with more efficient and lower-carbon central heating.
Every day the potential energy contained in vast quantities of warm wastewater disappears down countless drains in the UK and across the world.
But thanks to a pioneering new system, grey water – from baths, showers, washing machines, dishwashers and sinks – can now be exploited to help create a more sustainable future.