Grease, fat and other waste from London households and businesses are building up like mini-mountains, or so called 'fatbergs', in the UK capital's 19th century sewers.
The waste is not just clogging up the underground system, but also costing the company that runs it more than a million dollars a month.
Now there are plans to try to stop part of the problem before it begins, by installing drain storage, and turning the accumulated fats into renewable fuel for new power stations.
Al Jazeera's Emma Hayward reports from London.
Source: Al Jazeera