Of all the things that people traditionally discard, one that most of us likely think the least about repurposing is human feces and urine. Sure, we recycle our plastic and paper, and compost our fruits and veggies, but ... that stuff? Actually, there are various worldwide projects aimed at using municipal raw sewage for things such as fertilizer or as a power source. While those projects only come into play once the waste has been flushed, however, the UK's Loowatt system gets users involved from the bottom up (sorry), collecting waste directly from the toilet and using it to create biogas and fertilizer.
The Loowatt toilet itself is waterless and chemical-free, and is intended for use at outdoor events, campsites and other remote locations – pretty much the same places that a Porta Potty or outhouse would be used. Feces and urine drop into what is described as an "odorless" sealed cartridge, which incorporates a biodegradable liner. Once or twice a week, that cartridge is removed, and the liner and its contents are dumped into a nearby anaerobic digester.
The digester (which is also part of the system) utilizes microorganisms in an oxygen-free environment, to consume the waste and convert it into methane and carbon dioxide gas. That gas can then be burned for fuel, at which point it reverts back to CO2 and water vapor. Another by-product of the digester is a semi-liquid manure, in which the nutrients have already been homogenized, making them more accessible to plants. This can be separated into liquid plant food, and a more solid manure.
A pilot project is currently operating at a houseboat marina in West London. It consists of five toilets and a small-scale digester, and is apparently working well. "The toilets were successful and we are now in discussions with numerous potential customers," Loowatt's Virginia Gardiner told us. "The digester is producing a steady supply of biogas which we have hooked up for cooking."
The company was recently awarded a US$100,000 Grand Challenges Explorations grant from the The Bill & Melinda Gates Foundation, to develop the technology further. Anyone interested in trying the system out at their location is invited to contact Loowatt.
A similar system is in place at Cambridge, Massachusetts' Park Spark project, in which anaerobically-digested dog feces are used to fuel a gas lamp in an urban dog park.