Human waste turned into electricity and fertilizer

In one of our earlier posts we wrote about pee power fuelling up hydrogen cars. Now, scientists from Singapore’s Nanyang Technological University (NTU) have developed a new toilet system that can convert the other, more solid human waste to electricity and fertiliser.

Singapore isn’t rich in natural resources, so the NTU scientists chose to do something with the waste material that was available in abundance. The team from NTU say the poo power toilet they developed ( also known as the No-Mix Vacuum Toilet) reduces the amount of water needed for flushing by up to 90% compared to existing toilet systems in Singapore. The existing conventional water closet is said to use about 4-6 lts of water per flush. If installed in a public restroom flushed 100 times a day, this next generation toilet system will save about 160,000 lts in a year – enough to fill a small pool 10m x 8m x 2m.

The toilet has two chambers which separates the liquid and solid waste. Using vacuum suction technology, such as those used in aircraft lavatories, flushing liquids would now take only 0.2 lts of water whilst flushing solids require just one litre. The No-Mix Vacuum Toilet then diverts the liquid waste into a processing facility where components used for fertilizers; nitrogen, phosphorus and potassium can be recovered. Meanwhile all solid waste is sent to a bioreactor where it will be digested to release biogas which contains methane. Methane is odourless and can be used to replace natural gas used in stoves for cooking or processed to electricity and used to fuel power plants or fuel cells. ‘Grey water’ (used water from the laundry, shower and kitchen sink) can be released back into the drainage system without further need for complex waste water treatment, whilst leftover food wastes can be sent either to the bioreactors or turned into compost and mixed with soil, resulting in a complete recovery of resources.

The No-Mix Vacuum Toilets will be useful for new housing estates, hotels, resorts and especially communities not linked to the main sewage system and so requiring their own sewage facilities. The systyem, that has taken one and a half year to develop, has already received some funding. NTU scientists are now looking to carry out trials by installing the toilet prototypes in two NTU restrooms.



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