Human waste is certainly plentiful, but clean? In fact, it is -- if used the right way. That's why some British utilities are planning to harness the biomethane gas produced at sewage treatment plants to create residential power for cooking and heating.
"Our customers could be at home frying sausages on gas generated at our sewage treatment works," Mohammed Saddiq, general manager of GENeco, Wessex Water's energy company, told The Independent.
The idea isn't entirely new. For thousands of years, primitive peoples used dried animal manure as fuel – some tribal cultures still do. Utility companies have also used waste product to generate electricity, but only onsite. But this is the first time biomethane will be treated to be suitable for home use. Gas will move straight from sewage plants into the National Grid.
The environmental benefits could be huge, said Dragan Savic, a professor of hydroinformatics at Exeter University. He explained that emissions from the more than 9,000 sewage treatment plants in the United Kingdom are toxic. "Greenhouse-gas emissions reductions could be significant as the methane normally generated at sewage works is 25 times more harmful to the atmosphere than carbon dioxide. By capturing methane and pumping it into the National Grid, water companies could turn from greenhouse-gas emitters into renewable-energy generators."
The British Environment Agency says the UK water industry uses about 8,100 gigawatt hours of energy each year and emits over 4 million tons of greenhouse gases.
Severn Trent and Northumbrian Water are also on board with the plan.
Here's how "poo power" works. The Severn Trent plant treats waste from about 2.5 million people. The resulting sludge is washed, compressed and tested for ignition quality and to ensure it smells like normal methane gas. Then it's pumped into the grid to power its customers' homes.
It may sound "a little unsavory," Simon Farris, Severn Trent's renewable energy development manager, told Bloomberg News. But he stressed that "there's lots and lots of power locked in poo, and when that's processed, it's perfect to generate clean renewable green gas."
There remains one unsavory byproduct, though: Sewage sludge. Severn Trent said in a statement that this matter is fed to "concrete cows" that work like giant cow's stomachs to convert the sludge into gas. So far the utility uses 40 percent of this energy, but plans to use more of it in the future.
In fact, Farris said, energy is Severn Trent's second-highest operating cost, and the use of biomethane has helped it save well over a million dollars a year on gas production.
By Andy Tully of Oilprice.com