Renewable Gas from Wastewater Treatment Plant Fueling UK Homes

Extracting energy from “processed poo” to help power homes in the Birmingham area is what Severn Trent Plc, Britain’s second-largest publicly traded water company, is now doing to generate a cost-saving renewable gas.

The utility’s clients near the Minworth treatment plant are able to cook with “green gas” produced from their own sewage after Severn Trent started injecting the bio-methane into the gas grid last week. The gas becomes as clean, “exactly the same,” after treatment as normal gas. This is the first time in the U.K. a water company has delivered bio-methane to the grid. Companies previously used it only on-site.

“Local domestic customers will be able to tap into the energy contained within the biogas and bio-methane as it’s injected into the grid,” Simon Farris, Severn Trent’s renewable energy development manager, said Sept. 30 by phone.

The 8.4 million-pound ($13.6 million) facility treats sewage from about 2.5 million people. This produces a sludge that’s fed into systems that break it down into gas then washed, compressed and tested for quality and odor to ensure it smells like normal gas. After that it’s injected into the gas supply network to power local homes.

“Although it’s a little unsavory, there’s lots and lots of power locked in poo, and when that’s processed it’s perfect to generate clean renewable green gas,” Farris said in a statement.

‘Concrete Cows’

As part of the wastewater-treatment process, sewage sludge is produced. This is fed to 16 anaerobic digesters at Minworth, or “concrete cows which work like giant cow’s stomachs to digest the waste material to produce energy in the form of gas,” Severn Trent said. “Currently, we use 40 percent of this energy to make electricity but more can be done.”

Under pressure from the U.K. water regulator Ofwat to keep customer bills low, Severn Trent turned to “poo power” as part of a series of measures to boost efficiencies and reduce expenses. As energy is its second-highest operating cost, Farris said, this enables the company to save as much as 1.7 million pounds a year on its gas bill.

Ofwat published draft prices earlier this year that water and sewage-treatment companies, including Severn Trent and United Utilities Group Plc, can charge customers for the five-year period starting 2015. The proposals may see average bills drop about 5 percent even after deducting inflation. Ofwat’s expected to make a final decision on prices in December.

Severn Trent submitted a business plan to Ofwat that proposed limiting household bills to 2020 to an equivalent of 1.2 percent below inflation a year, with a price freeze in 2015 and below-inflation rises the remaining four years.

Food Scraps

It’s not just human waste the utility is eyeing to help deliver price cuts. It’s also turning to food scraps. The company in June said it’s building a 13 million-pound facility in central England that will turn food waste into energy and it plans similar plants across the Severn Trent region.

Whether Severn Trent decides to roll out similar plants at other treatment plants depends on the result of a government consultation on subsidies, Farris said. The Department of Energy and Climate Change is currently reviewing how much it pays organizations that feed bio-methane into the grid. A date hasn’t been set for a decision.

Without the subsidy, the technology isn’t yet economically viable, Farris said. “It needs to have an incentive at this stage. The hope is that over time the costs of this will come down as the technology becomes more established.”

Severn Trent isn’t the only water utility experimenting with poop. Thames Water Utilities Ltd. in 2010 started a 250 million-pound program to turn sludge to power across a number of sewage-treatment works. And Wessex Water Services Ltd. has produced biogas it used to power a Volkswagen Beetle car.

Copyright 2014 Bloomberg.

Lead image: Wastewater Treatment Plant via Shutterstock

See our story: Advanced Anaerobic Digestion: More Gas from Sewage Sludge

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