Recycling waste took on a very new meaning for 200 households in one Oxfordshire town recently, when they became the first in the UK to receive a supply of renewable gas for cooking and heating made from their own sewage. If all goes according to plan, this £2.5 million project – along with a number of others currently being planned and developed elsewhere – should be just the beginning of moves designed to pave the way for decarbonising gas supplies across the country.
A New Twist on Biogas
There’s nothing new about making biogas from sewage; it’s something that wastewater treatment plants around the UK – and, indeed, the world – have been doing for decades. Purpose-built vessels are used to house the bacteria required to break down the sewage in a sort of airless composting process known as anaerobic digestion, which produces a methane-rich mix of gases which then drive generators to provide some of the plant’s power. This kind of biogas is far from pure, however, containing a number of rather smelly and often corrosive components such as sulphur along with the methane, which make it unsuitable for domestic use.
The key to making the project work lay in successfully adapting the sewage gas for use in household kitchens and boilers – turning ‘dirty’ biogas into ‘clean’ biomethane – and that required an additional treatment plant to be installed at the Didcot sewage treatment works. Now, after the solid ‘sludge’ has been separated from the wastewater arriving at the plant, and then been treated in a conventional digester, the impurities are scrubbed from the gas produced allowing it to be fed straight into the existing gas grid for delivery and use.
Keeping it Local
The idea of ‘energy miles’, like food miles, is something which has become increasingly well used and widely understood over recent years and if there was ever an example of keeping energy production local, it has to be this project. From flushing the toilet, to receiving the gas back for use involves a round trip of just a few miles, and a wait of about three weeks.
As John Morea, CEO of Scotia Gas Networks explained at the launch barbeque – which featured food cooked on biomethane gas, naturally – quite literally providing households with their “own” gas rather than importing it from Russia or the North Sea has to be recycling at its best.
Looking to the Future
All three of the project partners – Thames Water, British Gas and Scotia Gas – clearly see massive potential for the use of biomethane, particularly when it comes to meeting UK and European targets for renewable energy. Although the idea may have led to some raised eyebrows at first – and possibly some wrinkled noses too – there is a lot in its favour and this kind of clean biogas is undoubtedly a sustainable form of energy!
It is still early days for the Didcot project, of course, but it has already been described as “historic,” a “milestone” and “the next logical step.” If it continues to prove so successful and well thought of, then in the long run, there seems to be no reason why initiatives like this shouldn’t ultimately become established across the length and breadth of Britain.
After all, every sewage treatment works in the country is a potential source of renewable gas, just waiting to be used – and when that happens, being part of an energy saving community will suddenly mean something altogether different for everyone!