Transforming waste water into renewable energy

As Northumbrian Water’s Wastewater Director, Richard Warneford, leads the company’s treatment works and sludge activities, which have evolved into an industry-leading renewable energy operation

Whenever the term “Power From Poo” is mentioned, it instantly engages whatever audience is being addressed. However, what really draws them in even further is discovering the innovative reality behind the phrase – the way our experts use the sludge left over from our sewage treatment to create green energy.

At Northumbrian Water, we are the only water company to use 100% of its sewage sludge in this way – using a process called Advanced Anaerobic Digestion (AAD) – and our experts are often called upon by other businesses to provide advice and share their experience.

The waste customers flush down the toilet is treated at sites around the North East of England and then we turn it into gas and electricity, which people use to heat their homes and cook their meals.

It’s part of a true circular economy that sees 2,000,000mᵌ of sludge from 3,000,000 customers turned into 10MW of renewable energy.

Our use of AAD has transformed sewage sludge from being a waste product that needed a lot of energy to clean up before it could be returned to the natural environment, into a fuel being used to produce green power.

This is a result, not only of innovative thinking, but of £75 million of investment that helped us to exceed our renewable energy target of 20% two years early, back in 2013. We have also reduced carbon emissions by 30%, towards our 2020 target of 35%.

AAD takes place at two of our sites, at Howdon, North Tyneside, and at Bran Sands, on Teesside. But while the sludge itself does have to be transported to those locations, we have also changed our processes in a way that means it is moved in cake form, rather than as a liquid, reducing transport movements and further cutting our carbon footprint.

Drying out the sludge prior to transport has seen a reduction from 90,000 tankers, containing 2,000,000m ᵌ of liquid, to 10,000 trailers, carrying 320,000mᵌ of cake.

It all sounds pretty impressive, doesn’t it? But we haven’t stopped there.

Having made Power From Poo at Howdon since May 2012, we opened a Biomethane Injection plant there in 2014, to make the process more efficient. This plant is the UK Water Industry’s largest gas-to-grid project and takes the renewable biogas from the AAD process, purifies it to an extremely high quality, and injects it into the public gas distribution network.

At maximum output, 88GWh of renewable energy – enough to supply 7,000 homes – can be passed into the grid annually.

The gas-to-grid plant boosts efficiency in the use of biogas by more than 35%, that’s equal to more than 32GWh per year, compared with the previous process, significantly reducing our reliance on fossil gas and saving 5,902 tonnes of Co2 every year.

Financially, there are also significant savings being made. In total, more than £5m of operational savings are generated each year, contributing to the company’s ability to keep customers’ bills low.

AAD is, however, just one part of our sustainable energy story, and we work with a number if partners to create a really strong energy mix, that also features better known sources, such as wind and, of course, hydro power.

It’s also only one element of our overall innovation strategy that is aimed at keeping at the forefront of the water and wastewater industry, and ensuring we deliver the best services and value for our customers.

We’re even looking at taking Power From Poo another step further, as a result of one of our Innovation Festivals, so keep an eye out for Power From Pooches in the future, as we work with Durham County Council on the potential to add dog waste to the mix.