An innovative solution to reduce the environmental impact of managing sewage sludge by turning it into a source of hydrogen and low-carbon products is one of the winners of a £40 million competition from Ofwat, the water regulator.
The Sewage Sludge Gasification project is a novel approach to sludge management that has today been awarded £2.3 million by Ofwat’s Innovation Fund. The project is one of 17 solutions awarded a share of £40 million in the water regulator’s latest innovation competition – the Water Breakthrough Challenge 4. Each solution is committed to fostering innovative approaches to water and waste management.
Sludge is a bi-product of treating sewage – a treated combination of solid matter and dead bacteria left over from the treatment process. The treated sludge is pathogen-free, rich in phosphorus and nitrogen, and has, for many years, been used in agriculture to enrich soil and improve its moisture retention.
Across the UK and Europe, there is a growing realisation that sludge also poses environmental challenges, since it may also contain microplastics, metals and PFAS (indestructible chemical compounds, also known as “forever chemicals”) which may enter the soil and eventually waterways. Innovative alternatives to managing sludge are needed.
Led by Yorkshire Water, the Sewage Sludge Gasification project seeks to alleviate significant challenges for the UK water industry and offer an alternative to recycling sludge to land.
The Advanced Thermal Conversion gasification process will convert treated sewage sludge into usable products such as biochar, vitrified ash ‘stones’ and a hydrogen-rich synthesis gas (syngas). By operating at a high temperature, the process aims to destroy other contaminants such as forever chemicals including PFAS and microplastics.
The project will demonstrate the circular economy in action by testing the biochar to treat wastewater and also as an additive in brick manufacturing. The carbon-rich biochar, which resembles small pieces of charcoal, could also be used as a soil improver to increase water and nutrient retention, and as it doesn’t readily decompose, it’s also a vehicle for sequestering carbon in soil – though it must be properly managed to ensure soil pH levels are not negatively impacted.
The vitrified ash ‘stones’ could be used as aggregate in the construction industry to reduce the embodied carbon footprint of concrete. Syngas is a blend of hydrogen, carbon monoxide, carbon dioxide and methane, and has the potential to be used to produce green electricity, along with other high-value products.
The Water Breakthrough Challenge is part of a series of competitions from Ofwat, run by Challenge Works with Arup and Isle Utilities, designed to drive innovation and collaboration in the sector to benefit individuals, society and the environment
Yorkshire Water suggests that by using a power optimised plant configuration the gasification process could take the 160,000 dry tons of sludge it produces each year and generate around 50Mwe of power – enough that the gasification process would be energy self-sufficient.
On a national level, the UK produces around 1.2 million dry tons of sludge per year and this is increasing. The gasification process could potentially covert this sludge sustainable products, remove all sludge to land and generate 375 MW of renewable energy for use by the wider industry.
Other winners include £1.8 million to investigate how to remove and destroy PFAS, £6.2 million to prove the concept of sewage sludge pyrolysis, £1.9 million to recover heat from sewers and use it as an energy source, and £700,000 to stimulate the market for biochar.
Dr Danielle Hankin, Innovation Programme Manager, Yorkshire Water, said: “Converting treated sewage sludge into gas, biochar and ash ‘stones’ opens up new, more sustainable uses for this waste product. We’re proud to be pre-empting changes in legislation and consumer attitudes, by delivering a groundbreaking technology that benefits customers, the environment and future-proofs the water industry.
“Once proven, the gasification process will produce sustainable wastewater treatment media and construction material, generate green electricity, and could create high-value products such as biomethanol aviation fuel or hydrogen. Our work represents a pivotal step in driving the UK towards a greener, more resource-efficient future.”
Helen Campbell, Senior Director, Ofwat said: “What we do with treated sludge is not the most glamorous of subjects but cannot be ignored. The current approach of spreading treated sludge to land has environmental consequences, which could include microplastics and forever chemicals – both of which may enter the water system and affect water quality. This is not a problem unique to the UK – alternative solutions are needed around the world. The Innovation Fund has awarded funding to four projects today that will help accelerate innovative solutions to the problem and provide wider environmental benefits in the process.”
The Water Breakthrough Challenge is part of a series of competitions from Ofwat, run by Challenge Works with Arup and Isle Utilities, designed to drive innovation and collaboration in the sector to benefit individuals, society and the environment.
It supports initiatives that help to tackle the biggest challenges facing the water sector, such as achieving net zero, protecting natural ecosystems and reducing leakage, as well as delivering value to society.
Beyond sludge-focused solutions, the competition also acknowledged projects looking to better monitor leaks via self-driving robots in pipes and technology to non-invasively repair underground pipes.
