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Perfecting ‘poo power’ to generate green electricity at peak times

Friday 12th November 2021 13:41

A-gravity-belt-thickener-in-the-gbt-building-monitoring-thickness-of-sludge-on-the-belt

A technician checks the thickness of sewage sludge - which can be used to generate green electricity

Scientists from Thames Water, in partnership with the University of Surrey, have perfected the art of transforming sewage into green electricity at peak times as part of efforts to mitigate the effects of climate change and meet the UK’s net-zero target.   

It is hoped the new science will be adopted industry-wide, contributing to the decarbonisation of the national grid by 2035. Thames Water aims to reach net-zero emissions by 2030 – 20 years before the UK government’s own target – and be carbon negative by 2040. 

Britain uses the most power between 4pm and 7pm, when many families are at home using energy-hungry appliances like ovens, dishwashers and kettles. At this time of day, especially during autumn and winter, electricity prices rocket in line with the increased demand.  

Thames Water worked with sustainability experts at the University of Surrey on a four-year project to boost the production of biogas from sewage, which can then be used to generate enough green electricity to power its sewage treatment sites during this peak period. 

Not having to import green power at this time of day means there’s more for everyone else. It also means Thames Water’s own energy bills are reduced. 

The research was successfully trialled at Thames Water’s Beddington sewage works in Croydon and is now standard practice at the site.  

If rolled out industry-wide, it will help make the UK’s electricity supply cleaner, greener, and more resilient at peak times when customers need it most. It also makes the water industry more resilient to energy price rises. 

Mauro Lafratta, of Thames Water’s energy performance and change team, who led the project while an engineering student, said: “We get all our electricity from renewable sources, but wind and solar can’t always guarantee to produce enough to meet everyone’s demand, especially at peak times.   

“Our research proved we can produce more biogas in peak periods to generate electricity when the grid’s prices and carbon emissions peak. This solution can significantly reduce our operating costs, and help the country achieve carbon neutrality. This means better financial and operational resilience, better environmental protection and a better service for our customers.”   

The innovation lies in how sewage sludge is fed into special ‘digesters’ where the biogas-producing process of anaerobic digestion takes place.   

Historically the same amount of sludge was fed in at regular intervals, but specific feeding regimes were designed to increase the biogas production rate between 4pm and 7pm – the peak ‘red period’ when the price for electricity is much higher than at other times.   

For his work, Mauro was awarded the ‘best implementation and best practices paper’ at last year’s WaterEnergyNEXUS conference. The project was also shortlisted in the Most Innovative Use of an Existing Technology category at the 2021 Water Industry Awards in May.   

Dr Jacquetta Lee, of the University of Surrey, said: “Thanks to a long-standing collaboration between the University of Surrey and Thames Water, this research has been a great example of multi-disciplinary research, with immediate impact for Thames Water’s sludge management practices.    

“This recent success demonstrates the validity of scientific research, and the Practitioner Doctorate in Sustainability (PDS) programme at the University of Surrey is the perfect environment for developing and implementing new sustainable practices.    

“Mauro, a researcher on the PDS, has shown that co-development and collaboration between industry and academia can lead to outstanding results and real benefit to industrial partners.”   

The research team also included:  

  • Eve Germain-Cripps – Thames Water’s head of process engineering 
  • Achame Shana  – AD technical expert in Thames Water’s Operational Excellence team  
  • Mark Willcocks  – Thames Water’s energy programme manager  
  • Dr Jacquetta Lee  – of the University of Surrey’s Centre for Environment and Sustainability, Prof Rex Thorpe of the Department of Chemical and Process Engineering and Sabeha Ouki of the Department of Civil and Environmental Engineering 
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