For many years, the water industry has used the anaerobic digestion (AD) process to convert sewage sludge into fertilisers for farmland and biogas to generate heat and renewable electricity.
However, larger volumes of waste caused by a growing population, more stringent environmental targets and limited infrastructure mean that there is a growing need to make this process more efficient.
Yorkshire Water and the University of York, with funding from the Royal Society, are working on a research project to transform Yorkshire Water’s approach to AD.
The aim of the project is to increase the efficiency of the AD process and convert more solid material into biogas. This would mean more sewage sludge could be processed using the same facilities, reducing the need to build more infrastructure. It would also boost levels of renewable energy production, generate a higher-quality fertiliser product, and provide customers with value for money.
Significant investment has been made in state-of-the-art experimental facilities to address critical research gaps relating to AD.
This includes a new set of 60 five-litre automatically fed, temperature-controlled anaerobic digesters - known as System-60 - installed at the University’s Department of Biology, as well as a pilot-scale digestion facility at Yorkshire Water’s nearby wastewater treatment works in Naburn.
In combination, these facilities will provide new insights into the microbial communities that drive digester performance. System-60 will be used to screen conditions and the pilot rig at Naburn will be used to demonstrate the benefits at a larger scale to build a case for operational changes across Yorkshire Water’s digester fleet.
University of York’s role
The project involves collaboration across the University. Custom-made sensor equipment has been designed and built by the Biology Mechanical and Electronics Workshop and specially developed software has been written by undergraduates from the Department of Computer Science.
University researchers will be managing System-60 on campus, in addition to monitoring Yorkshire Water’s recently refurbished Naburn pilot AD facility.
Professor James Chong, project lead from the Department of Biology said: “The water industry has recognised that what ends up in the sewer is a bioresource. Data from System-60 and the pilot rig at Naburn, paired with our state-of-the-art analytical facilities, should give us a clearer picture of the microbiological basis of AD. Yorkshire Water has demonstrated a long-term vision in the potential of AD by investing in these facilities and by providing us with exceptional access to their AD operations.”
Richard Flint, CEO, at Yorkshire Water said: “AD is hugely important to Yorkshire Water and its customers. One of the big challenges we’re going to have over the next few years is as the population grows we will have more waste to treat. We need to find more efficient ways to keep the prices of our bills low but also to generate energy to power our business and of course deal with one of our major challenges which is about becoming carbon neutral as a company by 2030. The work with the University of York is really important because what it allows us to do is really delve into the basics of anaerobic digestion and really get down to the scientific level.”
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