Dynamic Control of Anaerobic Digestion for Flexible and Sustainable Generation in the Water Industry

The transition to provision of reliable energy from renewable sources is crucial for a sustainable future. However, the renewable energy sources mostly used are intermittent and therefore are not adequate to cope with the dynamic nature of electricity demand.

In the UK, the water industry currently generates around 800 GWh pa of electricity mainly from Anaerobic Digestion (AD). AD is an established technology for the stabilisation and sterilisation of sewage sludge and the generation of renewable energy (in the form of biogas) from the organic content in human waste. The biogas is used in combined heat and power generation plants that are normally located very close to urban areas and so is an example of locally-sourcing.

A combination of technologies alongside AD constitutes the Thames Water advanced sewage sludge-to-energy generation system. It maximises material and energy recovery from the final by-product of the wastewater treatment according to agreed sustainability criteria, and produces a reliable but steady supply of electricity. Thus, the challenge of this project is to develop a system that can rapidly respond to the dynamic nature of electricity demand, and thereby potentially replace existing non-renewable flexible electricity sources.

The dynamic control of AD could constitute the basis for a modern flexible sewage sludge-to-electricity generation. This research will investigate in which conditions the bacteria in the digesters could produce biogas at varying rates and, optimise the entire sewage sludge electricity generation system in order to maximise its flexibility and ability to meet the dynamic demand.

Overall, this project aims to increase the contribution of renewably sourced electricity in the UK energy mix, by introducing an effective modern sewage sludge-to-electricity system to meet the demands of the UK electricity supply.

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