Abstract
The UK is a global leader in the decarbonisation of its electricity grid to meet zero-carbon targets. However, the main renewable sources, wind, and solar are intermittent and weather dependent. Therefore, other flexible sources need to be able to rapidly increase generation when needed. In this context, electricity generation from anaerobic digestion (AD) of sewage sludge has been traditionally operated as a baseload provider (i.e. steady biogas production rate and electrical output). This work challenges such a traditional approach and aims to investigate how the sewage sludge-to-electricity generation system can provide flexible renewable power generation. Specific feeding regimes were designed following an analysis of the power grid balancing services, to increase the biogas production rate when needed. These feeding regimes were tested at incremental experimental scales. Multiple AD conditions were tested at a pilot scale (50 l) in a controlled environment, which proved the potential economic and environmental benefits. Then, the most challenging conditions were tested at a demonstration scale (18 m3), which confirmed the results obtained at the pilot scale in a relevant operational environment. This research work proved that by implementing an appropriate control of AD, the process can produce more biogas in peak periods to generate electricity when the grid’s prices and carbon emissions peak, unlocking the potential for full-scale implementation.