Heat pumps could reduce biogas carbon footprint more than a third, claims research
17 Jan 2023
Using air-source heat pumps for anaerobic digestion could slash the carbon footprint of the process by 36%, new research by the University of Glasgow and University College London asserts.
The scientists say their findings could help support efforts to decarbonise national electricity grids and enable remote communities to produce their own low-carbon power locally.
Anaerobic digestion uses microorganisms in oxygen-free conditions to break down biodegradable materials such as food waste and sewage sludge to release biogas that can be burned to turn turbines, generating low-carbon electricity.
Bioreactors are then employed to maintain optimal temperature during anaerobic digestion to maximise the amount of biogas generated.
The research, ‘Integration of Anaerobic Digestion with Heat Pump: Machine Learning-based Technical and Environmental Assessment’, published in Bioresource Technology, involved the creation of a computer model of the thermodynamics of heat pumps. This was coupled with machine learning-based anaerobic digestion modelling to train the new system using a database of existing research.
This was tested with actual data to check accuracy before comparing the carbon footprint of a heat pump-based system with a natural gas-based one over their life cycle. The results suggested that the heat pump would emit significantly less carbon when processing food waste and sewage sludge for biogas.
The modelled carbon reduction attained up to 28.1% in an anaerobic digestion process maintained at a temperature of 55°C. At a lower temperature of 37.5°C, the carbon footprint of the process was reduced even further to a maximum of 36.1%.
Co-author Dr Siming You, from Glasgow University’s James Watt School of Engineering, said harnessing gas from waste for power production instead of letting it decay naturally, would advance the circular, net-zero economy to reduce the impact of climate change.
“That could help inform future planning for municipal waste management facilities to help reduce their carbon footprints. It could also underpin the development of future bioreactors which could be used in remote communities to help people turn their waste into biogas,” said You.
“That kind of decentralised waste recycling could go a long way to helping people produce their own local source of electricity. The research is also part of a larger effort to decarbonise water and wastewater treatment in rural communities.”
The research was supported by funding from the Engineering and Physical Sciences Research Council (EPSRC), the Supergen Bioenergy Hub and the Royal Society.
