Life cycle environmental balance and greenhouse gas mitigation potential of micro-hydropower energy recovery in the water industry

Micro-hydropower (MHP) presents new opportunities to generate electricity from within existing water infrastructure. This paper quantifies the environmental impacts of electricity generation from three MHP case studies (15-140 kW) in the water industry, using a life cycle assessment approach. Environmental burdens were calculated per kWh electricity generated over nominal turbine operational lifespans. Compared with marginal UK grid electricity generation in combined cycle turbine natural gas power plants, normalised life cycle environmental burdens for MHP electricity were reduced by: >99% for global warming potential (GWP); >98% for fossil resource depletion potential; >93% for acidification potential; 50-62% for human toxicity potential. However, the burden for abiotic resource depletion potential was 251-353% higher for MHP than marginal grid-electricity. Different quantities of raw materials and installation practices led to a range in GWP burdens from 2.14 to 4.36 g CO₂ eq./kWh. One case benefitted from very low site preparation requirements while others required substantial excavation works and material quantities. Carbon payback times ranged from 0.16 to 0.31 years, extending to 0.19-0.40 years for worst-case scenarios examined as part of a sensitivity analysis. The carbon payback period for future MHP installations was estimated to increase by 1% annually, as the carbon intensity of marginal grid electricity is predicted to decline. This study demonstrates that MHP installations in the water industry have a strongly positive environmental balance.