UK government highlights hydrogen leakage

The department states that there is an increasing body of evidence that leakage of hydrogen to the atmosphere will have an indirect warming effect on the climate and so should be minimised.

The study used current climate and atmospheric chemistry models to explore the atmospheric impacts of a global hydrogen economy. It modelled atmospheric impacts and calculated the radiative forcing resulting from hydrogen emissions and hydrogen’s global warming potential.

Leakage of hydrogen into the atmosphere will decrease the tropospheric concentration of hydroxyl radicals (OH), the major tropospheric oxidant, and thereby increase the atmospheric lifetime of methane and its impact on climate.

An increase in the atmospheric concentration of hydrogen, assuming no change in other emissions, will increase tropospheric ozone (O3) which is important for both air quality and climate. How it changes in response to the adoption of a hydrogen economy will depend not just on the increase in hydrogen but also on the benefits arising from any associated reductions in the emissions of methane, carbon monoxide, volatile organic compounds and oxides of nitrogen, which will tend to decrease ozone concentrations.

Increases in tropospheric ozone, water vapour and methane, consequent on increases in atmospheric hydrogen, would all tend to increase radiative forcing, partially offsetting the climate benefits of a switch to hydrogen.

The researchers developed a new approach to calculating Global Warming Potentials (GWPs) and propose an estimate of the hydrogen GWP for a 100 year time horizon of 11 ± 5, which is more than 100% larger than previously published calculations. Approximately one third of the GWP arises due to the stratospheric response, which was not considered in previous studies. The majority of uncertainty in the GWP arises from uncertainty in the magnitude of the soil sink for hydrogen.

The report recommends that hydrogen leakage be reduced and that consideration be given to how hydrogen is used to minimise the atmospheric impacts of energy use.

The report was commissioned by BEIS and conducted by the University of Cambridge and the National Centre for Atmospheric Sciences with the University of Reading. It is available here.