Improving quantification and understanding of the global H2 soil sink through field and lab based flux measurements

An improved quantification of the soil sink of Hydrogen (H2) gas is required to understand the environmental implications of a future Hydrogen economy and global atmospheric models. Typically, soil microbes utilise H2 as an energy source, but we also have evidence that emission of H2 from soils is also possible via microbial processes. We present new H2 flux data from several field sites and lab studies in which a variety of soils from around the world have been measured from. These sites include agricultural and forest soils from the UK where we have preliminary data of a longer-term measurement campaign. We have developed flux chamber methodology to establish a best practice for measuring H2 flux in soils, which is radically different from typical greenhouse gas protocols. We present our work so far on the development of H2 measurement methodology and on the characterisation of the H2 soil sink in relation to soil physical & chemical properties, vegetation and climate under controlled environment conditions. We also present observations of spatial and temporal soil H2 uptake rates from sites across the UK. We highlight the importance of soil aeration and the physical barriers that strongly interfere with H2 uptake in soils, particularly the influence of high water-filled pore space which should be accounted for in future modelling efforts.