First detection of industrial hydrogen emissions using high precision mobile measurements in ambient air

Projections towards 2050 of the global hydrogen (H2) demand indicate an eight-fold increase in present-day hydrogen consumption. Leakage during production, transport, and consumption therefore presents a large potential for increases in the atmospheric hydrogen burden. Although not a greenhouse gas itself, hydrogen has important indirect climate effects, and the Global Warming Potential of H2 is estimated to be 12.8 times that of CO2. Available technologies to detect hydrogen emissions have been targeted at risk mitigation of industrial facilities, while smaller climate-relevant emissions remain undetected. The latter requires measurement capacity at the parts-per-billion level (ppb). We developed and demonstrated an effective method to detect small hydrogen emissions from industrial installations that combines active AirCore sampling with ppb-precision analysis by gas chromatography. We applied our methodology at a chemical park in the province of Groningen, the Netherlands, where several hydrogen production and storage facilities are concentrated. From a car and an unmanned aerial vehicle, we detected and quantified for the first time small but persistent industrial emissions from leakage and purging across the hydrogen value chain, which include electrolysers, a hydrogen fuelling station, and chemical production plants. Our emission estimates indicate current loss rates up to 4.2% of the estimated production and storage in these facilities. This is sufficiently large to urgently flag the need for monitoring and verification of H2 emissions for the purpose of understanding our climate change trajectory in the 21st century.

Ecosystem fluxes of hydrogen in a mid-latitude forest driven by soil microorganisms and plants

Molecular hydrogen (H₂ ) is an atmospheric trace gas with a large microbe-mediated soil sink, yet cycling of this compound throughout ecosystems is poorly understood. Measurements of the sources and sinks of H₂ in various ecosystems are sparse, resulting in large uncertainties in the global H₂ budget. Constraining the H₂ cycle is critical to understanding its role in atmospheric chemistry and climate. We measured H₂ fluxes at high frequency in a temperate mixed deciduous forest for 15 months using a tower-based flux-gradient approach to determine both the soil-atmosphere and the net ecosystem flux of H₂ . We found that Harvard Forest is a net H₂ sink (-1.4 ± 1.1 kg H₂  ha^-1 ) with soils as the dominant H₂ sink (-2.0 ± 1.0 kg H₂  ha^-1 ) and aboveground canopy emissions as the dominant H₂ source (+0.6 ± 0.8 kg H₂  ha^-1 ). Aboveground emissions of H₂ were an unexpected and substantial component of the ecosystem H₂ flux, reducing net ecosystem uptake by 30% of that calculated from soil uptake alone. Soil uptake was highly seasonal (July maximum, February minimum), positively correlated with soil temperature and negatively correlated with environmental variables relevant to diffusion into soils (i.e., soil moisture, snow depth, snow density). Soil microbial H₂ uptake was correlated with rhizosphere respiration rates (r = 0.8, P < 0.001), and H₂ metabolism yielded up to 2% of the energy gleaned by microbes from carbon substrate respiration. Here, we elucidate key processes controlling the biosphere-atmosphere exchange of H₂ and raise new questions regarding the role of aboveground biomass as a source of atmospheric H₂ and mechanisms linking soil H₂ and carbon cycling. Results from this study should be incorporated into modeling efforts to predict the response of the H₂ soil sink to changes in anthropogenic H₂ emissions and shifting soil conditions with climate and land-use change.

Tropospheric H(2) budget and the response of its soil uptake under the changing environment

Molecular hydrogen (H(2)) is an indirect greenhouse gas present at the trace level in the atmosphere. So far, the sum of its sources and sinks is close to equilibrium, but its large-scale utilization as an alternative energy carrier would alter its atmospheric burden. The magnitude of the emissions associated with a future H(2)-based economy is difficult to predict and remains a matter of debate. Previous attempts to predict the impact that a future H(2)-based economy would exert on tropospheric chemistry were realized by considering a steady rate of microbial-mediated soil uptake, which is currently responsible of ~80% of the tropospheric H(2) losses. Although soil uptake, also known as dry deposition is the most important sink for tropospheric H(2), microorganisms involved in the activity remain elusive. Given that microbial-mediated H(2) soil uptake is influenced by several environmental factors, global change should exert a significant effect on the activity and then, assuming a steady H(2) soil uptake rate for the future may be mistaken. Here, we present an overview of tropospheric H(2) sources and sinks with an emphasis on microbial-mediated soil uptake process. Future researches are proposed to investigate the influence that global change would exert on H(2) dry deposition and to identify microorganisms involved H(2) soil uptake activity.