Understanding the benefits and risks of the hydrogen economy: the HYDRA project
Authors: Urgnani Rossella , Ferreras Alonso Noelia , Bellucci Alessio , Wild Oliver , Panopoulos Kyriakos , Santarelli Massimo , Poinsel Nathanael , Vicini Isella 
Published: March 2024

The European Green Deal target of zero emissions by 2050, boosted by the energy crisis due to the Russian-Ukranian conflict, put decarbonisation at the forefront of policymakers&#8217; and industries&#8217; development plans. Hydrogen, especially if produced by renewable energy sources, is considered one of the main candidates in the ongoing energy transition. The hydrogen economy is still in its early stages, due to the high cost of technologies, production, and infrastructure, but the electrolyser capacity installed in 2023 doubled 2022 levels (IEA report, 2023), with clear signs of increasing investments in this sector. However, large-scale diffusion of hydrogen technologies could negatively impact climate because of the increase in H2 emissions (through leakages or other mechanisms) to the atmosphere and its interactions with other gases. Hydrogen interacts with the oxidative cycles of CH4, NOx, and CO, affecting natural GHG-removing mechanisms. In addition, an increase in atmospheric hydrogen could alter stratospheric levels of ozone and water vapour. Increasing H2 emissions may result in an increase in global radiative forcing, even if H2 replaces a proportion of fossil fuel use. However, quantification of these impacts remains uncertain and depends on the development and uptake of different hydrogen technologies. The HYDRA project, funded by the European Commission under the Horizon Europe program, officially started on November 1st, 2023, and aims to evaluate the benefits and the potential risks associated with the hydrogen economy. It starts with the analysis of policies and markets to quantify the potential diffusion of hydrogen technologies in the mid-to-long term and the associated emissions of H2 and other gases (e.g., CH4, H2O, NOX, methanol, NH3). Using these data, HYDRA will simulate the impacts of the integration of hydrogen in the energy sector using WILIAM, an Integrated Assessment Model accounting for interactions between society, economy, and the environment, which will produce a range of energy, land, and emission scenarios. The FRSGC/UCI Chemical Transport Model will then be used to quantify global and regional impacts on O3, CH4, NOX, VOC, CO, and other oxidants, estimating the uncertainty in the important soil sink of hydrogen. The role of H2 in influencing stratospheric water vapour, ozone, and nitrous oxide (N2O) will be determined with the SLIMCAT and UKCA models. The changes in atmospheric composition from these simulations will be used to estimate the effective radiative forcing associated with H2 emissions and perform future climate projections, using the EC-Earth global climate model. Finally, since hydrogen-air mixes are highly inflammable, HYDRA will develop a new leakage detection/quantification monitoring system to make H2 technologies safer. The overall benefits and risks associated with a future hydrogen economy will be evaluated from a sustainable perspective, from changes in mean climate conditions to impacts on society and environment. HYDRA is fully committed to finding sustainable solutions for the development of the hydrogen economy, and to proposing mitigation strategies and guidelines for policymakers at the end of the 4-year project.