A comparative environmental impact analysis of H2O electrolysis technologies under different energy scenarios

Both scientific community and politic institutions frequently stress the crucial role of energy and renewables as key-asset to reduce climate change and support the achievement of long-term sustainable development goals. Hydrogen supplying to industrial users is currently the major hydrogen business worldwide and the demand for hydrogen is almost entirely supplied from fossil fuels. In such a context, the use of hydrogen as energy carrier represents a sustainable pathway towards the energy transition and the decarbonization of the most energy-intensive sectors. The H2O electrolysis technologies cope the challenges related to the balance of fluctuating electricity generation from renewables as backup power and energy storage. The three main H2O electrolysis technologies commercially available are the alkaline electrolysis cell (AE/AEC), polymer electrolyte membrane electrolysis cell (PEM/PEMEC), and solid oxide electrolysis cell (SOE/SOEC). Several studies analyze the environmental impacts of the H2O electrolysis technologies considering their main components and manufacturing processes in a life cycle perspective. Moreover, the hydrogen production process is often investigated comparing these technologies under different energy scenarios. Starting from the Life-Cycle-Impact-Assessment (LCIA) results in literature, this paper tries to contribute to this research stream focusing on the Global Warming Potential (GWP) of the low-temperature electrolysis technologies (AEC and PEM), by evaluating the effect of different Italian energy policies on the hydrogen production. The comparative analysis includes the impacts related to the stacks and to the operation phase of producing hydrogen, while those of Balance of Plant (BoP) are not included in the system boundaries. Overall, based on the results of this paper, PEM technology has a lower GWP than AEC. Moreover, future scenarios with a high share of renewables in the energy mix significantly reduce the GWP related with the operation phase of these electrolysis technologies.