Assessing the water footprint in the green hydrogen production using a Liquid Organic Hydrogen Carrier: a case study in Uruguay

Main Presenter:    Axel Ríos 

Co-Authors:   Castelló Elena     Goycoechea Nicolás      Corengia Mariana                                    

Decarbonizing the energy production stands as a paramount objective of today´s society. The utilization of “green hydrogen” has the potential to be an important contributor towards this goal . Green hydrogen production, achieved by splitting water into oxygen and hydrogen using electrolysis, demands only two components, water and renewable electricity. Nevertheless, it requires substantial quantities of extremely high purity water, prompting a crucial examination of water consumption and environmental impacts in water reservoirs to ensure process sustainability. While sustainability studies on green hydrogen production often emphasize the carbon footprint, the water aspect is frequently overlooked [1].
To comprehensively evaluate the water component of sustainability, this study employs a water footprint analysis, both from a Life Cycle Assessment (LCA) and the Water Footprint Network points of view. Although the utilization of LCA is the preferred method, currently it is not the prevalent one in Latin America, a region of particular interest for its important water reservoirs and abundance of renewable energy, which makes it a key player in the future of green hydrogen production processes [2].
This work utilizes the produced kg of H2 as its functional unit and focuses on a proposed green hydrogen production plant in Uruguay as a case study, analyzing the water footprint of the production process, distinguishing its environmental impacts according to the water reservoirs used. The scope of the study includes the production process utilizing alkaline electrolysis after electrical generation, concluding with hydrogen storage using a liquid organic hydrogen carrier (LOHC).
Different conditions for the electrolyzer were studied, with varying operating pressures from 1 to 50 bar and temperatures between 60 °C and 80 °C. One key aspect to consider is that the amount of water lost in oxygen flow increases between 2 and 4 times with higher temperatures and between 62 and 93 times at lower pressures.
One of the most important conclusions of this work is that the water consumption directly associated with the electrolysis process is of a similar magnitude, and even inferior to the water used in industrial services, mainly cooling. Stoichiometric water consumption representing between 20 % and 23 % of total water consumption.

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