Exergoenvironmental assessment of hydrogen water footprint via steam reforming in Brazil

Abstract

Due to the major role played by fossil fuels in the current hydrogen production scenario, environmentally friendly pathways are being considered. These pathways can use a wide variety of raw materials, providing flexibility for hydrogen production regardless of geographical, economic and political aspects. However, the choice for a given process and feedstock must ensure its environmental viability, which can be evaluated through several indicators such as carbon, land and water footprints. In this study, one of the most promising hydrogen production processes, namely steam reforming, was assessed for the Brazilian scenario from a water consumption point of view. The systems were computationally simulated using Aspen HYSYS V11™ software for hydrogen production from natural gas, bioethanol and glycerol – all of which are readily available for use in Brazil, and an exergy analysis was applied alongside known and estimated water footprint indicators. Steam methane reforming (SMR) presented the lowest water footprint per kg of H2 (0.257 m³/kgH2), followed by glycerol (0.768 m³/kgH2) and bioethanol reforming (9.651 m³/kgH2). The exergoenvironmental analysis shows that the main bottlenecks identified are related to exergy destruction in the burners (52.46–57.32%), reformers (2.48–21.72%) and heat exchangers (19.45–32.61%), but globally, exergoenvironmental indicators showed that steam reforming of the presented feedstock can be an alternative to be explored in the context of water resources preservation.