Sustainability evaluation of H2 production from sheep tallow by combining Emergy and environmental life cycle assessment

In the aim to reach low or net zero emissions energy systems by 2050, the transition toward more sustainable energy carriers seems crucial. H2 is gradually gaining attention as a promising alternative solution for future energy supply. The main purpose of this study is to investigate the sustainability of H2 generated from sheep tallow. To this end, a combination of life cycle assessment and Emergy analysis was applied. Different impact categories, following ReCiPe method, cumulative energy demand were calculated for the evaluation of the system environmental performances. Emergy comprehensively evaluated H2 production sustainability, through a set of indicators such as transformity, environmental loading ratio, percentage of renewability, Emergy yield ratio, Emergy investment ratio and Emergy sustainability index. The life cycle assessment results show that the thermal energy is the main contributor to the selected environmental impact categories. The net energy ratio of the system is approximately 2.5. Therefore, the H2 system presents a net energy gain. Emergy indices indicate that H2 transformity is higher than that of many other energy carriers. Also, the environmental loading ratio calculated is 17.26, indicating that the activities of the process increase the pressure on the environment. The environmental sustainability index is estimated to be 0.06 which shows that the investigated system is unsustainable from an emergetic point of view.