Environmental impact and water footprint of biofuel production from macro-algae biomass based on life cycle assessment

Algae, especially macro-algae, are a promising feedstock to produce renewable biofuel, which raises many interests in utilization processes. Focusing on three utilization processes using Enteromorpha clathrata (EN, a kind of macro-algae) as feedstock to produce biofuel, this study evaluates their environmental impacts and water resource consumption. It was found that, among three utilization scenarios, the pyrolysis catalyzed by EN self-derived carbon shows the least global warming potential (8823.73 kg ${\text{CO}}_2$ eq/t biofuel) and water resource consumption (206.382 m³/t biofuel). The oil production system takes into account operations such as bio-oil hydrogenation upgrading and synthesis gas hydrogen production to enhance system efficiency. However, it was found that the hydrogen was meted by green hydrogen form renewable electricity and the pyrolytic gas directly combusted, GWP and WCP could be reduced by 27 % and 22 % at most, respectively. To comprehensively evaluate the impact on the environment and water consumption, cultivation and raw material processing are carried out separately. The results indicate that Jiangsu Province is the most suitable region for EN oil production. The whole life cycle assessment results of this paper can be used as a reference for the subsequent algal oil production program in China.