Lifecycle environmental impacts of biochar in Belgium: The influence of biochar feedstocks, production temperatures, and applications

Abstract

This study aims to support decision-making on biochar deployment in Flanders, Belgium by assessing whether diverting biomass to biochar production yields environmental benefits on a lifecycle basis, and by identifying the most favorable combinations of feedstock, production temperature, and application. Using a consequential life cycle assessment (LCA), we investigate biochars produced at 450 °C and 600 °C from the woody fraction of green waste and chicken manure. Biochar applications are direct soil amendment and cascading use, where biochar is first used to enhance anaerobic digestion. To the best of our knowledge, this is the first consequential LCA that simultaneously compares biochar’s environmental impact across pyrolysis temperatures, feedstocks, and applications. For both feedstocks, no system outperforms all others in all impact categories, so the preferred option depends on the impact category. Pyrolysis, especially with cascading use, is generally preferred for global warming and fossil resource scarcity, and frequently for terrestrial acidification and marine eutrophication. Reference systems generally show lower toxicity impacts, although toxicity-related results should be interpreted with caution due to modeling simplifications. Overall, chicken manure systems outperform green waste in most categories. In the current case study, with its specific modeling assumptions and system boundaries, the environmental impacts are driven more by market substitution effects and carbon sequestration than by biochar’s field effects. This study shows the potential desirability of biochar production and application in specific contexts.