Evaluation of the life cycle of hydrothermally carbonized biomass for energy and horticulture application

Abstract

Hydrothermal carbonization (HTC) is a promising method to process high moisture biomass into biofuel/biomaterial. The environmental benefits of biomass depend on the processing methods and its end-use. Although life cycle assessment (LCA) of HTC of wet biomass has been conducted, co-processing of peat moss with agricultural biomass (miscanthus) is yet to be reported. This study evaluates the environmental performance of hydrothermally carbonized biomass (peat moss, miscanthus, and a blend of the two) used for energy (S3, S5, S7) or soil amendment (S2, S4, S6, S8) and compared with untreated biomass (peat moss left on-site: S1; peat moss used for soil amendment: S2) to determine the most viable pathway of biomass. Hydrochar produced from miscanthus had a lower global warming potential (GWP) compared with the hydrochar from peat moss or their blend; however, other impact categories were observed to be greater. The environmental impacts from the life cycle of biomass depend on their life cycle pathways. The highest GWP was observed in the case of peat moss used for horticulture application (S2) followed by S3, S5, S4, S6, S7, S8 and S1. Hydrochar used in soil amendment was more environmentally benign than the energy application, but the benefits were dependent on the decomposition rate of biomass. Additionally, HTC process required a considerable amount of water even it can process high moisture biomass. Renewable energy and agricultural policy may be needed to encourage hydrochar use/production/integration into soil amendment and energy application in rural communities.