Co-Processing Lignocellulosic Biomass and Sewage Digestate by Hydrothermal Carbonisation: Influence of Blending on Product Quality

Kiran R. Parmar, Aaron E. Brown, James M. Hammerton, Miller Alonso Camargo-Valero, Louise A. Fletcher and Andrew B. Ross
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Kiran R. Parmar: School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK
Aaron E. Brown: School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK
James M. Hammerton: School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK
Miller Alonso Camargo-Valero: BioResource Systems Research Group, School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK
Louise A. Fletcher: BioResource Systems Research Group, School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK
Andrew B. Ross: School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK

Energies, 2022, vol. 15, issue 4, 1-21

Abstract: Hydrothermal carbonisation (HTC) can be integrated with anaerobic digestion (AD) for the treatment of digestate, resulting in a solid hydrochar or bio-coal and a process water, which can be recirculated back into AD to produce biogas. The properties of digestate-derived hydrochars do not lend themselves to producing high quality bio-coal and blending with lignocellulosic feedstocks can improve its properties. This study investigates the co-processing of sewage sludge (SS) digestate with three lignocellulosic biomass (grass, privet hedge, and woodchip). The calorific value of the resulting bio-coal is increased following co-processing, although feedstock interactions result in non-additive behaviour. The largest increase in calorific value was observed for co-processing with woodchip. There is evidence for non-additive partitioning of metals during co-processing resulting in only moderate improvements in ash chemistry during combustion. Co-processing also effects the composition of process waters, influencing the potential for biogas production. Experimental biomethane potential (BMP) tests indicate that grass clippings are the most suitable co-feedstock for maintaining both calorific value and biogas production. However, above 200 °C, BMP yields appear to decrease, suggesting the process water may become more inhibitory. Co-processing with wood waste and privet hedge produce the higher CV bio-coal but significantly reduced BMP.

Keywords: hydrothermal carbonisation (HTC); digestate; anaerobic digestion (AD); process water; biogas (BMP); bio-coal; ash chemistry; lignocellulosic biomass; blending; combustion (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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