Coupling Hydrothermal Carbonization with Anaerobic Digestion for Sewage Sludge Treatment: Influence of HTC Liquor and Hydrochar on Biomethane Production

Roberta Ferrentino, Fabio Merzari, Luca Fiori and Gianni Andreottola
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Roberta Ferrentino: Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123 Trento, Italy
Fabio Merzari: Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123 Trento, Italy
Luca Fiori: Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123 Trento, Italy
Gianni Andreottola: Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123 Trento, Italy

Energies, 2020, vol. 13, issue 23, 1-19

Abstract: The present study addresses the coupling of hydrothermal carbonization (HTC) with anaerobic digestion (AD) in wastewater treatment plants. The improvement in biomethane production due to the recycling back to the anaerobic digester of HTC liquor and hydrochar generated from digested sludge is investigated and proved. Mixtures of different compositions of HTC liquor and hydrochar, as well as individual substrates, were tested. The biomethane yield reached 102 ± 3 mL CH 4 g −1 COD when the HTC liquor was cycled back to the AD and treated together with primary and secondary sludge. Thus, the biomethane production was almost doubled compared to that of the AD of primary and secondary sludge (55 ± 20 mL CH 4 g −1 COD). The benefit is even more significant when both the HTC liquor and the hydrochar were fed to the AD of primary and secondary sludge. The biomethane yield increased up to 187 ± 18 mL CH 4 g −1 COD when 45% of hydrochar, with respect to the total feedstock, was added. These results highlight the improvement that the HTC process can bring to AD, enhancing biomethane production and promoting a sustainable solution for the treatment of the HTC liquor and possibly the hydrochar itself.

Keywords: sewage sludge; hydrothermal carbonization; hydrochar; HTC liquor; anaerobic digestion; biochemical methane potential; biomethane (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: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (8)

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