The effects of digestate pyrolysis liquid on the thermophilic anaerobic digestion of sewage sludge — Perspective for a centralized biogas plant using thermal hydrolysis pretreatment. (15th June 2022)

• Record Type: Journal Article
• Authors: Hämäläinen, Anna; Kokko, Marika; Chatterjee, Pritha; Kinnunen, Viljami; Rintala, Jukka
• Is Part Of: Waste management. Volume 147(2022)
• Page Start: 73
• Page End: 82
• Publication Date: 2022-06-15
• Subjects: Anaerobic digestion -- Digested sewage sludge -- Pyrolysis liquid -- Thermal prehydrolysis; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2022.05.013
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Liquid from sewage sludge digestate pyrolysis can be fed to anaerobic digestion (AD). Pyrolysis liquid appeared potentially inhibitory in batch methane assays. Pyrolysis liquid addition did not affect semi-continuous reactor methane yields. Pyrolysis liquid serves as potential diluent to AD-feed at centralized biogas plant. Abstract: The use of pyrolysis process to valorize digestate from anaerobic digestion (AD) of municipal sewage sludge for biochar production was piloted in a central biogas plant. The pyrolysis also generates pyrolysis liquid with high organics and nutrient contents that currently has no value and requires treatment, which could potentially be done in AD. As the pyrolysis liquid may contain inhibitory compounds, we investigated the effects of adding the pyrolysis liquid on AD of sewage sludge and thermal hydrolysis pretreated sewage sludge (THSS) simulating the full-scale centralized biogas plant conditions. In batch assays, the pyrolysis liquid as such did not produce any methane, and the 1% and 5% (v/w) shares suppressed the methane production from THSS by 14–19%, while a smaller decrease in methane production was observed with sewage sludge. However, in the semi-continuous reactor experiments, pyrolysis liquid at a 1% (v/w) share was added in sewage sludge or THSS feed without affecting the methane yields or digestate characteristics. The laboratory results indicated that pyrolysis liquid can be treated in AD, while extrapolating the results to the centralized biogas plant indicated minor increase in the overall methane production and an increased potential for ammonium recovery.