Effects of carbon-based conductive materials on semi-continuous anaerobic co-digestion of organic fraction of municipal solid waste and waste activated sludge

Filippo Fazzino; Patrizia Frontera; Angela Malara; Altea Pedullà; Paolo S Calabrò

doi:10.1016/j.chemosphere.2024.142077

Effects of carbon-based conductive materials on semi-continuous anaerobic co-digestion of organic fraction of municipal solid waste and waste activated sludge

Chemosphere. 2024 Apr 19:357:142077. doi: 10.1016/j.chemosphere.2024.142077. Online ahead of print.

Authors

Filippo Fazzino¹, Patrizia Frontera², Angela Malara², Altea Pedullà², Paolo S Calabrò³

Affiliations

¹ Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria, 6, Catania, Italy.
² Department of Civil, Energy, Environmental and Materials Engineering, Mediterranea University of Reggio Calabria, Via Zehender, loc. Feo di Vito, 89122, Reggio Calabria, Italy.
³ Department of Civil, Energy, Environmental and Materials Engineering, Mediterranea University of Reggio Calabria, Via Zehender, loc. Feo di Vito, 89122, Reggio Calabria, Italy. Electronic address: paolo.calabro@unirc.it.

PMID: 38643843
DOI: 10.1016/j.chemosphere.2024.142077

Abstract

Organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS) are the most produced organic waste streams in urban centres. Their anaerobic co-digestion (AcoD) allows to generate methane (CH₄) and digestate employable as renewable energy source and soil amendment, respectively, fully in accordance with circular bioeconomy principles. However, the widespread adoption of such technology is limited by relatively low CH₄ yields that fail to bridge the gap between benefits and costs. Among strategies to boost AcoD of OFMSW and WAS, use of conductive materials (CMs) to promote interspecies electron transfer has gained increasing attention. This paper presents one of the few experimental attempts of investigating the effects of four different carbon(C)-based CMs (i.e., granular activated carbon - GAC, graphite - GR, graphene oxide - GO, and carbon nanotubes - CNTs) separately added in semi-continuous AcoD of OFMSW and thickened WAS. The presence of C-based CMs has been observed to improve CH₄ yield of the control process. Specifically, after 63 days of operation (concentrations of GAC and GR of 10.0 g/L and of GO and CNTs of 0.2 g/L), 0.186 NL/g_VS, 0.191 NL/g_VS, 0.203 NL/g_VS, and 0.195 NL/g_VS of CH₄ were produced in reactors supplemented with GAC, GR, GO, and CNTs, respectively, compared to 0.177 NL/g_VS produced in the control process. Likewise, at the end of the test (i.e., after 105 days at concentrations of C-based CMs half of the initial ones), CH₄ yields were 0.193 NL/g_VS, 0.201 NL/g_VS, 0.211 NL/g_VS, and 0.206 NL/g_VS in reactors supplemented with GAC, GR, GO, and CNTs, respectively, compared to 0.186 NL/g_VS of the control process. Especially with regard to GR, GO, and CNTs, results obtained in the present study represent a significant advance of the knowledge on the effects of such C-based CMs to realistic and scalable AD process conditions respect to previous literature.

Keywords: Anaerobic co-digestion; Biomethane; Carbon-based conductive materials; Circular bioeconomy; Organic fraction of municipal solid waste; Waste activated sludge.