A cascade biorefinery for grape marc: Recovery of materials and energy through thermochemical and biochemical processes

Gianluigi Farru; Giovanna Cappai; Alessandra Carucci; Giorgia De Gioannis; Fabiano Asunis; Stefano Milia; Aldo Muntoni; Matteo Perra; Angela Serpe

doi:10.1016/j.scitotenv.2022.157464

A cascade biorefinery for grape marc: Recovery of materials and energy through thermochemical and biochemical processes

Sci Total Environ. 2022 Nov 10:846:157464. doi: 10.1016/j.scitotenv.2022.157464. Epub 2022 Jul 19.

Authors

Gianluigi Farru¹, Giovanna Cappai², Alessandra Carucci², Giorgia De Gioannis², Fabiano Asunis³, Stefano Milia⁴, Aldo Muntoni², Matteo Perra⁵, Angela Serpe²

Affiliations

¹ DICAAR - Department of Civil - Environmental Engineering and Architecture, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy. Electronic address: gianluigi.farru@unica.it.
² DICAAR - Department of Civil - Environmental Engineering and Architecture, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy; IGAG-CNR - Institute of Environmental Geology and Geoengineering, National Research Council, Via Marengo 2, 09123 Cagliari, Italy.
³ DICAAR - Department of Civil - Environmental Engineering and Architecture, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy.
⁴ IGAG-CNR - Institute of Environmental Geology and Geoengineering, National Research Council, Via Marengo 2, 09123 Cagliari, Italy.
⁵ Department of Life and Environmental Sciences, University of Cagliari, Via Ospedale 72, Cagliari 09124, Italy.

PMID: 35868380
DOI: 10.1016/j.scitotenv.2022.157464

Abstract

The agro-industrial sector makes a high contribution to greenhouse gas emissions; therefore, proper waste management is crucial to reduce the carbon footprint of the food chain. Hydrothermal carbonization (HTC) is a promising and flexible thermochemical process for converting organic materials into energy and added-value products that can be used in different applications. In this work, grape marc residues before and after an extraction process for recovering polyphenols were hydrothermally treated at 220 °C for 1 h. The resulting hydrochar and process water were investigated to test an innovative cascade approach aimed at a multiple product and energy recovery based on the integration of HTC with anaerobic digestion. The results show that this biorefinery approach applied to grape marc could allow to diversify and integrate its potential valorisation options. The produced hydrochars possess an increased fixed carbon content compared to the feedstock (up to +70 %) and, therefore, can be used in soil, immobilizing carbon in a stable form and partially replacing peat in growing media (up to 5 % in case of hydrochar from grape marc after extraction), saving the consumption of this natural substrate. In addition, energy can be recovered from both hydrochar by combustion and from process water through anaerobic digestion to produce biogas. Hydrochars show good properties as solid fuel similar to lignite, with an energy content of around 27 MJ kg^-1 (+30 % compared to the feedstock). The anaerobic digestion of the process water allowed obtaining up to 137 mL of biomethane per gram of fed COD. Finally, while HTC process waters are suitable for biological treatment, attention must be paid to the presence of inhibiting compounds that induce acute toxic effects in aerobic conditions. The proposed approach is consistent with the principles of circular economy and could increase the overall sustainability and resilience of the agro-industrial sector.

Keywords: Biofuel; Biomethane; Biorefinery; Hydrothermal Carbonization; Soil Amendment.

MeSH terms

Biochemical Phenomena*
Carbon
Soil
Temperature
Vitis*
Water

Substances

Soil
Water
Carbon