Spent Mushroom Substrate Hydrolysis and Utilization as Potential Alternative Feedstock for Anaerobic Co-Digestion

Gabriel Vasilakis; Evangelos-Markos Rigos; Nikos Giannakis; Panagiota Diamantopoulou; Seraphim Papanikolaou

doi:10.3390/microorganisms11020532

Spent Mushroom Substrate Hydrolysis and Utilization as Potential Alternative Feedstock for Anaerobic Co-Digestion

Microorganisms. 2023 Feb 20;11(2):532. doi: 10.3390/microorganisms11020532.

Authors

Gabriel Vasilakis¹, Evangelos-Markos Rigos¹, Nikos Giannakis², Panagiota Diamantopoulou³, Seraphim Papanikolaou¹

Affiliations

¹ Laboratory of Food Microbiology and Biotechnology, Department of Food Science and Human Nutrition, Agricultural University of Athens, 11855 Athens, Greece.
² Laboratory of Food Process Engineering, Department of Food Science and Human Nutrition, Agricultural University of Athens, 11855 Athens, Greece.
³ Institute of Technology of Agricultural Products, Hellenic Agricultural Organization "Dimitra", 1 Sofokli Venizelou Str., 14123 Lykovryssi, Greece.

Abstract

Valorization of lignocellulosic biomass, such as Spent Mushroom Substrate (SMS), as an alternative substrate for biogas production could meet the increasing demand for energy. In view of this, the present study aimed at the biotechnological valorization of SMS for biogas production. In the first part of the study, two SMS chemical pretreatment processes were investigated and subsequently combined with thermal treatment of the mentioned waste streams. The acidic chemical hydrolysate derived from the hydrothermal treatment, which yielded in the highest concentration of free sugars (≈36 g/100 g dry SMS, hydrolysis yield ≈75% w/w of holocellulose), was used as a potential feedstock for biomethane production in a laboratory bench-scale improvised digester, and 52 L biogas/kg of volatile solids (VS) containing 65% methane were produced in a 15-day trial of anaerobic digestion. As regards the alkaline hydrolysate, it was like a pulp due to the lignocellulosic matrix disruption, without releasing additional sugars, and the biogas production was delayed for several days. The biogas yield value was 37 L/kg VS, and the methane content was 62%. Based on these results, it can be concluded that SMS can be valorized as an alternative medium employed for anaerobic digestion when pretreated with both chemical and hydrothermal hydrolysis.

Keywords: agro-industrial waste valorization; anaerobic digestion; biofuels; biomethane; chemical hydrolysis; circular economy; hydrothermal process; spent mushroom substrate; waste-to-energy.

Grants and funding

This current investigation has been co-financed by the European Regional Development Fund of the European Union and Greek national funds (European Social Fund—ESF) through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH—CREATE -INNOVATE (project code: Τ1EΔΚ-05027), scientifically coordinated by the Hellenic Agricultural Organization—DEMETER (Institute of Technology of Agricultural Products/Laboratory of Edible Fungi).