CO 2 Emission Avoidance in Organic Waste Management: Co-Digestion of Brewery’s Spent Grain Pulp with Lemna minor

Alberto Maria Gambelli (), Jessica Di Mario, Dario Priolo, Daniele Del Buono and Giovanni Gigliotti
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Alberto Maria Gambelli: Civil and Environmental Engineering Department, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy
Jessica Di Mario: Civil and Environmental Engineering Department, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy
Dario Priolo: Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, 06121 Perugia, Italy
Daniele Del Buono: Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, 06121 Perugia, Italy
Giovanni Gigliotti: Civil and Environmental Engineering Department, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy

Sustainability, 2025, vol. 17, issue 22, 1-16

Abstract: This study focuses on biogas production within lab-scale semi-batch bioreactors using agro-industrial wastes and dry biomass of an invasive aquatic species. In particular, the primary objective is to increase the yield of anaerobic digestion processes, with a specific focus on reducing CO 2 emissions associated with the degradation of biomass, by co-digesting different raw biomasses and agro-industrial wastes. In detail, the experiments concerned the pulp of Brewery’s Spent Grain (BSGp), consisting of the residual of Brewery’s Spent Grain after fiber deconstruction with ionic liquids–based treatment, and Lemna minor L. (LM). The two biomasses were studied separately and then co-digested. Co-digestion was carried out using a 1:1 (VS basis) mixture of Lemna minor and Brewery’s Spent Grain pulp. Due to the lack of organic nitrogen, BSGp showed low biogas production if compared with untreated BSG (1.14 × 10 −3 vs. 1.71 × 10 −3 Nm 3 /gVS). Differently, LM has a high nitrogen content and, when digested alone, produced 9.79 × 10 −4 Nm 3 /gVS. The co-digestion tests allowed us to reach the highest performance: 2.94 × 10 −3 Nm 3 /gVS. In terms of bioenergy production, the two biomasses showed high synergy when used in co-digestion. The amount of energy produced was calculated using a lower heating value (LHV) of CH 4 equal to 52 MJ. The results showed that co-digestion yielded 64.9 ± 0.6 MJ/kgVS, followed by BSG (43.3 ± 5.3 MJ/kgVS), BSGp (25.6 ± 0.3 MJ/kgVS), and LM (19.3 ± 1.0 MJ/kgVS). In addition, in terms of CO 2 avoided, the following results were achieved: 0.38–0.40 gCO 2 /gVS with BSGp, 0.73–0.8 gCO 2 /gVS with LM. Conversely, co-digestion tests allowed for the avoidance of 1.68–1.91 gCO 2 /gVS. In conclusion, co-digesting BSGp with Lemna minor yields more methane and less CO 2 per unit processed, providing an effective way to convert readily available waste and biomass into bioenergy.

Keywords: biogas/biomethane production; co-digestion; bioenergy; reduction of CO 2 emissions (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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