A bio-augmented system with Methylosarcina sp. LC-4 immobilized on bio-carriers: Towards an integrated approach to mitigate and valorize methane emissions from landfills to biodiesel

• Published in: Chemosphere (Oxford) 2023-11, Vol.341, p.139992-139992, Article 139992
• Main Authors: Sana, Nivedita, Arnepalli, Dali Naidu, Krishnan, Chandraraj
• Format: Article
• Language: English
• Subjects: Alternate daily cover; Bio-augmented system; Biodiesel; bioeconomics; biomass; fatty acid methyl esters; greenhouses; landfills; methane; Methane elimination capacity; Methane mitigation; methanotrophs; Methylosarcina; oxidation; perlite; surface area; Valorization; value added; vermiculite; water holding capacity
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2023.139992

Bio-augmented systems based on methanotrophs are indispensable in curbing anthropogenic methane emissions from engineered landfills or dumpsites to curtail rising levels of greenhouse gases. Using a defined methanotroph culture immobilized on an inert material-based bio-carrier makes it possible to harness these methane emissions for creating value-added products, thus contributing to the circular bio-economy. The methane oxidation capacity of the model methanotroph Methylosarcina sp. LC-4, a prospective organism for biodiesel production using methane present in landfill gas, immobilized on several inert bio-carriers, was evaluated to identify a bio-carrier that provided optimum conditions for the process. Among the several bio-carriers evaluated, perlite and vermiculite were selected due to their high specific surface area and superior water-holding capacity, which result in the retention of nutrients and biomass and higher methane elimination capacity. While perlite showed high biomass holding capacity and methane transport, vermiculite supported a high growth of methanotrophs. LC-4 immobilized on perlite and vermiculite as the bio-carrier showed maximum methane elimination capacity (MEC) of 291.3 g m−2 day−1 and 155.5 g m−2 day−1, respectively. The low bed height of only 0.13 m and a short start-up period of 2–4 days are promising for use as alternate daily cover in a landfill. The recovered biomass had 12% (w/w) fatty acid methyl ester (FAME), with a high fraction of (∼85%) of C14–C18 saturated and monounsaturated fatty acids, suitable for biodiesel production. The combination of perlite and vermiculite increased MEC and FAME content levels. The current study demonstrated a new bio-augmented system designed with a pure methanotroph for methane elimination with a short start-up time and the valorization of the assimilated methane. [Display omitted] •Bio-augmented systems were screened to mitigate methane emissions from landfills.•Perlite and vermiculite provided the best conditions for methane mitigation.•High methane removal with a bed height of 0.13 m and a start-up period of 2–4 days•The recovered biomass had up to 12% (w/w) fatty acid methyl ester (FAME).•Suitable as daily cover in engineered landfill with biodiesel as a byproduct.