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Open AccessArticle

Hydrogen Production from Coffee Mucilage in Dark Fermentation with Organic Wastes

1
Laboratorio de Mecanización Agrícola, Departamento de Ingeniería Agrícolay de Alimentos, Universidad Nacional de Colombia-Sede Medellín, Carrera 64c # 63-120, Código Postal 050034, Colombia
2
Universidad Nacional de Colombia-Sede Medellín-Escuela de Química-Laboratorio de Procesos Biológicos-Carrera 65 # 59A-110, Medellín, Código Postal 050034, Colombia
3
Department of Biology, Hood College, 401 Rosemont Avenue, Frederick, MD 21701, USA
*
Author to whom correspondence should be addressed.
Authors contributed equally to the study.
Energies 2019, 12(1), 71; https://doi.org/10.3390/en12010071
Received: 5 November 2018 / Revised: 26 November 2018 / Accepted: 27 November 2018 / Published: 27 December 2018
(This article belongs to the Special Issue Biomass Processing for Biofuels, Bioenergy and Chemicals)
One of primary issues in the coffee manufacturing industry is the production of large amounts of undesirable residues, which include the pericarp (outer skin), pulp (outer mesocarp), parchment (endocarp), silver-skin (epidermis) and mucilage (inner mesocarp) that cause environmental problems due to toxic molecules contained therein. This study evaluated the optimal hydrogen production from coffee mucilage combined with organic wastes (wholesale market garbage) in a dark fermentation process. The supplementation of organic wastes offered appropriate carbon and nitrogen sources with further nutrients; it was positively effective in achieving cumulative hydrogen production. Three different ratios of coffee mucilage and organic wastes (8:2, 5:5, and 2:8) were tested in 30 L bioreactors using two-level factorial design experiments. The highest cumulative hydrogen volume of 25.9 L was gained for an 8:2 ratio (coffee mucilage: organic wastes) after 72 h, which corresponded to 1.295 L hydrogen/L substrates (0.248 mol hydrogen/mol hexose). Biochemical identification of microorganisms found that seven microorganisms were involved in the hydrogen metabolism. Further studies of anaerobic fermentative digestion with each isolated pure bacterium under similar experimental conditions reached a lower final hydrogen yield (up to 9.3 L) than the result from the non-isolated sample (25.9 L). Interestingly, however, co-cultivation of two identified microorganisms (Kocuria kristinae and Brevibacillus laterosporus), who were relatively highly associated with hydrogen production, gave a higher yield (14.7 L) than single bacterium inoculum but lower than that of the non-isolated tests. This work confirms that the re-utilization of coffee mucilage combined with organic wastes is practical for hydrogen fermentation in anaerobic conditions, and it would be influenced by the bacterial consortium involved. View Full-Text
Keywords: hydrogen; coffee mucilage; organic wastes; dark fermentation; anaerobic digestion hydrogen; coffee mucilage; organic wastes; dark fermentation; anaerobic digestion
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MDPI and ACS Style

Cárdenas, E.L.M.; Zapata-Zapata, A.D.; Kim, D. Hydrogen Production from Coffee Mucilage in Dark Fermentation with Organic Wastes. Energies 2019, 12, 71.

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