Investigating Dark Fermentation as a Sustainable Organic Waste Management Technology for Producing Biohydrogen From Fruit and Vegetable Waste

Abstract

Fruit and vegetable waste (FVW) is made up of biodegradable organic compounds whose disposal in landfills leads to water and environmental pollution and the emission of lethal greenhouse gases such as methane. Given the high organic content of FVW and its abundant and constant supply, FVW can serve as valuable feedstock for energy production and other value added bio-commodities. Whilst anaerobic digestion is a mature and proven waste management technology, there is need to investigate and develop other environmentally friendly waste treatment technologies. Dark fermentation is a promising alternative waste treatment technology that can be utilized to generate biohydrogen, however, more R&D is still required to improve process efficiency and enhance hydrogen yields. This study investigated the production of biohydrogen via dark fermentation using fruit and vegetable waste as a substrate. To enhance hydrogen production the study applied seed inoculum pre-treatment including heat, alkali, acid, and heat-alkali. The results show that FVW can be used as a feedstock for biohydrogen production and that inoculum pre-treatment enhances hydrogen yields. Acid pre-treatment resulted in the highest hydrogen yield (142, 74 Nml/g VS) and hydrogen content (54%) while heat pre-treatment generated the lowest hydrogen yield (0, 90 Nml/g VS). The hydrogen yields of the pre-treatments tested were substantially different (p<0.001). From highest to lowest, the order of pre-treatment efficacy in terms of hydrogen yield enhancement was acid>heat-alkali>alkali>heat. Under all pre-treatments and controls, the main volatile fatty acid (VFA) formed was valeric acid. The maximum valeric acid fraction observed was 86.1% under acid inoculum pre-treatment.