Waste to Renewable Energy: A Sustainable and Green Approach Towards Production of Biohydrogen by Acidogenic Fermentation

TLDR: In this article, the evaluation of fermentative H2-generating processes utilizing wastewater as substrate and mixed culture as biocatalyst is presented, and a particular insight was also laid on to discuss the process based on important operating factors involved and to delineate some of the limitations.

Abstract: The global impact of increasing energy demands, depleting reserves of fossil fuels and increasing pollution loads on the environment due to the utilization of energy produced from fossil fuels have received considerable notice in recent years. Generation of energy from fossil fuels is generally convenient but the depleting reserves and associated global warming are major problems. One potential alternative is a shift from fossil fuel to a hydrogen (H2) based economy. H2 is considered to be a clean energy carrier with high-energy yield (142.35 kJ/g) and upon combustion it produces only water. H2 can be produced by the biological routes of bio-photolysis, photo-fermentation and dark fermentation or by a combination of these processes. Dark fermentation offers the particular advantage of using wastewater as a substrate and mixed culture as catalyst. Wastewater contains high levels of biodegradable organic material with net positive energy. One way to reduce the cost of treatment is to generate bio-energy, such as H2 gas by metabolically utilizing organic matter, at the same time accomplishing treatment. This chapter mainly focuses on the evaluation of fermentative H2-generating processes utilizing wastewater as substrate and mixed culture as biocatalyst. A particular insight was also laid on to discuss the process based on important operating factors involved and to delineate some of the limitations. Various strategies such as multiple process integration, microbial electrolysis, polyhydroxyalkanoate (PHA) production, bioaugmentation, self-immobilization and metabolic engineering were discussed in overcoming some of the limitations in the direction of process enhancement.