Dark Fermentative Hydrogen Production

Dark fermentation is the fermentative conversion of organic substrate to biohydrogen, it is a complex process manifested by a diverse group of bacteria by a series of biochemical reactions involving three steps similar to anaerobic conversion. Dark fermentation differs from photofermentation because it proceeds without the presence of light. 

Carbohydrates are the preferred organic carbon somce for hydrogen-producing fermentations. Glucose in the biomass yielded 2 and 4 mol per mol glucose 

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Hawkes, F.R., Hussy, I., Kyazze, G., Dinsdale, R. and Hawkes, D.L. (2007) Continuous dark fermentative hydrogen production by mesophilic microflora Principles and progress. Int. J. Hydrogen Energy 32, 172-184. 

In conclusion, the rates and efficiencies of hydrogen production by systems directly using photosynthesis fall short of even plausible economic feasibility. Since organic substrates are the ultimate source of hydrogen in photofermentations or indirect biophotolysis processes, it can be argued that it should be simpler and more efficient to extract the hydrogen from substrates using a dark fermentation process, an approach which is discussed next. 

Bioprocesses for hydrogen production are in an early stage of development. Processes are usually split in those requiring incident sunlight (bio-photolysis and photo-fermentation) and those that can be carried out in the absence of light (dark fermentations). 

HYDROGEN PRODUCTION FROM FOOD PROCESSING WASTEWATER AND SEWAGE SLUDGE BY ANAEROBIC DARK FERMENTATION COMBINED WITH PHOTO-FERMENTATION... 

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