Thermophilic anaerobic biohydrogen production from cellulosic materials

Tizzone, Rosario
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The unabated exploitation of fossil fuel sources to provide the world with its energy demands has resulted in a dangerous increase in greenhouse gases and consequently global warming. Due to increased awareness and public concern increasing amounts of research has been devoted to identifying and developing alternative fuel sources into sustainable processes for energy production. Hydrogen is highly attractive due to its unrivalled energy density per unit mass. This present study aimed to produce hydrogen from biological sources (biohydrogen) through the process of dark fermentation. Wheat-bran was used as the fermentable carbohydrate substrate. The bioreactor system in which the experiment was conducted selected for anaerobic, thermophilic, cellulolytic hydrogen-producing bacterial consortia derived from sewage sludge. The results of this study showed variable rates of hydrogen production, ranging from 0.37 L/(L.h) to 0.78 L/(L.h). Various bioreactor parameters were monitored and it was found that hydrogen production was dependent on an optimal pH range between 5.0 and 6.0. The bioreactor proved difficult to maintain in terms of parameter conditions despite being an overall successful achievement of hydrogen production. The possibility of this bioprocessor being up-scaled into an industrially viable biofuel generator remains bleak as the energy input required to maintain optimal hydrogen production exceeds the chemical energy outputs of biohydrogen.