Petrochemistry and Chemical Engineering

The high demand for clean energy source has in recent past created a great interest in biofuels. Among the biofuels that are highly investigated include; bioethanol, biohydrogen, biodiesel and biomethane. Biohydrogen has a special advantage in that no greenhouse gas is emitted during its combustion. It can be produced from organic wastewater but the yields remain low. The survey of the published data shows that the most promising production method is the dark hydrogen fermentation. Some of the strategies for improving biohydrogen production from organic effluents include: bioreactor modifications, microbial culture immobilization, culture selection and enrichments, substrate choice and the optimization of process conditions (temperature, pH, organic loading rates (OLR) and hydraulic retention time (HRT). The recommended biohydrogen production method is a sequential combination of biohydrogen and biomethanation production phases which has the potential for producing the highest bioenergy recovery from organic wastewater. The biorefinery production concept where biohydrogen is produced together with other biofuels and bio products is the ultimate cost effective production process. Due to very short optimal HRT for biohydrogen production, the choice of reactor configuration that helps retain biomass like Upward Sludge Bed Reactor (UASB) and immobilization of biomass should be considered to improve the productivity. The use of appropriate biohydrogen specialists and biomass recirculation will also improve the process effectiveness.