Methods for enhancing bio-hydrogen production from biological process: A review

Hydrogen (H-2) is considered a clean source of energy and an ideal substitute for fossil fuel owing to its high energy content (122 kJ/g), recyclability and non-polluting nature. The conventional physicochemical methods for hydrogen production are costly owing to high energy input requirements. Hydrogen production by means of biological processes is considered the most environmental friendly and relatively easy to operate, with successful operation under ambient conditions and promising techniques, and having significant advantages compared with conventional chemical processes. The major bottlenecks in biological processes are the low hydrogen yield and production rates at a large scale. The target is improvement of the biological method for hydrogen production and devising path even better in comparison to the conventional methods. The present review article aims to highlight various techniques such as pretreatment, cell immobilization, sequential fermentation, combined fermentation that have been used in biological processes for enhancing hydrogen production. Future developments on these techniques are also outlined. (C) 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.