Microbial hydrogen production by bioconversion of crude glycerol: A review

Hydrogen is a clean source of energy with no harmful byproducts produced during its combustion. Bioconversion of different organic waste materials to hydrogen is a sustainable technology for hydrogen production and it has been investigated by several researchers. Crude glycerol generated during biodiesel manufacturing process can also be used as a feedstock for hydrogen production using microbial processes. The possibility of using crude glycerol as a feedstock for biohydrogen production has been reviewed in this article. A review of recent global biodiesel and crude glycerol production and their future market potential has also been carried out. Similarly, different technical constraints of crude glycerol bioconversion have been elaborately discussed and some strategies for improved hydrogen yield have also been proposed. It has been underlined that use of crude glycerol from biodiesel processing plants for hydrogen production has many advantages over the use of other organic wastes as substrate. Most importantly, it will give direct economic benefit to biodiesel manufacturing industries, which in turn will help in increasing biofuel production and it will partially replace harmful fossil fuels with biofuels. However, different impurities present in crude glycerol are known to inhibit microbial growth. Hence, suitable pretreatment of crude glycerol is recommended for maximum hydrogen yield. Similarly, by using suitable bioreactor system and adopting continuous mode of operation, further investigation of hydrogen production using crude glycerol as a substrate should be undertaken. Furthermore, isolation of more productive strains as well as development of engineered microorganism with enhanced hydrogen production potential is recommended. Strategies for application of co-culture of suitable microorganisms as inoculum for crude glycerol bioconversion and improved hydrogen production have also been proposed.