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Energy balance of hydrogen production from wastes of biodiesel production

ABSTRACT Biodiesel production across the globe has resulted in a proportional increase of crude glycerol (CG) as waste by-product. Utilization of CG will increase the economic viability of the biodiesel industry. This study compared the energy balance for CG utilization during dark fermentation for hydrogen production with glycerol purification for glycerol. The energy balance for each of the materials used during inoculum, media preparation steps and electricity consumed across both the methods was calculated. The total energy input for glycerol purification (872.39 MJ) was 2.5-fold higher in comparison to maximum total energy input of vegetable feedstock derived CG (344.25 MJ). The market value of pure glycerol is decreasing in comparison to increasing market value of hydrogen as fuel. For efficient utilization of CG, bioconversion to hydrogen production by dark fermentation can be considered an energy efficient and sustainable fuel generation option. The net energy (MJ) for different feedstocks (vegetable source 158.90, multi-feedstock 113.23 and animal waste 83.14) during hydrogen production varied with glycerol content. Performing dark fermentation at ambient conditions and utilization of electricity generated from biogas capture will surely reduce the total energy input. By doing so, the net energy for different feedstocks will have a positive value.