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Scripting a roadmap to produce biohydrogen

Read time: 4 mins
25 Apr 2018
Infographic : Purabi Deshpande / Research Matters

In the past century, fossil fuels like petrol and diesel have powered our vehicles, machines and in fact, our world! But the era of these fuels is coming to an end; all our petroleum reserves are soon ending, and the increasing pollution due to these fuels is making the world sick. Now, our hope lies in biofuels—fuels produced by organic wastes that are renewable and eco-friendly, unlike fossil fuels. In a step that can make biofuels a reality, researchers at the India Institute of Technology Kharagpur are scripting a new roadmap for India's biofuel demands by exploring efficient ways to produce biohydrogen.

"Biofuels can be harnessed easily. It can also be used in existing combustion engines after blending with petroleum diesel to various degrees. No separate transportation infrastructures would be required for such fuels", says Prof. Debabrata Das, in his article in the journal INAE Letters. He also leads the Bioprocess Engineering Laboratory at IIT Kharagpur where researchers are developing expertise in the field of biohydrogen production.

Biohydrogen is the hydrogen produced from organic wastes. As a fuel, hydrogen has the highest energy density, yielding 143 kJ per gram. Compare that with diesel that yields about 48kJ per gram! It is also a clean fuel, emitting no poisonous gases when burnt, and is eco-friendly too. While natural hydrogen is abundant, it is easy to use the hydrogen produced by fermentation of organic wastes as fuel.

In their research, spanning over many years, the researchers have investigated different kinds of chemical processes, bacteria and the organic medium needed to produce the most amount of hydrogen. “The main objective of the research work is to improve the biohydrogen production process with the primary emphasis being to increase yields of hydrogen from the existing processes using organic wastes”, they say.

The centre-piece in the production of biohydrogen are the microorganisms that break up the carbohydrates in the organic wastes and produce hydrogen as a byproduct. In this study, the researchers investigated a wide range of potential hydrogen producing microorganisms, including those that tolerate a very high temperature (thermophiles) and those that grow best in moderate temperatures (mesophiles). They found that Klebsiella pneumoniae, a lactose producing bacteria, produces hydrogen at a higher rate than other mesophilic organisms. It works best at an optimum temperature of 36 °C and a pH of 6.5.

The researchers also studied various organic media which these microorganisms ferment to produce hydrogen. Algal biomass (organic waste rich in algae), deoiled cakes of groundnut, coconut and mustard, starchy wastewater, plant dry matter, cane molasses and cheese whey were some of the medium studied. Using mathematical models, they designed bioreactors, where the fermentation takes place. They studied the composition of the biomass and the breakdown products and measured the amount of hydrogen obtained from each medium.

The researchers have also investigated the potential of acidogenic bacteria—bacteria that produce fatty acids and acetic acid as byproducts—in the fermentation process without oxygen. They have also employed an innovative approach of ‘dark’ fermentation—fermentation in the absence of light—followed by the removal of carbon dioxide to harness only the hydrogen. This method yields the maximum production of hydrogen.

Funded by the Ministry of New and Renewable Energy (MNRE—India), Defence Research and Development Organisation (DRDO—India), and the Department of Biotechnology the researchers have developed customised bioreactors to produce hydrogen continuously for use in fuel cells and other applications. They have built a prototype with a 20-litre bioreactor that uses agricultural residues, and the live demonstration of the same can be seen here.

The researchers are now vying for large-scale hydrogen production for commercial applications. “Our endeavour with large-scale biohydrogen production has motivated us to commercialise biohydrogen production process for decentralised energy solution”, they say. So far, the bioreactor at the institute has been able to produce 76.2m3 of hydrogen using 10,000 litres of cane molasses supplemented with groundnut de-oiled cake at 34–37 °C.

With natural sources of energy like the fossil fuels unable to quench the world’s energy demands, biohydrogen holds hopes of clean, green and cheap energy for the future. “Hydrogen production using organic wastes/residues could become a promising way for economical and sustainable clean energy generation which also leads to waste management”, the researchers say.