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IIT-KGP taps microwave radiation to create clean energy from Sunn Hemp


IANS Kharagpur
Researchers at the Indian Institute of Technology-Kharagpur (IIT-KGP) have tapped microwave radiation to create clean energy from nitrogen-rich non-food Sunn Hemp plants, the premier institute said on Monday.
While the significant industry potential of the invention has led the scientists to file for a patent, their findings have also appeared in the globally renowned journal Bioresource Technology, published by Elsevier.
With the ongoing initiatives to control pollution, there is now an urgency to replace the use of fossil fuels like petrol and diesel which directly cause pollution, global warming and climate change.
Researchers have found there is potential for making available biofuels derived from high-energy plant sources, such as Sunn Hemp, on a large scale as a replacement of fossil fuel which can find significant use in the transportation sector.
The main obstacle to its large-scale deployment as a future fuel is its highly crystalline structure and long polymer chains, which make the fibre inaccessible to enzymatic and chemical treatments, an IIT official said.
Researchers from IIT-KGP's P.K. Sinha Centre for Bioenergy have overcome the obstacle through the use of microwave radiation. The team from the Bioenergy Lab at the Department of Chemical Engineering has successfully converted non-edible lignocellulosic fibres of Sunn Hemp to biofuel precursors.
The entire conversion, which otherwise takes about 8-10 hours, was completed in only 46 minutes using the microwave reactors in the lab.
"One kg of Sunn hemp fibres containing 756 grams of cellulose, produces 595 grams of glucose at 160 degrees Celsius, and 203 grams of hydroxymethylfurfural (HMF) at 180 degrees Celsius in 46 minutes. The glucose is separated and fermented using yeasts to produce 230 gram of ethanol-based biofuel which is often used in automobiles as a biofuel additive for gasoline. The platform chemical HMF can also be hydrogenated to furanic biofuels such as dimethylfuran which can be used as a replacement for diesel," explained researcher Souvik Kumar Paul.
Sunn Hemp is widely grown in the subtropics of Bangladesh, Brazil, India, Pakistan, Russia, Sri Lanka, the US, and Uganda. It is grown in almost all states of India, especially Bihar, Odisha, Rajasthan, Uttar Pradesh and West Bengal.
The large-scale availability of Sunn Hemp in India along with its fast rate of growth and high cellulose (75.6 per cent) and high energy contents are the key elements of listing it as a top choice for the biofuel industry.
"Sunn hemp fibre has the unique potential of being converted to transportation biofuels rather than being merely used as bast fibre for weaving mats, etc. Our research will give its chemical composition the necessary stability for conversion and deployment as liquid biofuels, which can be used by the transportation industry in a large scale," said Professor Saikat Chakraborty, lead researcher and faculty at the Department of Chemical Engineering and P.K. Sinha Centre for Bioenergy.
The chemical reactions were performed by the IIT-KGP scientists in a large microwave digestion system that houses 16 high-pressure tubular reactors.
By combining the dried Sunn Hemp fibres with chemicals such as ionic liquid and metal catalysts, and water at high temperatures, they created large molecular structures in the microwave reactors.
The supramolecular complex being polar in nature rotates under the microwave's alternating polarity and rapidly dissipates the electromagnetic energy through molecular collisions across the reactors.
These dipole rotations and intermolecular collisions help rapidly break the polymeric bonds in the Sunn Hemp fibres and convert them to biofuel precursors in only 46 minutes.
"Biofuel production cost is minimised by recovering and recycling the ionic liquid. This conversion process can be used not just for Sunn Hemp but also for a large spectrum of non-food lignocelluloses (plant dry biomass) abundantly available in the country, which is usually difficult and slow to hydrolyse using conventional processes," Chakraborty added.

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First Published: Feb 26 2018 | 4:48 PM IST

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