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Cellulosic alcohol technology: commitment & excellence exemplified

A team of 20 PhD students from multiple disciplines led by Dr Arvind Lali and nine years of relentless toil against the tide that is, what it took to develop India’s first home grown technology to convert biomass to ethanol with speed and efficiency. To top it, conversion is four times faster than other technologies currently available in the international market.
With other technologies, the time taken is 4 to 7 days, the one developed by the DBT-ICT Centre for Energy Bio-Sciences team at Institute of Chemical Technology; Mumbai converts it in 18-20 hours and produces about 300 litres of ethanol per ton of biomass.

The process involves three steps—chemical fractionation, enzymatic hydrolysis and fermentation. In the first step, lignocelluloses are broken down to cellulose, lignin and C5 sugars by means of acid fractionation. A mixture of cellulose and lignin through alkali fractionation then separates to cellulose and lignin streams.

Cellulose through enzymatic hydrolysis breaks down to C6 sugars.
The non-sugar organic components can be simply converted into energy by direct burning while inorganic silica can be recovered and sold as by-product. The burning provides steam, as energy, required for ethanol distillation, while both C6 and C5 sugars through fermentation yield the desired ethanol.

While fermentation of C6 sugars is relatively simple, C5 sugars (xylose) sugars need special yeast strains. In the new technology, innovative fermentation has led to innovative bioconversions of both C6 and C5 sugars to ethanol. High-density continuous fermentation with controlled concentrations of clean sugars gives high-speed efficient fermentations with high yields.

At present, the cellulose degrading enzymes used in the process are imported, and the challenge is to produce these enzyme production technologies in India. The DBT-ICT Centre is working alongside several other Indian institutes to meet this objective.

The journey to the indigenous cellulosic or 2G-ethanol technology may have started on Dr Lali’s return from Sweden with expertise in the art and science of bio-separations and enzyme technologies. Soon he and his team at ICT were well known for providing cost effective solutions to the biotech industry on downstream processing and enzyme technology.

His career took a new turn when in 2007 Department of Biotechnology was looking for a team which could set up India’s first Centre for Energy Biosciences. He took up the challenge and got a team together consisting of scientists and students from chemistry, enzyme technology and engineering, bioinformatics, fermentation technology and chemical engineering.

The team was geared to operate in non-traditional ways in many senses. They dreamt of a technology that could convert biomass to ethanol as early as possible. In the process, they decided not to take the beaten-track. They went ahead with new ideas that struck them—a hunter gatherer’s rather than a farmer’s approach.

Today, the technology stands out as potentially one of the best in the world for efficient and controlled fractionation of biomass to its components cellulose, hemi cellulose and lignin; rapid enzyme hydrolysis of cellulose with enzyme recycle and reuse using a patented technology; and high cell density continuous fermentation of both C6 and C5 sugars using our own developed strains to provide rapid and efficient fermentation.

Biomass structure is complex and varies with feedstock and its age. The challenge is to treat all types through a single technology and yet obtain intermediates of a consistent quality. Specific enzymes break cellulose structure in complex ways. Understanding their action is key to their effective use at a large scale.

A two-step controlled chemical deconstruction of any biomass gives consistent high quality of cellulose. Xylose and lignin is recovered for processing. Carefully designed slurry flows permit rapid reactions with high efficiencies. This followed by a continuous and rapid enzyme hydrolysis yields clean sugar in high yields for efficient fermentation.

Important features of the DBT-ICT 2nd generation ethanol technology are low capital cost compact technology; continuous processing from size reduction to fermentation; recycle and reuse of chemicals, enzymes and water; high recoveries of sugars with almost zero toxics formation. The last feature helps effective production of sugars that can also be diverted to other products.

The DBT-ICT 2nd Generation-Ethanol Technology was translated successfully to a demonstration scale plant capable of processing 10 tons biomass/day. This plant has been erected by India Glycols Ltd. (IGL) with financial assistance from BIRAC. The future biomass bio-refinery at IGL aims to produce lignin &sugar from biomass waste, and convert these to alcohol for production of ‘green’ monoethylene glycol, bio-CNG, and materials that are equivalent to PET, in addition to chemical solvents like furfural and ethyl acetate and even foods like glucose and fructose.