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Researchers at Kanazawa University, Japan, claim to have developed a new type of solvent for the production of next-generation, non-food biofuel.

According to a research paper, entitled 'Design of wall-destructive but membrane-compatible solvents', a novel carboxylate-type liquid zwitterion was developed as a solvent of biomass, which could be used to dissolve cellulose with very low toxicity to microorganisms.

Background

As first-generation biofuel is produced from foodstuffs such maize, it raises concerns about a possible future food shortage. For this reason, the idea behind producing second-generation biofuel is to use non-food biomass such as weeds, waste paper and paper cups.

However, the solvents used for the production of second-generation biofuel up until now have been highly toxic to microorganisms, so in order to remove the toxic solvents, complex processes are used, such as washing with water, separation by centrifugation, and compression, which in turn use up a lot of energy and are negative for the environment.

Project

The researchers say they succeeded in reducing the toxicity to microorganisms by developing a novel solvent, a carboxylate-type liquid zwitterion, for dissolving biomass cellulose.

EC50, the concentration of a substance that reduces the growth of Escherichia coli to 50 percent, was found to be 158 g/L for the newly developed carboxylate-type liquid zwitterion, whereas the EC50 of ionic liquid - one of the conventional solvents of cellulose - was 9 g/L.

This, the researchers say, indicates that the novel carboxylate-type liquid zwitterion shows 17-fold lower toxicity than the ionic liquid.

With Escherichia coli that can produce ethanol, fermentation ability was examined and revealed to be almost maximal in 0.5 mol/L carboxylate-type liquid zwitterion with a final ethanol concentration of 21 g/L, while the same experiment with the ionic liquid produced only 1 g/L ethanol. Thus, fermentation in the presence of the carboxylate-type liquid zwitterion produced 21 times more ethanol than that using ionic liquid.

In another experiment, bagasse was used as a starting plant biomass for ethanol production without washing/separation processes. Fermentation in the presence of the carboxylate-type liquid zwitterion produced 1.4 g/L ethanol, while no ethanol was obtained with the ionic liquid due to its high toxicity.

With these experimental results, the researchers say that using the carboxylate-type liquid zwitterion, plant biomass could be converted into ethanol in a single reaction pot without washing/separation processes.

"This should be a big step forward in the production/utilization of second-generation biofuel ethanol through reducing large amounts of energy input," the researchers said.

Third-generation biofuel

The researchers also claim that further development of their study would significantly contribute to the potential production of third-generation biofuel ethanol - a kind of oil that could be made from algae.

In order to obtain a third-generation biofuel from algal species, polysaccharides like cellulose, which are main components of cell walls, need to be dissolved.

Energy efficiency would increase significantly if dissolved polysaccharides could be converted into ethanol, the researchers say.

Last week's report

On Friday, Bunker Index reported that Lloyd's Register and London's University Maritime Advisory Services (UMAS) had released a report that ranked biofuel as the best zero-emission solution currently available to power ships.

The report stressed that advanced, non-food-derived, sustainability-certified biofuel will be required if the amount needed to fuel the shipping industry is not to clash with the basic need for food with a growing global population.