A team of scientists from the Institute of Science and Engineering at Kanazawa University, Japan have developed a new kind of solvent to break down plant cellulose in the bioethanol production process. The new mixtures are more environmentally friendly and easily applicable than existing forms.
While the typical bioethanol production process relies on breaking down cellulose into smaller sugar molecules, the often tough nature of this compound has proven something of an obstacle in making the fuel alternative marketable and cost-competitive. As cellulose is made up of a complex series of hydrogen bonds, it is very resistant to chemicals, and many existing methods of breaking it down involve chemicals with high toxicity. The Kanazawa team’s solution seeks to remedy this, with the new class of molecules developed – dubbed ‘zwitterions’ – dissolving cellulose efficiently and with less toxicity than typical methods.
“Our work shows that it is possible to replace many of the toxic chemicals used today with more environmentally friendly alternatives as we move towards a more renewable energy ecosystem,” senior author Kosuke Kuroda wrote.
These zwitterions have a positive and negative charge, which efficiently work on destabilising the hydrogen bonds keeping cellulose together. While they are effective cellulose solvents, they typically exist in solid form – and therefore cannot be used to break down plant biomass. The team experimented with different combinations of the zwitterionic molecules to create a liquid form of the solvent that could break down plant cellulose. The team made a total of 22 combinations of zwitterion and saccharide with a liquid state below 100°C. Of these, two were shown to successfully dissolve cellulose.
It is hoped that the research can give way to more cost-effective and safe biofuel production – using feedstocks such as switchgrass, sugarcane or other plant husks.
The study was partially funded under the Centre of Innovation (COI) program ‘Construction of next-generation infrastructure using innovative materials–Realization of a safe and secure society that can coexist with the Earth for centuries’.
Results of the team’s study were published in Carbohydrate Polymers.