This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at the University of Illinois Urbana-Champaign have developed a fast, simple way to turn lignin, a plentiful plant-based byproduct of the papermaking industry, into potentially more valuable renewable chemicals. More than 50 million tons of kraft lignin are generated annually as a byproduct of the global pulp and paper manufacturing process.
Lignin, a complex organic polymer that gives plants and trees their structural rigidity, becomes kraft lignin when it's separated from the black liquid waste left over from the papermaking process. More than 90% of kraft lignin is incinerated onsite at paper mills to recover pulping chemicals and generate energy. In recent years, significant efforts have focused on using renewable raw natural materials, like lignin, to replace chemicals typically made from petroleum.
Finding new ways to transform and use biomass such as lignin was the overarching goal of the Illinois research team led by Joaquín Rodríguez-López, professor of chemistry at Illinois, and graduate student Supriya (Riyo) Das. Recent studies have shown great potential for kraft lignin to be used in more valuable ways, but harnessing its full potential has proved challenging through thermochemical and electrochemical methods that require catalysts and often harsh reaction conditions, resulting in low conversion rates. The new method developed by Rodríguez-López and Das uses tiny water droplets energized by sound waves to break down kraft lignin in just 20 minutes at room temperature, without added catalysts or harsh chemical conditions.
Rodríguez-López said the dark-colored powder form of kraft lignin is ultimately transformed into a redox-active molecule with a beautiful orange color in powder form. "Yes, like Illinois orange," Rodríguez-López said, explaining that the drastic color change is another indication of a reaction and transformation. In their study published in the journal Small, the team details how its microdroplet method converted about half of this complex biopolymer into a smaller molecule with potentially valuable attributes for energy and chemical applications.
Das said the process has a good conversion rate, with about 56% of the lignin converted. "So that was very interesting, very new," Das said, adding that previous studies using other methods to depolymerize lignin have not reported such a high yield of a selected product. Das said it has been exciting to discover this unique molecule and name it.
The Sonicated Emulsive Microdroplet, SEM, compound was discovered at Illinois, ILL, so the team named it SEMILL-A. "I think that we've tapped into a unique process to deconstruct complex biomass. And that's what makes it so very rewarding," Rodríguez-López said.
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