Manchester researchers uncover how to turn plant waste into valuable chemicals more efficiently

Lignin is a key structural component of plants, the largest renewable source of aromatic chemicals in nature, and is present in appreciable levels (up to 35%) in waste biomass, including that from agriculture and forestry sectors. However, its complex structure makes it difficult to break down efficiently, limiting its use in sustainable manufacturing.

In a study published in ACS Catalysis, the international research team including Dr Christopher Parlett, Xinyue Zhou, and Yutao Jiang from the Department of Chemical Engineering, has developed a highly efficient “single-atom catalyst” and, crucially, revealed how it works at the molecular level to cleave the strong chemical bonds that hold lignin together.

The catalyst uses isolated ruthenium atoms embedded in a nitrogen-doped carbon material. This design maximises catalytic performance while using very small amounts of metal, making it more efficient than conventional systems.

A clearer picture of how lignin breaks apart

A major challenge in this field has been understanding exactly which parts of the catalyst are responsible for breaking lignin’s tough chemical bonds. Without this knowledge, improving catalyst performance has remained difficult.

The researchers showed that a specific atomic configuration – known as a “Ru–N₄ site” – plays a central role. These sites activate oxygen molecules and help drive the cleavage of both carbon–oxygen and carbon–carbon bonds within lignin.

By combining experimental techniques with computational modelling, the team demonstrated how the catalyst first activates oxygen to form highly reactive species, which then attack the lignin structure and break it down into smaller molecules.

High efficiency under mild conditions

Under optimised conditions, the catalyst achieved near-complete conversion of model lignin compounds and produced high yields of valuable chemical products such as phenol.

Importantly, the system operates under relatively mild conditions and without the need for harsh chemicals, highlighting its potential for more sustainable chemical manufacturing processes.

The catalyst was also successfully applied to real lignin samples from different biomass sources, converting them into useful aromatic compounds that could serve as building blocks for fuels, plastics and other materials.

Toward sustainable chemical production

This work provides a detailed understanding of how single-atom catalysts function in biomass conversion, offering a blueprint for designing more efficient systems in the future.

“Understanding exactly how these catalysts work at the atomic level allows us to design better materials for converting renewable resources into valuable chemicals,” - Dr Christopher Parlett, Lecturer in Chemical Engineering.

By enabling the upgrading and valorisation of lignin, the research supports efforts to move away from traditional linear petroleum-derived chemicals and towards a more circular, biomass-based economy.