Biobased chemicals and materials are expected to grow significantly and increase their market share in the coming years. Large quantities of presently underutilized lignin side-streams are available from chemical pulping processes and emerging biorefineries, offering a valuable feedstock for sustainable biomaterials.

A simple and cost-efficient alkali oxidation process for conversion of technical as well as biorefinery lignins to versatile dispersants, particularly high performance concrete superplasticizers, has been developed by VTT. This LigniOx process uses molecular oxygen as environmentally friendly and low-cost oxidizing agent and introduces acidic groups into the lignin polymer, converting it into a water-soluble polyelectrolyte. Recent mortar and concrete plasticization studies have demonstrated that LigniOx lignins have great potential to compete with lignosulfonates and even with commercial synthetic superplasticizers.

In the ongoing European research project LigniOx (2017-22), sustainable concrete plasticizers are being developed from industrial lignin side-streams from various pulp mills and biorefineries. The project aims to commercialize both the LigniOx oxidation technology itself and the LigniOx concrete plasticizers produced, enabling industrial process installations and entry of novel lignin products into the market after the project. In the coming months, the performance of the oxidation and of the end-products will be demonstrated at operation conditions. The valorization of lignin side-streams will significantly improve the cost-competitiveness and resource efficiency of lignocellulosic biorefineries, and will create low-cost, sustainable raw materials for the chemical industry and construction sector. The versatile LigniOx technology can be integrated into lignocellulosic biorefineries or be operated as a stand-alone unit by the chemical industry.

Conversion of lignin by-products into high performance materials calls for cost-effective downstream separation and purification processes. In this framework, membrane filtration is being studied by VITO for post-treatment of LigniOx liquors, targeting concentration of the oxidized lignin, improved plasticizer performance as well as chemical recovery. Generally, membrane processes can be considered a “natural” technology for separations within tomorrow’s lignocellulosic biorefineries, thanks to their low energy requirements, mild processing conditions, scalability, moderate cost to performance ratio and flexibility in equipment design. Post-treatment by ultra-/nanofiltration (UF/NF) has been shown to allow for boosting the plasticizer performance, widening its application scope, reducing transportation costs as well as recovering process chemicals. Therfore, post-treatment by UF/NF is considered critical for the techno-economic feasibility of the overall LigniOx concept. In the next few months, VITO will be carrying out a number of pilot UF/NF trials to produce LigniOx concentrates for plasticizer testing and field trials worldwide, as well as to demonstrate the techno-economic feasibility of the post-treatment under realistic conditions.

The LigniOx project is coordinated by VTT and has received funding from the Bio-Based Industries Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No 745246).