Within the Institute of Chemical Engineering and Environmental Technology (CEET), the Working Group Biorefinery is at the forefront of the development of innovative processes for the isolation of valuables from biobased process streams, down cycle raw material utilization along the whole production chain is targeted.

Our research is driven by the need of the transfer from a fossil based to a biobased economy. The bioeconomy builds upon the three pillars bio-fuels, bio-energy and bio-products. The biorefinery, as the complement to a conventional refinery shall deliver different products by cascade raw material utilization. The biobased industry will play an essential role during this transformation process, where the pulp and paper industry may serve as backbone, because they have large knowledge dealing with biobased raw material all year.

Our research approach is to generate added value from existing process streams, where we start from the basics like measurement of phase equilibria, followed by the process design accompanied by hydrodynamic simulations. Process integration on site of the developed processes is one main point during development. At present we focus on the isolation of technical lignins and on the isolation of carboxylic acids from existing process streams.

• Lignin isolation from pulping processes

Besides cellulose lignin is the second most abundant bio-polymer. Lignin is dissolved during wood digestion and is then used in the chemical recovery cycle as fuel in the recovery boiler. Depending on the cooking process two different lignins are achieved, on the one side lignosulfonates and on the other side Kraft lignin. The two lignins differ in their behavior, while lignosulfonates are soluble over the whole pH range, Kraft lignin is soluble at pH higher then 10. Hence, different approaches for the isolation thereof need to be developed.

Kraft lignin can be isolated by precipitation, we address the utilization of plant derived CO₂ as well as the pre-treatment of lignin in terms of filtration behavior.

• Isolation of carboxylic acids

Carboxylic acids are bulk chemicals and are at present products from oil refining or for example lactic acid is produced by fermentation. However, carboxylic acids are present in industrial effluents from the biobased industry, but are not isolated yet. Isolation thereof is challenging as the concentration of carboxylic acids is low, in general a mixture of carboxylic acids is present and the process streams very often have cell debris in or pH value is rather high.

During Kraft pulping not only lignin, but also carboxylic acids are dissolved into black liquor and also in other effluents carboxylic acids can be found. A fractionated isolation of the different carboxylic acids is tested technically and economically. Further process streams are e.g. silage sludge, where mainly lactic acid is present.

• K-Project Flippr² - Future Lignin and Pulp Processing Research PROCESS INTEGRATION focusses its efforts on integrated solutions to efficiently manufacture value-added products from wood.
   
• FFG bridge project KrAcid - Process design for the isolation of carboxylic acids from pulping effluents and Integration of the isolation and purification process in the overall pulping process
   
• IEA IETS Annex 17 - Membrane separation processes combine the advantage of material usage of the components by partly selective separation mechanisms with energy efficiency measures.
   
• ERA-NET Bioenergy Up-Whey - Upstream processing of lactose whey for bulk chemicals and energy production. Basics for the isolation of lactic acid from whey production and transformation of basics into a membrane reactor
   
• IEA IETS Annex 17 - Membrane processes in biorefineries, present and potential applications.

• LignoFracStore: Fractionation and conversion of lignin for sustainable eneryg storage