REASONED PRODUCTION OF LIGNINES AND HÉMICELLULOSES BY COUPLING OF ASSISTED MECHANICAL PROCESSES – LigNoV

This project, which include two laboratories (UMR IATE and LCA) and a company specialized in purification process engineering (NOVASEP), aims to develop a process for lignocellulosic biomass fractionation for the common valorization of the three main compounds, cellulose, lignin and hemicelluloses. Two plant residues were retained as models, sunflower oilcake and cane bagasse. Bagasse was retained because it mainly contains the three molecules and oilcake because it will induce extra difficulty, as the protein separation.
The studied fractionation process is based on coupling dry grinding and twin-screw extrusion, for the production of three purified fractions, containing cellulose, hemicelluloses and lignin. In a first step, grinding will aim at separating the plant tissues according to their composition, and then producing enriched fractions in cellulose, hemicellulose and lignin. The work will try to minimize the grinding energetic consumption while allowing fine dissociation of the tissues. Then, the produced fine particles will be separated by an electrostatic procedure, developed at IATE UMR. This process, that segregate the particles according to their surface properties and their composition, aims to produce enriched fractions in lignin-hemicelluloses, cellulose and proteins without the introduction of a solvent or a catalyst. This step will also aim to minimize the number of further purification stage.
The extraction of the target molecules will be achieved on the produced solid fractions will be managed in the most favorable conditions for the recovery (acid, alkaline, enzymatic) and will lead to the production of liquid extracts. In order to minimize the amount of introduced chemical, the chemical action will be coupled to the mechanical and thermal action by using a twin-screw extrusion. The extraction results obtained on the IATE solid fractions (yield, purity, energy, waste) will be compared to those obtained by direct extraction on the raw material by twin-screw extrusion and conventional processes like organosolv or alkaline in autoclave.
The efficiency of the liquid extract production phase (dry grinding couple to extrusion) will be compared to the efficiency of reference technology such as organosolv or sodium hydroxide extraction (in stirred reactor or autoclave). Nevertheless, the quality of the extracts will be different and will lead to different purification chains.
Thus, the project will also aim to study the purification of enriched liquid extracts, in hemicelluloses and lignin. The considered purification pathways are membrane, including electro-dialysis, and resin technologies associated to classic liquid/solid separation processes (filtration and centrifugation). During this phase, the conditions will be optimized also for the reference processes. The aim is to define the purification pathway of the extract coming from the different technologies that could be industrially developed, and then be able to compare them at the same scale. This study will also include the extract characterization, in order to define if other valuable molecules can be refined, such as tannins or monomeric phenolic compounds.
The value of the studied process is to reduce the quantity of introduced solvent that allow for the development of a sustainable process according to the green chemistry principles. Furthermore, the process optimization will take into account its environmental impact by coupling the life cycle analysis methodology with the chemical engineering models. All the experimental trial will get the date required for the life cycle analysis. This phase will conclude by the definition of the optimal conditions.
The most efficient process for each substrate will be validated a larger scale in order to get the required date for further industrial scale-up.