The aim of one of Rehap’s subtask is to optimise Biochemtex’s second generation (2G) technology to process lignocellulosic biomasses at pilot and demo scale in order to produce the lignin-rich residue and use it as starting material for the recovery of lignin and sugars for further project research.

The CTXI 2G technology is a breakthrough process able to produce fermentable sugars from lignocellulosic biomass which can be easily converted into bio-fuels and/or bio-chemicals.  The main process steps for the production of bioethanol for valorisation in this 2G process include:

  • Pre-treatment of biomass to disrupt the lignocellulosic matrix and solubilise specific sugars,
  • Hydrolysis (a reaction with water) to reduce the cellulose and hemicellulose into fermentable sugars,
  • Fermentation of sugars to ethanol,
  • The separation of solid and liquid to achieve the solid lignin, the remaining ethanol is recovered and dehydrated

During the Rehap project, CTXI evaluated the woody material, poplar, together with state-of-the-art wheat straw, in order to increase the flexibility of its conversion process to several types of lignocellulosic feedstock. None of which are in competition with food and feed.

The results confirmed that just like wheat straw, poplar presents good compositional characteristics, in terms of cellulose and hemicellulose, that allow this feedstock to be treated with 2G technology for the production of bioethanol.

Poplar was selected as a lignocellulosic material for the Rehap project improving the process of obtaining bioethanol from this material. The necessary amount of lignin co-product was produced for the subsequent R&D activities carried out by partners TECNALIA and BBEPP at lab and pilot scale, respectively.

The lignin-rich stream which will be used as feedstock for the processes in the Rehap project, is generated by the separation of solid content from the stillage recovered at the bottom of the beer stripper column in the 2G plant. This solid content is characterised by having around a 60 - 70% moisture content (MC).

In order to optimise the lignin 2G co-product for it to be used in different types of valorisations, as well as improve the power plant and water recycle processes at industrial demo scale,  CTXI carried out tests on separating the liquid and solids using polyelectrolytes and evaluating the drying process. This separation modifies lignin into a transportable solid.

The combination of separating large amounts of solids from liquids using polyelectrolytes as a separating agent as well as the drying technique, is a good solution to significantly reduce the moisture content (from 60-70% by 7-10%) to allow lignin co-product to be used successfully for combustion and/or chemical valorisation.