Valorisation of hydrolysis lignin rest from bioethanol pilot plant: Process development and upscaling

The aim of this work has been to find a scalable process to purify lignin and separate the cellulose-rich fraction from a poplar wood hydrolysis rest produced at a bioethanol pilot-plant. At initial laboratory optimization, a mild extraction of lignin was performed with 1 M NaOH at 90 °C to dissolve the lignin, that was further precipitated with sulfuric acid and this formed an easily filtrable powder. The main sub-product was a solid residue enriched in cellulose, which was successfully saccharified and tested for its fermentability. Further upscaling of the method was done at Bio Based Europe Pilot Plant (BBEPP) in Belgium. In a first run 14.2 kg of purified poplar lignin was obtained and in a second run 128.6 kg was obtained. The wet fiber residue was processed by washing and enzymatic hydrolysis to obtain, 26.7 kg of concentrated sugar solution with 509.4 g/L of glucose.