I am a PhD student at the Institute of Chemical, Environmental and Biosciences Engineering at TU Wien (Austria). My research focusses on the extraction of lignin from wheat straw by organosolv pre-treatment. Austria produces large quantities of wheat straw as an agricultural by-product, but this feedstock is currently not fully utilized, which makes it a suitable feed for lignocellulosic biorefineries. The ethanol organosolv pre-treatment has the advantage of producing sulphur free lignin of high quality (compared to e.g. the Kraft or the sulphite process), which can be potentially used for value-added products and thus improve the economic aspects of a lignocellulosic biorefinery. The extracted straw on the other hand has potential use as a fibre or as feedstock for sugar production via enzymatic hydrolysis for further valorisation. The addition of an acidic catalyst has potential impacts on key aspects of the organosolv pre-treatment, like the delignification, the pulp yield and the enzymatic digestibility. However, as mineral acids may induce important problems like corrosion and may also impact the quality of the lignin obtained, alternative catalysts, such as organic acids, can be interesting alternatives. Nevertheless, there is still much to learn about the behaviour of those catalysts and their impact in the process and a lot of room for optimization to meet all requirements.
I visited LNEG for two weeks to investigate the influence of acetic acid as a catalyst in the ethanol organosolv pre-treatment, learn new methods for the characterization of the pre-treated biomass, and to get to know the research facility and the people working there. My work at LNEG was split into two parts: The first week consisted of the experimental work, where I carried out eight organosolv extractions with four varying concentrations of acetic acid. All extractions were carried out in a 600 mL stainless steel stirred reactor for one hour with 30 g of dry straw and 330 g solvent at a maximum temperature of 180 °C, which was reached 30 minutes after the start of the treatment. After each extraction, the extract and the solid fraction were separated with a hydraulic press, and the solids were washed twice to remove all soluble residues. In the second week, I did the enzymatic hydrolysis of the extracted straw as well as the analytical work, consisting of the analysis of the extracted straw on lignin, carbohydrate and ash content and determination of the concentration of carbohydrates, degradation products (such as HMF and Furfural) and perceptible lignin in the extract. The results will show how the addition of acetic acid influences the pulp yield, the delignification and the enzymatic digestibility of the straw, which will help to better understand the process and further optimize it.
I would like to thank everyone at LNEG for their support in the organisational and practical work, especially Dr. Florbela Carvalheiro, Dr. Luis Duarte, Dr. Tiago Lopes and Vanmira Van-Dunem.
I benefitted greatly from my BRISK2 visit at LNEG by practicing new methods, comparing the working conditions at different laboratories, exchanging knowledge and thoughts with researchers of the same subject and gathering valuable information on the influence of acetic acid on organosolv extraction. Additionally, I had the opportunity to go to Lisbon for the first time and visit this amazing city in my spare time.
Figure
Extractor during extraction
Johannes taking notes of pressure and temperature during the pre-treatment
Sample preparation after liquor hydrolysis
Dried precipitates (Left to right: extraction 1 – 8)
