Pre-treatment Processes of Lignocellulosic Material for Bioethanol Conversion: Steam Explosion
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - IIa: Energy Production (T1-5a)
Keywords: Lignocelluloses, Pre-treatment, Steam Explosion, Enzymatic hydrolysis.
†Indacoechea I., Bolado S., García-Cubero M.T., Catalina I., López I.
University of Valladolid, Department of Chemical Engineering and Environmental Technology, C/Prado de la Magdalena s/n, 47005, Valladolid, Spain, Tel. +34983423166, †e-mail: iruneiv@iq.uva.es.
The presented work is part of a project researching different pre-treatment alternatives of several plant source materials that allow us to exploit the lignocellulosic material and to optimize the yield in the bioethanol process from crops suitable in Castilla y León (Spain).
Steam explosion, wet oxidation, AFEX and Ozonolysis were the processes selected as pre-treatments. The research involves the optimization of the parameters which show the higher influence in the recovery of fermentable sugars present in the selected materials. The study will be carried out with different crops appropriate to grow in Castilla y León (Spain), which amylase content permit the production of bioethanol in well established industrial processes with acceptable yields and which waste presents a high content in structural carbohydrates, in such a way that it will be possible to exploit not only the seed but also the waste.
The comparative analysis of the raw materials and products obtained in the enzymatic hydrolysis applying different operational conditions and alternatives will permit to choose, from a technical point of view, the most suitable pre-treatment to process the raw materials proposed in this project. Moreover, this information could be useful to focus the agricultural production to crop varieties that provide greater yields in the obtaining of bioethanol.
In this work it is presented the preliminary results achieved in the study of steam explosion pre-treatment. The aim of this study is to obtain both, the greatest recovery in a later enzymatic hydrolysis of fermentable sugars (hexoses and pentoses) present in the selected raw material, and a high fermentability of the recovered monosaccharide. This is because owing to the effect of inhibitors on yeast fermentation high sugar yields do not necessarily result in high ethanol yields. To evaluate these optimal conditions, a factorial design of experiments has been planned to minimize the number of experiments and to establish the effect of the parameters in the process yield. Once the optimal conditions are determined, thanks to the experimental design, a number of different raw materials are steam exploded in order to analyse the yield obtained in the enzymatic hydrolysis for the diverse materials after the treatment. The lignocellulosic materials to be pre-treated are oats, wheat, barley, rye and triticale straw, sorghum s.p. and prunning waste.
The steam explosion pre-treatment is carried out in a 5L stainless steel batch reactor (Masonite technology). Lignocellulosic material (at the desired size) is loaded at the top of the reactor and heated to the desired temperature with saturated steam, which is supplied by a boiler with a maximum operating pressure of 20 bar. When the pre-set residence time has concluded, the steam-treated biomass is released from the reactor by rapid depressurization of the vessel. After the pre-treatment, the product is washed with warm water and the residual solid is separated by filtration and analysed for acid insoluble lignin, acid-soluble lignin and carbohydrates. The liquid portion is analyzed for carbohydrates and other compounds generated during steam explosion (organic acids, furfural and HMF). The experiments arrange as a 24 factorial design which factors are temperature (180ºC, 210ºC), residence time (3 min, 8 min), particle size (0.2cm, 1cm) and the use or not of an acid catalyst (4,5% w/w SO2).
After both pre-treatments, the water-insoluble fibre is enzymically hydrolyzed in standard conditions previously established (Indacoechea I., et al 2006)1 to determine the maximum sugar yield.
1 Indacoechea I., Bolado S., García-Cubero M.T., Diez R., “Pre-treatment processes of lignocellulosic material for bioethanol conversion: ozonolysis”, 17th International Congress of Chemical and Process Engineering, Chisa, Prague 2006.
Presented Wednesday 19, 15:30 to 15:45, in session Sustainable & Clean Technologies - IIa: Energy Production (T1-5a).
