Value added products from sawdust pine in a biorefinery platform

CLAUSER, N.; GUTIÉRREZ, S.; AREA M. C.; FELISSIA, F. E.; VALLEJOS M.E.

Montevideo

Workshop; I&S WORKSHOP. Insights and strategies towards a bio-based economy; 2016

Universidad de la República; I+D+i . Technological Laboratory of Uruguay (LATU); Instituto Nacional de Investigación Agropecuaria (INIA). Uruguay - VTT - Technical Research Centre of Finland; Faculty of Chemistry and Engineering. Åbo Akademi University. F

The main activity of the production of wood pulp and products in Argentina is concentered in Misiones. Pine is one of the most important raw materials for these industries. Pine sawdust is an important lignocellulosic waste of the primary industrialization of wood. The valorization of pine sawdust using the biorefinery platform could add new values chains into Argentina?s forest industry and can serve as a model for the industry of other countries in the region. The most typical large-scale biorefinery scenario is based on the extraction of sugars from biomass to produce cellulosic ethanol, steam, and electricity. Depending on the available raw material, there are numerous products that could be obtained from a small-scale biorefinery platform. Some advantages of small-scale biorefineries (10 to 50 employees) are lower capital and logistics costs, and lower inversion risk than those of large-scale ones, in addition to the possibility of labor occupation in rural areas. The processing model of this work includes a sequential alkaline-acid fractionation of pine sawdust to remove extractives (alkaline treatment) and to solubilize the hemicelluloses (acid steam explosion). Based on experimental data, the considered alkaline treatment is performed at 90 °C with 5% NaOH, liquid-solid ratio of 5.5:1 and during 60 min. For steam explosion, a model to determine the composition of hemicellulosic sugars (glucose, mannose, galactose, and xylose) of the liquid fraction and the solid yield was developed as a function of time, temperature, and acid concentration. Using the GAMS Software (CONOPT solver) these parameters were determined to maximize solubilized hexoses. The scenario proposes the production of levulinic acid and other byproducts (furfural and formic acid) from hexoses, and pellets from the residual solid (150°C, 2.5%H2SO4 during 250 minutes). Levulinic acid is obtained by acid catalysis of the hexoses in the liquid fraction from steam explosion, recovering levulinic acid and byproducts. For pellet production, the process involves drying, grinding to reduce the particle size, pelletizing, cooling to allow solidifying, strengthening of the pellets to bring strength and durability to granules, and finally screening through a vibrating sieve to remove fine material and to ensure a clean fuel source. For these subsequent conversion processes, updated bibliography conditions were adopted in order to determine the total production volumes from each fraction and to estimate the mass and energy balances. Alkaline treatment yield is 92%, removing about 90% of extractives. The estimated conditions to maximize the solubilized hexoses in this treatment are 200 °C, 3% H2SO4, and 10 minutes. Under these conditions, 134 kg of hexoses (49% glucose, 40% mannose, 11% galactose) and 32 kg of xylose are solubilized. The energy consumption of the combinated alkaline and steam explosion treatments are 629kW and 465.7 kW for tone of pine sawdust. In these operating conditions, the amounts of levulinic acid and pellets obtained are 32 kg and 576 per ton of dry pine sawdust. The market prices of levulinic acid and pellets are 5000-8000 USD and 120-156 USD per ton of products, respectively.