סמינר חוגי Turning Plant Wastes to Bioethanol using Ozone Pretreatment

Title: Turning Plant Wastes to Bioethanol using Ozone Pretreatment

Abstract: Lignocellulosic waste (here municipal trimming) is a promising sustainable feedstock for ethanol production, but requires costly and polluting pretreatment, often resulting in toxic byproducts. Ozonation is a nonpolluting, effective pretreatment method, but is commercially unused due to the high energy required for the production of the high ozone doses assumed needed. My results demonstrated low-dose ozonation (15 min ozonation, accumulated TOD = 318 mgO3 L-1) of water-submerged waste could result in effective high enzymatic saccharification efficiency (cellulose fraction converted to glucose) compared to non-ozonized sample although only fraction (25 %) of the lignin was degraded. These results suggest ozonation could offer an effective and feasible pretreatment method, showing that there is no need for delignification (as opposed to the common hypothesis) for high sugar release. In addition, the ozonation process was accompanied by changes in absorbance, mainly at 280 nm, making it a useful tool for process monitoring. Net calculated energy balance was positive for all ozonation regimes, with increased process efficiency at lower ozone doses. Furthermore, ozonation can be generated on-site and on demand, enabling decentralized pretreatment operated near the feed source thus overcoming transportation costs. Moreover, common pretreatment methods in bioethanol production involving heat and/or diluted sulfuric acid degrade the carbohydrates fraction and causing the formation of four aldehydes: formic acid, levulinic acid, furfural and HMF (5-hydroxymethylfurfural). These by-products are known to have an inhibitory effect on the fermenting yeasts and consequently reduce ethanol production efficiency. This research is investigating the effect of ozonation upon these four substances and the consequence effect upon yeasts inhibition as a suggested additional post pretreatment procedure. Results of ozonation effect on the inhibitors showed that 15 min ozonation was able to remove over 90 % of 50 mM furfural, 50 mM formic acid and 25 mM HMF inhibitory effect and almost 100 % treated 100 mM levulinic acid. These results are suggesting the applicability of ozonation as an effective method for inhibitors removal in bioethanol production process.

Speaker: Yan Rosen is a PhD student in the Porter School of Environmental and Earth Sciences, under the supervision of Prof. Hadas Mamane and Prof. Yoram Gerchman.