DETERMINATION OF THE EFFECTS OF AQUEOUS AMMONIA PRETREATMENT ON THE STRUCTURE OF SOLID CAKE VIA STATISTICAL ANALYSES AND CHARACTERIZATION METHODS

Abstract

Pretreatment of biomass prior to use for ethanol production is considered as an important step in increasing efficiency ofprocess. Among various procedures, treatment with NH3 is an effective and facile method for delignification of biomass withhigh lignin content. Solid cake, utilized in this study is a lignocellulosic biomass with rich organic content. NH3 pretreatmentwas conducted in the course of study to determine its effect on lignin degradation and decreasing cellulose crystallinity. Thistreatment procedure is a one-step process unlike consecutive dilute acid hydrolysis and alkaline treatment with NaOH whichwere currently being used in sugar production. Temperature used in experiments were varied between 30-70ºC. These valueswere much lower than conventional dilute acid hydrolysis which enabled the treatment to be energy efficient.Alternative use of solid cake as a biomass source in ethanol production would be beneficial in reducing the costs of olive oilproduction. Efficient use of this biomass depends on degradation of its high lignin content and the decrease in its cellulosecrystallinity. Hence determination of optimum conditions utilized in NH3 pretreatment is crucial to achieve economicproduction ethanol. The pathway in NH3 treatment of olive oil cake was presented with this study. Solid cake was treated atvarying times, NH3 amounts and temperatures and the changes in biomass structure were determined in terms of lignin contentand cellulose crystallinity. Effect of parameters was statistically validated and interpreted in accordance with FT-IR and TGAanalyses.Chemical treatment of solid cake resulted in lignin degradation which was followed by consecutive hemicellulosedecomposition. Cellulose crystallinity decreased at elevated time intervals due to detoriation of its structure. Results indicatedthe significance of time especially in decreasing cellulose crystallinity. Lignin content was decreased from 47% to 20-22%independent of conditions. In other words, lignin degradation was stable in investigated regions and it was concluded thatmildest conditions such as low temperature (30 ºC) and ammonia (NH3) (5%) would have been sufficient to achieve successfultreatment provided that the procedure be maintained for long time (12h) intervals. This was one of the highlights of this studyas it was shown that mildest conditions would have been adequate to achieve an effective treatment with energy conservationcompared to conventional methods still in use. NH3 treatment also enabled preservation of glucan in the structure which wasthe main problem in other treatment procedures. Results obtained from experiments indicated the presence of ß-glucan even inhighest treatment times.