EVALUATION OF THE EFFICIENCY OF ALKALINE PRETREATMENT OF RYE STRAW FOR POTENTIAL SECOND-GENERATION LIQUID BIOFUEL PRODUCTION

Abstract

The present study investigates the potential of rye straw as a feedstock for second-generation bioethanol production, addressing the growing need for sustainable energy solutions in Ukraine and aligning with European Union renewable energy directives. Traditional first-generation bioethanol relies on food-grade feedstocks, posing limitations due to competition with food resources. In contrast, lignocellulosic residues such as rye straw are non-food biomass, offering an environmentally friendly alternative. The rye straw contained 42.3 % cellulose, 30.3 % hemicelluloses, and 19.6 % lignin, making it highly suitable for conversion into fermentable sugars. This study focuses on the optimization of alkali pretreatment to maximize cellulose recovery and reduce residual lignin, thereby producing a substrate suitable for further processing. Alkaline treatment at 120 °C provides a favorable compromise between high product yield and efficient delignification. A factorial experimental design was employed to evaluate the effects of NaOH concentration and treatment time on substrate yield, cellulose content, and lignin removal. The selectivity of delignification, used as an integrated indicator of lignin removal and carbohydrate preservation, reached approximately 85 % at 6 % NaOH and 55 min of treatment, while multi-criteria optimization using the Harrington desirability function identified 6 % NaOH and 35 min as the optimal conditions providing the best balance between substrate yield, cellulose enrichment, and lignin reduction. This research contributes to the potential development of cost-effective, and environmentally sustainable biofuel production processes, supporting Ukraine’s energy transition and the advancement of the circular bioeconomy. Bibl. 36, Tab. 3, Fig. 3.