Theevaluation of the biogas potential of lignocellulosic wastes subjected to the enzymatic hydrolysis

Abstract

The aim of the study was to analyze the influence of enzyme preparation in the solution of solid wastes with different degree of affinity and resistance on hydrolysis (grass, straw, sawdust) as well as on the increase of biogas production. The lignocellulosic wastes were pre-treated using commercial preparation with cellulolytic enzymes or using enzyme from moldy bread. The study was carried out in the 50 L fermentation chamber model, the volume of biogas production was measured for 72 hours after the feedstock was introduced. The changes in some parameters of solutions of lignocellulosic pulp (LCW) and fermentation sludge (pH, COD, TS, VS) were also analyzed. The test results showed that 4-50% increase of COD and lower pH in waste solutions was obtained after the enzyme addition. The amount of biogas obtained per 1 kg VS of pure LCW was 10-975 L, yet after the enzyme application, it increased by as much as 130%. The largest biogas potential was obtained for grass-wastes but the influence of enzyme on this substrate was the lowest. The cyclic introduction of the investigated lignocellulosic pulp into the fermentation chamber had neither negative effect on the fermentation process nor significantly altered the fermentative sludge parameters. Moreover, enzymatic pre-treatment improves the degree of sludge mineralization. During 3 months of the study, the content of VS in the dry matter decreased from 71.8% to 39.3%.