Biomethane production kinetics of rumen pretreated lignocellulosic wastes

Abstract

Bioenergy production from lignocellulosic biomass is challenging due to its complex structure. Therefore, a pretreatment is required before methane production. Studies investigating the pretreatment of lignocellulosic waste using rumen fluid are limited and focused only on a certain waste. In this study, pretreatment by rumen microorganisms was applied for different types of lignocellulosic wastes: wheat straw, cotton stalk, reeds and sunflower stalk. The reactors containing 1 g waste were pretreated for 2, 5, 10, 15 and 20 days to investigate optimum pretreatment time for methane production. After the pretreatment stages and gas measurements, reactors were separated into two phases as solid phase and liquid phase. The reactors were installed for the anaerobic digestion; gas measurements were made cumulatively. Modified Gompertz equation was used to estimate potential biogas production. The maximum biogas productions were obtained in 2 days pretreatment of wheat straw, reeds and sunflower stalk with 1.2 to 1.4-fold increase compared to non-pretreated wastes. Maximum increase in biogas amount of 1.3-fold was obtained in 5 and 10 days pretreated cotton stalk compared to non-pretreated cotton stalk. The highest methane yield was obtained in 5 days pretreated wheat straw with 101.7 ml methane. The maximum methane yield was followed by reeds waste pretreated for 20 days with 76.15 ml, sunflower stalk pretreated for 2 days with 52 ml, and cotton stalk pretreated for 2 days with 50 ml methane. Rumen pretreatment had positive effects in the production of methane from different lignocellulosic wastes, depending on the pretreatment time. It has been suggested to examine the effect of rumen on methane and other fuel productions from other wastes.