Cracking the lignocellulosic code: Comparative insights into various pretreatment techniques for enhanced degradation in cattle manure

Abstract

High content of refractory lignocelluloses in cattle manure has long been a major bottleneck, severely hindering its anaerobic biogas production potential. In this study, a comparative analysis was conducted to evaluate the effects of thermal pretreatment, alkali pretreatment, and their combined approach on the degradation of lignocellulosic components within cattle manure. The results revealed that thermal-alkali pretreatment achieved the most significant improvement in lignocelluloses degradation, outperforming both alkali-only and thermal-only pretreatments, particularly in terms of lignin degradation. Notably, NaOH dosage was found to have a more pronounced impact on degradation efficiency than temperature. Under the most favorable pretreatment conditions, which involved a 2 % NaOH dosage and a temperature of 110 °C, the degradation efficiencies of hemicellulose, cellulose, and lignin reached 51.3 %, 26.5 %, and 45.7 %, respectively. This marked improvement led to the release of soluble biodegradable organics, including protein and carbohydrate, thereby enhancing the bioconversion potential in subsequent processes. Moreover, the release of ammonia and phosphate further elevated the possibility of efficient nutrients recovery, adding additional value to the pretreatment. Scanning electron microscopy analysis further revealed substantial alterations to the morphological characteristics of coarse fibers in cattle manure after the pretreatments, providing visual evidence of the enhanced degradation of lignocellulosic structure.