Enhanced methane production from wool textile residues by thermal and enzymatic pretreatment

Abstract

Methane production from two types of wool textile wastes (TW1 and TW2) was investigated. To improve the digestibility of these textiles, different pretreatments were applied, and comprised thermal treatment (at 120°C for 10min), enzymatic hydrolysis (using an alkaline endopeptidase at different levels of enzymatic loading, at 55°C for 0, 2, and 8h), and a combination of these two treatments. Soluble protein concentration and sCOD (soluble chemical oxygen demand) were measured to evaluate the effectivity of the different pretreatment conditions to degrade wool keratin. The sCOD as well as the soluble protein content had increased in both textile samples in comparison to untreated samples, as a response to the different pretreatments indicating breakdown of the wool keratin structure.The combined treatments and the thermal treatments were further evaluated by anaerobic batch digestion assays at 55°C. Combined thermal and enzymatic treatment of TW1 and TW2 resulted in methane productions of 0.43Nm3/kg VS and 0.27Nm3/kg VS, i.e., 20 and 10 times higher yields, respectively, than that gained from untreated samples. The application of thermal treatment by itself was less effective and resulted in increasing the methane production by 10-fold for TW1 and showing no significant improvement for TW2.