Co-pretreatment of wheat straw by potassium hydroxide and calcium hydroxide: Methane production, economics, and energy potential analysis.

To improve the methane production of wheat straw (WS), the mono-pretreatment (MP) and co-pretreatment (CP) of WS with KOH and Ca(OH)2 were conducted in this study. The results showed that the MP with KOH presented better effects than the MP with Ca(OH)2 . However, the CP with 2% KOH combined with 1% Ca(OH)2 displayed similar effects to those of the MP with 3% KOH, obtaining the cumulative methane yield of 239.8 mL gVS -1 and an improved biodegradability from 56.37% of raw WS to 66.10%. Methane production and kinetic analyses suggested that 2% KOH combined with 1% Ca(OH)2 was the ideal condition of alkaline pretreatment for anaerobic digestion of WS. The mechanism for the improvement in methane production was clearly described by biochemical component, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analyses. Moreover, preliminary economics and energy potential analyses also confirmed that alkaline co-pretreatment was a reasonable method, which not only gave important guidance for future utilization of WS waste but also showed useful reference for the efficient pretreatment of other lignocellulosic wastes.