Improved Buffering Capacity and Methane Production by Anaerobic Co-Digestion of Corn Stalk and Straw Depolymerization Wastewater

Abstract

A new method has been developed to improve the buffer capacity and methane production of the anaerobic digestion of Corn Stalk (CS), in which both an anaerobic co-digestion of CS with Straw Depolymerization Wastewater (SDW) and a mono-digestion of CS at different substrate concentrations (25.9, 36.2 and 45.3 mg/L) were investigated. Batch assays were conducted under thermophilic conditions for 70 days, which showed that an anaerobic co-digestion significantly increased the buffering capacity and methane production of the digestion process. The lag time for methane generation resulting from an anaerobic co-digestion of CS with SDW was 10 days, while the lag time for a mono-digestion of CS was 23 days. A maximum methane production of 214.81 mL/g-VS was obtained for the anaerobic co-digestion of CS with SDW when the substrate concentration was 36.2 g/L, which was around 13.54% higher than for mono-digestion of CS of 189.20 mL/g-VS. The removal rate for sulfate increased from 10.43% to 58.40% when the substrate concentration was increased from 25.9 to 45.3 mg/L for the anaerobic co-digestion of CS with SDW. Microbial communities were analyzed using 16S rDNA sequencing technology which showed that anaerobic co-digestion of CS and SDW promotes the growth of methanogens. The relative abundance of these methanogens (Euryarchaeota) for the anaerobic co-digestion of CS with SDW was increased significantly, being approximately 8.25% higher than that of a mono-digestion of CS, which was at a substrate concentration of 36.2 g/L. This means that the anaerobic co-digestion of CS and SDW is beneficial for improving buffer capacity and methane production from the digestion of CS, with higher organic matter and sulfate removal rates also being obtained.

Keywords

• corn stalk
• SDW
• anaerobic co-digestion
• buffer capacity
• methane production