Effect of organic loading, feed-to-inoculum ratio, and pretreatment on the anaerobic digestion of tobacco stalks

This work firstly investigated the suitable organic loading (OL) and feed to inoculum (F/I) ratio of three kinds of tobacco stalks (TS₁₁₆, TS₉₉, and TS₈₅) during anaerobic digestion (AD) via response surface methodology (RSM). The highest experimental methane yield (EMY) of 148.1 mL/g VS was achieved from TS₁₁₆ at OL of 20.2 g VS/L and F/I ratio of 1.1. To further increase EMY, various pretreatments including alkaline hydrogen peroxide (AHP), NaOH, KOH, Ca(OH)₂, HCl, and oxalic acid (H₂C₂O₄) were implemented on TS₁₁₆. Results showed that AHP was most effective, and the maximal EMY of 350.7 mL/g VS and biodegradability (B_d) of 81.4% were obtained from 7% AHP pretreated TS₁₁₆, which increased by 105.6% than untreated. XRD, FTIR, and SEM analyses evidenced that the structure of AHP pretreated TS₁₁₆ was strongly disrupted. This study lays the foundation for applying this waste into AD in future applications.