Anaerobic digestion of sugar beet pulp after acid thermal and alkali thermal pretreatments

In this study, biogas production was investigated in mesophilic conditions from sugar beet pulp (SBP). In untreated conditions, water dissolution rate was 15.5% and biogas production rate was 168.7 mL/g TS (total solid). Alkaline thermal pretreatments were applied at 100 °C with 3 N NaOH and KOH solutions. Amounts of alkaline and acid were added in an amount equal to 5%, 10%, 15%, 20%, and 30% of the solids in the reactor. Acid thermal pretreatments were applied at 100 °C with 5% (v/v) H₂SO₄ and HNO₃ solutions. The anaerobic digestion (AD) time was shortened by approximately 10 days after pretreatment. The highest biogas yield was 458.4 mL/g TS as a result of KOH thermal pretreatment. In this reactor, soluble chemical oxygen demand (sCOD) removal was 87.1%, and cellulose, hemicellulose, and lignin removals were 32.4%, 28.6%, and 33.5% w/w, respectively. It was observed that the cumulative biogas production (CBP) successfully fitted the modified Richards (MR) model and modified Gompertz (MG) model.