Enhancement of Biogas Production from Co-Digestion of Industrial Solid Pineapple Wastes by Two-Stage Anaerobic Digestion Systems

Abstract

This study aimed to investigate the biogas and methane production, as well as the COD removal efficiency by AD from pineapple solid wastes (PSW) as co-digestion feedstock. The two-stage of anaerobic digestion system was configured as continuously stirred tank reactor (CSTR) installed with anaerobic hybrid reactor (AHR) in order to enhance the efficiency and stability in biogas production. The PSW were firstly characterized for chemical composition. Then, the total solids (TS) were controlled as 4% of TS in influent loadings and four different HRTs were determined to investigate the subsequent effects, such as pH, total volatile acids and alkaline (TVA/Alk) ratio, biogas and methane production, and COD removal efficiency. The results demonstrated that the overall pH condition in CSTR was more acidic than AHR system and simultaneously performed in less stability of AD process by presence of massive TVA/Alk ratio. Furthermore, the maximum biogas production and COD removal efficiency were also observed in AHR system at 2,702 mL and 80.53% under HRT7 and HRT15, respectively. Interestingly, more than thousand millilitres of biogas production were dramatically increased from CSTR system under parallel operation. Thus, the separated acidogenic and methanogenic stage in two-stage system obviously improved the potential of AD process. However, the methane yields in AHR system remained stable in the range of 0.16-0.19m3/kgCOD removed, excepted at the lowest HRT condition (HRT5) by increasing OLRs. Thus, the optimal conditions for biogas production and COD removal could be varied, which depending on the types of feedstocks and operational reactors.