Oyster shell as pH control substitute for two stage anaerobic co-digestion system

抄録

Anaerobic digestion (AD) can convert organic waste into energy by utilizing microbiological processes. Nevertheless, this system with two-stage configuration still experiences an issue, particularly pH drops. To create a low-carbon energy system, we evaluate the performance of crushed oyster shells as alkaline substitutes in two-stage anaerobic digesters. The result shows that control treatment using alkali has the highest VS (1.18%) and COD (27.7 g/L). Oyster shell treatment has lower VS (1.14%) and COD (25.01 g/L). As a result of comparing greenhouse gas (GHG) emissions in using NaOH and oyster shells by the LCA method, the equivalent weight of CO₂ emission from the oyster shell is 0.15 times of alkali. In the methanogenesis stage, alkali treatment produced 24% higher methane gas yield in the highest OLR (422.01 mlCH₄/gVS in 2.6 gVS/L/day) compared to oyster shell treatment (321.32 ml CH₄/gVS in 2.8 gVS/L/day). Highest methane gas percentage produced from alkali treatment (77.53%), while in oyster shell treatment highest methane gas percentage is 71.11%. Alkali treatment performs better in methane gas production using two-stage anaerobic digesters, but oyster shells offer advantages in terms of practicality, stability, and environmental impact.