Modelling of anaerobic digester for the conversion of organic waste into hydrogen & methane

Abstract

Multistage Anaerobic digestion (AD) nowadays plays a beneficial role compared to single-stage AD to achieve a high rate of waste conversion with higher energy recovery. Hence, obtaining a stable operation with optimal operating conditions is of paramount importance in the modeling study. In the current study, modeling of two stages continuous stirred anaerobic digesters was considered using mass balances over the substrates (organic waste) and biomass in the respective reactor. All the simulation work was performed using MATLAB, from which steady-state concentration values were taken for the calculation of Hydrogen flow rate (QH2) and Methane flow rate (QCH4). The operating volumes of both the reactors were computed by looking at the effect on the production rates (QH2 &QCH4) as a function of dilution rate of first (D1) and second (D2) reactors for constant initial substrate concentration (S0). At last, the effect of Initial substrate concentration on both QH2 &QCH4 was studied by considering different S0 values as 4 g/L, 8 g/L, and 12 g/L. From our modeling result, it was found out that for Maximum Hydrogen production, operating D1 (in day-1) was 0.8, 0.9 & 1 and the Methane production rate was Maximum at operating D2 (inday-1) of 0.25, for S0 values of 4 g/L, 8 g/L, and 12 g/L respectively.