Mathematical modeling and simulation of methane gas production in simulated landfill column reactors under sulfidogenic and methanogenic environments

Abstract

A mathematical model was developed to simulate methane and carbon dioxide production from simulated landfill column reactors operated under sulfate reducing and methane producing conditions. The model incorporated governing equations which describe the chemical and biochemical processes responsible for the degradation of organic waste materials. These processes were hydrolysis, acidogenesis, methanogenesis and sulfidogenesis. The differential equations were numerically solved using Stella Researcher Software. The model was calibrated and verified using 700 days of gas production data from the simulated landfill column reactors. The calibrated hydrolysis rate constants for newspaper and sludge were found to be higher in sulfate reducing reactors as compared to methane producing reactors. The simulated methane production was quite accurate in all the reactors, but the predicted carbon dioxide production in the sulfate reducing reactors was not so accurate for the first 100 days, which may be attributed to the necessity of further governing equations. According to the sensitivity analysis, hydrolysis rate constants and moisture factors were the two most sensitive parameters controlling the gas production.