Mathematical modeling of a biogas recovery system at the İZAYDAŞ, Kocaeli sanitary landfill

Abstract

The purpose of this study is to asses the potential of landfill gas generation and recovery from Lot 7 of the İZAYDAŞ solid waste disposal site in Izmit, Turkey. A multi-step model is developed to evaluate the performance and aid in the operation of an active gas collection system for Lot 7. The model consists of three main components: a water balance model, HELP; a gas generation model, LANDGEM; and a gas flow model, MODAIR, based on the MODFLOW computer program. The results of this study indicate that the main factors influencing the efficiency of the gas collection system are: decay rate of the organic component of the solid waste, the mode of operation of the active gas collection system, the air permeability of the soil cover. Specifically, the decay rate controls the duration of the most active gas generation period and the required extraction rates to capture the generated gases. Time-dependent gas extraction rates, as opposed to time-invariant extraction rates, was shown to lead to reduced gas losses into the atmosphere and higher landfill gas concentration in the collected gas. Moreover, the use of low permeability soil cover can also lead to reduced air intrusion into the collection system.