Modelling methane and vinyl chloride in soil surrounding landfills

Sanitary landfilling is used in many countries as a preferred method for disposal of household wastes for reasons of simplicity and economics. Immediately following its deposition within a landfill, most of the organic fraction of waste will begin to undergo degradation through chemical and bacterial action. Landfill gas (LFG) is a product of biodegradation and consists of primarily methane (explosive) and carbon dioxide, with trace amounts of other volatiles that are often toxic gases (for example, vinyl chloride). LFG can migrate through the soil away from the landfill site and appear at the surface away from where it started. Since methane presents a fire or explosive threat, LFG must be controlled to protect property and public safety. To aid this, consideration must be given to models. Therefore, this study was undertaken to develop a simple numerical model by using a finite difference method in order to predict gas migration through the soil surrounding the landfill. The model construction was described as well as the landfill and its surrounding soil. The model was applied to predict methane and vinyl chloride concentrations at different distances from the landfill. Comparison between the predicted and measured values was calculated to evaluate the validity of the model. The agreement between measured and predicted concentrations was found, and this agreement is sufficiently good.