Modelling of landfill gas generation: a review

Landfill gas generation models apply utilizes several different parameters to project Methane (CH4) generation from a specific mass of disposed waste over a time period in a landfill site. These models are used for better estimating the size of landfill gas (LFG) collection systems, monitoring objectives, assessments, and prognostications. Compared to other options to estimate and control LFG production (such as the application of the test wells), models offer advantages due to the relatively prompt results and cost-effectiveness. Over the recent years, developing LFG generation models has become precedence for the LFG industry. The main trouble in designing and operating an LFG collection system is the uncertainty of LFG generation rates. The LFG generation rates are presently measured via models associated with the waste disposal history, moisture content, gas collection systems, and cover type, which have significant uncertainties. From literature studies, there is not sufficient data regarding the comparison between different models or calibrating them with CH4-filled landfill data and the CH4 generation and recovery models are not adequately progressive. The purpose of this study is to provide a comprehensive review of the commonly used models that predict LFG generated in landfill sites as well as discuss their specific characteristics. As a result, these numerical models are categorized in mathematical, numerical, and zero-, first-, and second-order decay models. Since first-order decay models are extensively used throughout the world, their consideration as multiphase models to make more appropriate projections is discussed in more detail.