CALMIM (California Landfill Methane Inventory Model) is a field-validated 1-dimensional transport and oxidation model that calculates annual site-specific landfill methane emissions based on the major processes that control emissions:

• Surface area and properties of the daily, intermediate, and final cover materials,
• The % of surface area for each cover type with engineered gas recovery, and
• Seasonal methane oxidation in each cover type as controlled by climatic factors.

The driving force for emissions is the methane concentration gradient through each cover type coupled with typical annual soil moisture and temperature profiles which control methane transport and microbial methane oxidation over an annual cycle. CALMIM is an IPCC (Intergovernmental Panel on Climate Change) Tier III model for methane emissions from solid waste disposal sites.

The climate-related factors (meteorology and soil microclimate) are automatically accessed based on the site location and physical properties of the cover materials. This model is intended to be userfriendly with a series of input boxes where the user enters basic information on the areas and properties of daily, intermediate, and final cover materials, as well as the % surface area for each cover type with engineered gas recovery (either vertical wells or horizontal collectors). CALMIM calculates daily emissions for each cover type which are summed to provide an annual total for the site, both in units of g methane/square meter/day (g CH4 m-2d-1) and for the site as a whole. Taking into consideration recent literature which indicates that first order kinetic models for theoretical methane generation do not match field measurements for landfill methane emissions, CALMIM is the first landfill methane emissions model which does not rely on a first order model for methane generation based on the mass of waste in place.

CALMIM was developed during 2007-2010 with supporting laboratory studies and field validation under the auspices of the California Energy Commission PIER (Public Interest Energy Research) Program. CALMIM is JAVA-based, freely available to users, and is intended to be the first step in the development of improved science-based models which have been field-validated and can be internationally applied to landfill methane emissions inclusive of seasonal methane oxidation.