1. Collection efficiency and improper operation of the gas collection system,

2. Waste composition and the assumed Lo value can be different for other types of waste streams, and

3. Climate (moisture and temperature).

Dear Bolyard, Could you please mention the formula which includes climatic factors.

Methane is produced due to anaerobic decomposition of bio-waste. In natural SWM setting, it would depend on number of other factors like temperature, humidity, percentage composition of bio-waste. However, standard formulations might not always work out but you can use IPCC formulation to get theoretical quantification, even though researchers have also used other formulations like MTM and FOD. You can refer to Chakraborty et al. (2011) which reported extensive fieldwork from Delhi. 

doi:10.1016/j.atmosenv.2011.09.015

Thanks Somnath, my question is regarding the difference between experimental and modeling result. However, if you would have seen my research article " GHG emission and energy recovery potential from MSW landfill sites", you will find the lacuna in research done by Chakraborty et al. (2011). You go through my article for clarification. Good Luck

http://www.sciencedirect.com/science/article/pii/S2213138813000817

Dear Ashutosh

The Landfill Gas Emissions Model (LandGEM) is an automated estimation tool with a Microsoft Excel interface that can be used to estimate emission rates for total landfill gas, methane, carbon dioxide, non-methane organic compounds, and individual air pollutants from municipal solid waste landfills...

Goodluck

Thanks Rafiee!