Analysis of the efficiency of first-order decay models in forecasting greenhouse gas emission in Brazilian sanitary landfills

ABSTRACT The objective of this study was to evaluate the efficiency of first-order models for prediction of biogas emission in landfills, comparing forecasts with observations registered along the years of landfill operation. The landfills analyzed in this research operate within Clean Development Mechanism (CDM) that may receive financial incentives - certified emission reductions or carbon credits. Four Brazilian landfills (Nova Iguaçu, Paulinia, Caieiras and Bandeirantes) have been selected, for which the annual quantities of waste actually deposited during the first seven-year period of carbon credits were available, thus eliminating a major source of uncertainty in the forecasting models. Limitations of the models of the first order recommended by the guidelines of the Intergovernmental Panel on Climate Change (IPCC) are discussed, including intrinsic errors in the mathematical formulation and misinterpretation of the starting time for prediction of biogas emission. It is also proposed a modification in the CDM Tool model, currently used for biogas emission in solid waste deposits operating as CDM projects.