Análise das estimativas de emissão de metano por aterros sanitários em projetos de MDL no Brasil.

Abstract

Most of the Brazilian municipalities find the installation of a Solid Waste Disposal Site a challenge due to the high investment needed. There are some ways to mitigate these costs, including emissions trading. With previous planning, it is possible to burn the methane produced by the decomposition of the waste, resulting in benefits for the landfill by either the simple use of the gas (generating electricity or directly selling the gas) or the revenues from negotiations of emissions certificates. Included in previous planning is the ex-ante estimation of the methane produced by the landfill in order to know beforehand how to make the best use of the biogas and the amount of revenues that can be obtained from this use. When the CDM projects developed in landfills are analyzed, it can be noticed that these estimations generally are poorly made, resulting in estimated values far above the real methane production. This mistake results in a credibility loss by this type of project, since the expected number is rarely achieved. There are some factors that contribute to this difference in values, being operational problems (such as deficiency in the biogas capture and problems in the collection and recirculation of the leachate) and modeling problems (such as the use of input values obtained from experiments in laboratories under different situations from the ones found in Brazilian landfills) the major issues. The present work aims to present and discuss the main problems in estimating ex-ante the methane produced by landfills, using Brazilian CDM projects that are registered and issuing carbon credits as sources to analyze the quality of estimations currently being made. Additionally, experts in landfills and estimations are interviewed in order to obtain different points of view. It is clear that the estimated values, in general, are between 40 and 50% higher than observed during the operation of the landfill. Half of the experts point operational problems as the main contributors, however modeling problems seems to have a decisive influence in estimations. The use of input values must be carefully analyzed and must be used numbers obtained through researches that represent the reality of the landfill in question.