CO2 and CH4 Flux Measurements from Landfills - A Case Study: Gualeguaychú Municipal Landfill, Entre Ríos Province, Argentina

ROMINA SANCI Y HECTOR PANARELLO

Greenhouse Gases - Emission, Measurement and Management

InTech

Año: 2012; p. 255 - 272

Municipal solid waste (MSW) landfills are used to dispose of household wastes: food and garden waste, paper, metal, glass, wood, textiles, rubber, leather, plastic, ash, dust and electronic waste. Decomposition of landfilled MSW by long-term physicochemical, chemical and biological processes causes dissolution or decay of landfill materials and production of leachate and gases. In particular, bacterialdecomposition of the biodegradable fraction of MSW generates mainly methane (CH4) and carbon dioxide (CO2) as well as a wide variety of minor and trace components: hydrogen,water vapor, hydrogen sulfide, ammonia, and volatile organic compounds. In spite of efforts being made to control landfill gases (LG) - gas containment, collection and utilisation, flaring and treatment- ,these are usually released into the atmosphere directly and indirectly, from the ground or via sub-surface gas migration, respectively. These LG emissions into the atmosphere represent potential hazards that are of concern locally, regionally and globally. The trace components of LG pose an odour and toxicity risk (although CO2 is also toxic if it is present in high enough concentrations). Explosion and asphyxia risk is related to sub-surface migration and accumulations in enclosed spaces. Root zone displacement of oxygen by landfill gas is the most likely cause of local ecotoxicity. In addition, volatile organic compounds (VOC) have detrimental effects on human health and they participate in photochemical pollution as precursors of tropospheric ozone. CO2 and CH4 are greenhouse gases and contribute to global warming. Landfills have been implicated as being the largest anthropogenic sources of atmospheric CH4 in the world, comprising about 11% of the total anthropogenic global CH4 contribution. Direct measurements of CH4 and CO2 emissions from ground to atmosphere are used as an effective tool to estimate the degassing rate of individual sources and to calibrate global Earth degassing estimates. Early studies of diffuse degassing, focus on the flow of CO2 out of the soil, commonly called CO2 ‘‘flux’’ or ‘‘efflux’’ and expressed as [mass] [area] -1 [time] -1, they were developed in agricultural or ecological areas to measure soil respiration or the flux from soil of other gaseous species.Later, they were applied in active volcanic-geothermal environments where CO2 is derived from some geologic source at depth. In this chapter, we summarize all the steps involved in the process of the quantifying of CO2 and CH4 fluxes (background, measurement methods calibration, geostatistical treatment of results, presentation of data) from landfills, and its application in Gualeguaychú Municipal Landfill, Entre Ríos province, Argentina. The method of determining the biodegradation processes of solid wastes by extracting gases with a probe and analyzing carbon isotopes on those gases is also included in the text. In addition, the dissolution of these gases in shallow aquifers is evaluated since in the case study that we present the groundwater acts as a sink for the CO2 that is developing in the landfill.