Fugitive emissions of biogas in coverage liner of compacted soil in a landfill

ABSTRACT Fugitive biogas emissions can represent a significant part of the gas flow in landfills, make the methane (CH4) energy use unfeasible, and also pose risks to the environmental health of the surrounding communities. In this context, this work aimed to evaluate the fugitive emissions and the factors that interfere in the biogas flow in the final landfill liner. The study area consisted of a Waste Cell, with a mass of 62,359.44 t of MSW deposited at the Campina Grande Sanitary Landfill, Paraíba, Brazil. In this Cell, measurements of the fugitive emissions of biogas were carried out, using the static chamber methodology; analysis of the concentration of gases at the soil-waste interface, using Gas Concentration Measurement Devices (CMD); and mapping of the gas emissions in the Waste Cell, applying data interpolation techniques based on Kriging. Flows of CH4 and carbon dioxide (CO2) ranging from 0 to 0.09 and 24.62 to 331.31 g.m-2.day-1, respectively. The percentage of retention of CH4 and CO2 by the liner was high, above 95%, being influenced mainly by the high degree of average compaction obtained for the Waste Cell (91.84%) and by the efficiency of the gas drainage system. The mapping of biogas emissions in the Waste Cell proved to be an important tool in the identification of the areas with the greatest potential for biogas generation and flow through the cover liner.

摘要 逸散性沼气排放可在填埋场气体流动中占据可观占比，不仅使得甲烷（CH4）的能源化利用难以实现，同时对周边社区的环境健康构成风险。在此背景下，本研究旨在评估填埋场终场防渗衬层中的逸散性沼气排放及干扰沼气流动的相关因素。本研究的研究区域为巴西帕拉伊巴州坎皮纳格兰德卫生填埋场内的一个填埋单元（Waste Cell），该单元内填埋了62359.44吨城市生活垃圾（Municipal Solid Waste, MSW）。在此填埋单元中，本研究采用静态箱法开展沼气逸散排放测量；利用气体浓度测量装置（Gas Concentration Measurement Devices, CMD）对土-垃圾界面的气体浓度进行分析；并基于克里金（Kriging）插值技术，对该填埋单元内的气体排放进行空间制图。结果显示，甲烷（CH4）与二氧化碳（CO2）的排放通量分别介于0~0.09 g·m⁻²·d⁻¹与24.62~331.31 g·m⁻²·d⁻¹之间。防渗衬层对甲烷（CH4）与二氧化碳（CO2）的截留率极高，可达95%以上，其主要受该填埋单元的平均压实度（91.84%）以及气体导排系统的运行效率影响。对该填埋单元内的沼气排放进行空间制图，可有效识别出沼气生成潜力最高以及气体易通过防渗衬层逸散的区域，是一项极具价值的分析手段。