Fugitive Gaseous Emissions Characterization from Municipal Solid Waste Landfill by a New Integrated Approach: Field Surveys and Remote Sensing

Abstract

Municipal solid waste (MSW) landfills release different gaseous compounds in ambient air, including greenhouse gases and VOCs, with relevant effects in terms of contribution to global warming and odour annoyance. The accurate characterization and monitoring of these emissions is thus of fundamental importance to avoid negative impacts and for identifying and evaluating the effectiveness of mitigation measures. Currently, different and no universally accepted and standardized methods have been validated for the measurement of these emissions from landfill (landfill gas, LFG). The most widely-used techniques for the identification of emission rates from areal sources are known as “hood methods”. However, these methods are not particularly accurate for sampling LFG. Moreover, conventional approaches for LFG sampling frequently neglect the evaluation of fugitive emissions from crucial points of biogas network (i.e.: wells, drains, pipeline), which can be also interested by leakages and can thus result in significant emission of LFG into the atmosphere. For the abovementioned reasons, the development of specific methods for the assessment of the LFG emissions is of great interest to overcome the related issues. In the present work, an integrated and advanced approach for the monitoring and mapping of MSW landfill gas emissions has been presented and validated. The proposed procedure integrates multiple approaches to provide a complex and polyvalent survey of the landfill, also including the evaluation of the landfill terrain morphology and the presence of possible non-homogeneous areas. The experimental activities were carried out at a complex MSW landfill located in Central Italy (Lazio Region) and were organized into four steps: (i) identification and characterization of the fugitive emissions from landfill cover, by Flux Chamber device in different points of a geo-localized grid on landfill body; (ii) characterization of landfill terrain morphology and of possible fugitive emissions from biogas wells and other points considered relevant in the network, by using remote sensing with surveys implemented with drone equipped with RGB, multispectral and thermal cameras together with topographic measurements with GNSS receivers; (iii) integration of the geo-referenced results, including the Digital Terrain Model (DTM), the Normalized Difference Vegetation Index (NDVI), the thermographic mapping and the point monitoring results on landfill cover; (iv) elaboration of maps of the emissions levels for the different investigated compounds and the identification of critical points/areas. The results were elaborated and discussed (i) for the evaluation of the emissions from the investigated landfill, (ii) for proving the accuracy of the proposed procedure with cross-validation approaches and (iii) for extending the proposed procedure to a wider application for different types of landfills.