Analisi e caratterizzazione delle emissioni dagli impianti di smaltimento rifiuti e studio di tecnologie innovative di mitigazione degli impatti

Landfilling is still the most widely used form of disposal of MSW in Europe. Eurostat (2015) reports that in 2013, with reference to the 28 member states, about the 31% of MSW produced were disposed of in landfills. The same data is estimated at national level; in Italy, with reference to 2013, the MSW disposed in landfill amounted to the 31% of the produced waste (ISPRA, 2015). One of the main environmental challenges associated with landfills is the generation of LFG produced by the anaerobic decomposition of the organic waste fraction. LFG is mainly composed by methane (CH4) and carbon dioxide (CO2), and its production lasts until the majority of the organic material in the waste is degraded, which can take several decades. As is common knowledge, suboptimal cover design and improper landfills management can lead to undesired LFG emissions. For this reason, landfills are considered significant anthropogenic sources of odours and greenhouse gases. This thesis deals with impact of emission produced from the disposal of MSW in landfill and innovative mitigation technologies. The role of landfill in modern waste management system as well as the related environmental problems are discussed in Chapter 1. Furthermore, the basic principles of the microbial methane oxidation process as a mitigation strategy for landfill methane emissions are described. Chapter 2 addresses investigations with monitoring field campaigns to study the emissions from a waste management site. The different sources present in the study case are compared in order to identify the main environmental issues. In particular, the diffusive emissions from the landfill covers, the emissions from the mechanical biological treatment plant and the emissions from the landfill gas recovery plant are compared both in terms of magnitude and in terms of emitted compound. In Chapter 3 the results derived from a project performed in collaboration with a landfill manager and the environmental protection agency of Tuscany are presented. The main objective of the study is to assess if the undesired odour emissions during waste disposal is due to sensory characteristics of waste or to degradation processes that may occur already in the early phase of disposal. The study was conducted on samples on MSW compost from mechanical biological facilities and sludge from wastewater treatment plants. The study was performed through different phases: monitoring on the daily cover to assess the emission rates during disposal; characterization of waste, particularly determination of biological stability parameters; study of the possible reactivation of aerobic or anaerobic degradation processes in waste samples with specific lab tests (controlled batch reactors); chemical analysis of compounds emitted during the tests. Chapter 4 provides insight into the microbial methane oxidation of landfill gas as innovative technology to reduce landfill impact. The chapter presents results of both field and laboratory investigations. In particular it reports the results derived from the monitoring of a pilot bio-covers system implemented in a Tuscan landfill to assess the capacity of methane oxidation in different substrates, particularly compost from source-selected organic fraction, MSW compost from mechanical biological facility and mixed compost. The substrates were characterized by several biological and chemical-physical parameters. The oxidation efficiency of the biocovers was determined by gas and temperature profiles, calculated methane oxidation rates using a mass balance as well as landfill gas flux measurements. Furthermore, some laboratory column tests were carried out in order to assess the performance of the materials used in the field test with a known inlet biogas flow.