Emission factors are fundamental tools for air quality management. Odour Emission Factors (OEFs) can be developed in analogy with the emission factors defined for other chemical compounds, which relate the quantity of a pollutant released to the atmosphere to a given associated activity. Landfills typically represent a common source of odour complaint; for this reason, the development of specific OEFs allowing the estimation of odour emissions from this kind of source would be of great interest both for the landfill design and management. This study proposes an up-to-date methodology for the development of an OEF for the estimation of odour emissions from landfills, thereby focusing on the odour emissions related to the emissions of landfill gas (LFG) from the exhausted landfill surface. The proposed approach is an “indirect” approach based on the quantification of the LFG emissions from methane concentration measurements carried out on an Italian landfill. The Odour Emission Rate (OER) is then obtained by multiplying the emitted gas flow rate by the LFG odour concentration. The odour concentration of the LFG emitted through the landfill surface was estimated by means of an ad hoc correlation investigated between methane concentration and odour concentration. The OEF for the estimation of odour emissions from landfill surfaces was computed, considering the landfill surface as the activity index, as the product between the mean specific LFG flux emitted through the surface resulting from the experimental campaigns, equal to 0.39 l/m2/h, and its odour concentration, which was estimated to be equal to 105′000 eq. ouE/m3, thus giving an OEF of 0.011 ouE/m2/s. This value, which is considerably lower than those published in previous works, should be considered as an improved estimation based on the most recent developments of the research in the field of odour sampling on surface sources

The aim of this study is related to the assessment of odour emissions from landfill surfaces. Up to now, there is not a widely accepted method to quantify odour emissions from this particular kind of source. Five different methods were developed and investigated. These methods can be considered as based on three distinct approaches, both experimental and computational. The first approach provides to use models for the estimation the landfill gas production, whereby the second and the third approach are based on direct measurement campaigns on the landfill surface: for the determination of the methane concentration or for the direct measurement of the odour concentration, respectively. The methods were then compared in terms of specific odour emission rates by referring to other literature data. Finally, dispersion modelling was applied in order to allow a further comparison of the resulting odour impacts with other olfactometric data from independent monitoring campaigns on the studied site.

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Waste Water Treatment Plants are known to have significant emissions of several pollutants from the different treatment phases. Among such pollutants, volatile organic and inorganic compounds, often having low odour detection thresholds, cause odour nuisance to the population. One of the purposes of the present work is to determine which are the more suitable methodologies to assess the odour emissions from liquid passive area sources, by means of a thorough study of the models capable of describing the volatilization phenomena of the odoriferous compounds from such sources. Several different models were evaluated for the open field emission, selecting the most appropriate one. Moreover, the models describing volatilization under a forced convection regime inside a wind tunnel device have been investigated, in order to describe the situation inside this sampling device, typically used for sampling on liquid sources. By means of experimental tests involving pure liquid acetone and pure liquid butanone, it was verified that the model more suitable to describe precisely the volatilization inside the sampling hood is the model for the emission from a single flat plate in forced convection and laminar regime, with a fluid dynamic boundary layer fully developed and a developing mass transfer boundary layer. The proportionality coefficient for the model was re-evaluated in order to account for the specific characteristics of the adopted wind tunnel device. Due to the differences between the fluid dynamic conditions in the open field and inside the hood, it was deemed useful to devise a correlation that-according to the flush rate adopted inside the chamber-is capable of computing the wind velocity at a 10 m height that would cause the same emission flux that is estimated from the analysis of the sample collected with the wind tunnel. Finally, the field of application was clearly defined for the considered models during the project, discussing the two different kinds of compounds commonly found in emissive liquid pools or liquid spills, i.e. gas phase controlled and liquid phase controlled compounds.

The work focuses on the principles for the design of a specific static hood and on the definition of an optimal sampling procedure for the assessment of landfill gas (LFG) surface emissions. This is carried out by means of computational fluid dynamics (CFD) simulations to investigate the fluid dynamics conditions of the hood. The study proves that understanding the fluid dynamic conditions is fundamental in order to understand the sampling results and correctly interpret the measured concentration values by relating them to a suitable LFG emission model, and therefore to estimate emission rates. For this reason, CFD is a useful tool for the design and evaluation of sampling systems, among others, to verify the fundamental hypotheses on which the mass balance for the sampling hood is defined. The procedure here discussed, which is specific for the case of the investigated landfill, can be generalized to be applied also to different scenarios, where hood sampling is involved.