Odour Emission Factor Research Articles

Odour Emissions from Livestock Buildings

Due to the intensification and concentration of agriculture and the interpenetration of residential and agricultural areas, odours are an important air pollutant. The changes taking place in rural areas mean that not all inhabitants of these areas are involved in agricultural activities, and there are new people looking for an idyllic life in the countryside. In recent years, there has been an increase in the number of complaints concerning odour emissions from agricultural sources. The aim of the study was to compare odour emissions from selected livestock buildings for various animal species in the Great Poland Voivodeship. The assessment of odour concentrations was made in accordance with EN 13725: 2003 using the TO 8 olfactometer in the accredited olfactometric laboratory of the Institute of Technology and Life Sciences National Research Institute in Poznań. The fattening house showed the highest odour burden for the surroundings (mean odour concentration and odour emission factor: 450 ouE·m3 and 0.419 ouE·s−1·kg−1, respectively). In the case of buildings for poultry and dairy cows, the differences in the emission factors were not large. The emission factor for poultry (0.232 ouE·s−1·kg−1) was 22% higher than that for dairy cows (0.190 ouE·s−1·kg−1). Conversely, the mean concentration in the hen house (281 ouE·m3) was 18% lower than that in the dairy cow barn (342 ouE·m3).

Assessment of odour emissions by the use of a dispersion model in the context of the proposed new law in Chile

Chile is looking to define a regulatory framework for the odour emissions of various critical industrial activities. One of these is the sanitary sector, with 300 wastewater treatment plants (WWTP). The basis currently used by the Chilean environmental authority to assess odours is the set of odour emission factors (OEF) taken from the Dutch standard. The aim of this study was to compare these, used as a national reference, with our own OEF calculated from measurements using dynamic olfactometry of 41 WWTP. The dependence of OEF on operational variables such as flow rate and BOD5 was analysed in different plant processes. The current regulations were assessed under the two OEF scenarios for the 95th, 98th and 99.9th percentiles in the Temuco WWTP, using the WRF-CALPUFF modelling protocol. The OEF values of the emission sources showed no strong correlation with operating variables like BOD5 and wastewater flow rates in all plant sections. Our OEF values based on real measurements presented significant differences from the Dutch reference OEF, of the order of 6 UOe/m2/s. The odour emitting-units with the largest differences were the pre-treatment units, flow-splitting chamber and most units of the sludge processing sections. These new OEF offer an alternative paradigm for measuring emissions and an incentive to more accurate calculation of the emissions in critical units such as sludge treatment lines. When the WWTP studied in Temuco was assessed using the OEF calculated in this study, a difference of 1041 OUe/s was found above the odours emissions calculated using the Dutch reference database. Using the Dutch OEF, the odour immission concentrations at nearby receptors were not exceeded for the 95th and 98th percentiles; this might result in deficient environmental assessment under current Chilean laws. We therefore recommend that Chilean institutions should assess projects using the OEF calculated in this study.

Characterization of the Gaseous and Odour Emissions from the Composting of Conventional Sewage Sludge

Many different alternatives exist to manage and treat sewage sludge, all with the common drawback of causing environmental and odour impacts. The main objective of this work is to present a full inventory of the gaseous and odorous emissions generated during the bench-scale composting of conventional sewage sludge, aiming at assessing the process performance and providing global valuable information of the different gaseous emission patterns and emission factors found for greenhouse gases (GHG) and odorant pollutants during the conventional sewage sludge composting process. The main process parameters evaluated were the temperature of the material, specific airflow, average oxygen uptake rate (OUR), and final dynamic respiration index (DRI), resulting in a proper performance of the sewage sludge composting process and obtaining the expected final product. The obtained material was properly stabilized, presenting a final DRI of 1.2 ± 0.2 g O2·h−1·kg−1 Volatile Solids (VS). GHGs emission factor, in terms of kg CO2eq·Mg−1 dry matter of sewage sludge (DM–SS), was found to be 2.30 × 102. On the other hand, the sewage sludge composting odour emission factor (OEF) was 2.68 × 107ou·Mg−1 DM–SS. Finally, the most abundant volatile organic compounds (VOC) species found in the composting gaseous emissions were terpenes, sulphur compounds, ketones, and aromatic hydrocarbons, whereas the major odour contributors identified were dimethyldisulphide, eucalyptol, and α-pinene.

The Impact of Microclimate Parameters on Odour Emissions from Pig Production in Spring

Abstract The aim of this study was to examine the impact of inside temperature and relative humidity, ventilation rate and gas concentrations (NH3, N2O, CO2) on odour emissions from deep-litter piggery. The studied facility had temperature-controlled mechanical ventilation. The measurements were conducted from March to June 2014. During the research, selected microclimate parameters, as well as number and mass of animals were monitored and air samples were collected (two samples of air in each series of measurements). Temperature and relative humidity were measured using Testo 435-4 multifunctional measuring instrument. To measurements of gas concentrations was used the photo-acoustic spectrometer Multi Gas Monitor Model 1312. The concentration of odours in the air samples was determined by dynamic olfactometry with the TO 8 olfactometer, according to PN-EN 13725:2007. The odour concentration ranged from 450 to 2004 ouE · m–3 (mean 1048 ouE · m–3) and the mean odour emission factor was from 5.76 to 46.79 ouE · (s · pig)−1 (mean 20.93 ouE· (s · pig)−1.The statistical analysis showed that the inside temperature explained most of the variability of the odour concentration and the relationship was described by equation: cod = 5634 – 197 Tinside (R 2 = 0.82, p ≤ 0.05). For odour emission factor, two parameters: the inside temperature and ventilation rate, explained most of the variability, according to the equation: EFod = 108 + 1939 VR – 5.5 Tinside (R 2 = 0.81, p ≤ 0.05).

Developing an odour emission factor for an oil refinery plant using reverse dispersion modeling

Odour emission factors (OEFs) for oil refineries are useful data for estimating odour emission rates (OERs) of different odour emission sources at oil refineries and developing odour emission inventories with lower cost and time than direct sampling and measurement method. The conventional direct source measurement followed by olfactometry sometimes faces challenges due to access issues and the presence of fugitive emissions for which determining emission rates is difficult. To address these issues, applying reverse odour dispersion modeling could be an appropriate alternative method in estimating OERs of oil refineries and developing OEFs; however, very limited research has been conducted and the level of their accuracy and reliability has not been well investigated. This study obtained OEFs for different sources of a conventional oil refinery plant in Canada using odour reverse dispersion modeling technique with AERMOD, a US EPA regulatory dispersion model. The results showed that the main odour sources at the oil refinery are tall stacks with the share of 99% of odour emissions while passive and fugitive emissions contribute to 1% of the odour emissions of the refinery. Results also demonstrated that the reverse odour dispersion modeling by AERMOD is an appropriate method of estimating OERs as the results of this study are within the ranges reported by previous similar research. Using reverse modeling, a total OER of 1,527,471ou/s was found for the entire oil refinery leading to an OEF of 910,162 ou/barrel which can be used by conventional oil refineries to estimate their odour emission inventories according to their capacity.

Filling in sewage sludge biodrying gaps: Greenhouse gases, volatile organic compounds and odour emissions

In the present work, a complete study of the sewage sludge (SS) biodrying technology was conducted at bench-scale, aiming at assessing its performance and providing a valuable insight into the different gaseous emission patterns found for greenhouse gases (GHG) and odorant pollutants. As process key parameters, temperature, specific airflow, dynamic respiration index, final moisture content and Lower Calorific Value (LCV) were evaluated. At the end of the biodrying, a product with a 35.9% moisture content and a LCV of 7.1 MJ·kg−1product was obtained. GHGs emission factor was 28.22 kgCO2eq per Mg of initial mass of dry matter in the SS (DM0-SS). During the biodrying process, maximum odour concentration measured was 3043 ou·m−3 and the estimated odour emission factor of the biological treatment was 3.10E + 07 ou per Mg DM0-SS. Finally, VOCs were completely identified and quantified. The most abundant VOCs found in the biodrying gaseous emissions were terpenes, sulphur-compounds and ketones.

A systematic study on the VOCs characterization and odour emissions in a full-scale sewage sludge composting plant.

Sewage sludge management is known to cause odour impact over the environment. However, an information gap exists about odour emissions quantification from different treatment strategies. In the present work, odorous emissions generated in a full-scale sewage sludge composting plant were characterized, aiming at providing specific odour emission factors (OEF) and to determine their variability depending on the composting time. Additionally, characterization of VOCs emitted during the process was conducted through TD-GC/MS analyses. Odour emission and VOCs characterization considered both (1) a first stage where a raw sludge and vegetal fraction mixture were actively composted in dynamic windrows and (2) a second curing stage in static piles. After increasing the composting time, a reduction of 40% of the maximum odour concentration referred to the dynamic windrow stage was estimated, whereas a reduction of 89% of the maximum odour concentration was achieved after turning of curing piles. However, global OEF increased from 4.42E + 06 to 5.97E + 06 ou·Mg-1 RS - VF when the composting time increased. Finally, different VOCs such as isovaleraldehyde, indole, skatole, butyric acid, dimethyl sulphide and dimethyl disulphide were identified as main potential odour contributors. Results obtained are a valuable resource for plant management to choose an appropriate sewage sludge composting strategy to mitigate odour emissions.

Chemical and odor characterization of gas emissions released during composting of solid wastes and digestates

Hazardous and odorous gas emissions from composting and methanization plants are an issue of public concern. Odor and chemical monitoring are thus critical steps in providing suitable strategies for air pollution control at waste treatment units. In this study, 141 gas samples were extensively analyzed to characterize the odor and chemical emissions released upon the aerobic treatment of 10 raw substrates and five digestates. For this purpose, agricultural wastes, biowastes, green wastes, sewage sludge, and municipal solid waste (MSW) were composted in 300 L pilots under forced aeration. Gas exhausts were evaluated through dynamic olfactometry and analytical methods (i.e., GC/MS) to determine their odor concentration (OC in OUE m−3) and chemical composition. A total of 60 chemical compounds belonging to 9 chemical families were identified and quantified. Terpenes, oxygenated compounds, and ammonia exhibited the largest cumulative mass emission. Odor emission rates (OUE h−1) were computed based on OC measurements and related to the initial amount of organic matter composted and the process time to provide odor emission factors (OEFs in OUE g−1OM0). The composting process of solid wastes accounted for OEFs ranging from 65 to 3089 OUE g−1OM0, whereas digestates composting showed a lower odor emission potential with OEF fluctuating from 8.6 to 30.5 OUE g−1OM0. Moreover, chemical concentrations of single compounds were weighted with their corresponding odor detection thresholds (ODTs) to yield odor activities values (OAVs) and odor contribution (POi, %). Volatile sulfur compounds were the main odorants (POi = 54–99%) regardless of the operational composting conditions or substrate treated. Notably, methanethiol was the leading odorant for 73% of the composting experiments.

Bituminous Conglomerates Industrial Production. Assessment of Odour Emissions in View of Regional Guidelines Publication

In Italy the production of bituminous conglomerates (BC) has no specific guidelines for odour emissions. Bitumen fumes contain particulates, hydrocarbons (VOC) and hydrogen sulphide (H2S) and the quantity of fumes depends on bitumen quality, the handling and storage of the bitumen and inert material. Different VOC formation, including odorants, depends on various parameters such as the asphalt temperature, the asphalt oxidation, and the humidity of air, and large variations are observed under different operational parameters. Currently authorizations and permits for binder and hot mix plants are generally limited to pollutants in stack emissions, like particulate matter (PM), total hydrocarbons (THC) and polycyclic aromatic hydrocarbons (PAH). Like other industrial activities, BC production plants are facing increasing difficulty in coexistence with residents in the vicinity of production facilities due to odour emissions (Palmiotto et al., 2014).Production plants use different technologies and odour emissions occur not only through the stack, were fumes coming from hot mixing of a bituminous binder with mineral stone sand and filler are emitted, but also from diffuse uncontrolled emissions, due to storage and handling operations of bitumen at high temperatures.In this work we present data from different monitoring campaigns focussed on odour emissions from hot mix asphalt (HMA) manufacturing facilities, that will be used to quantitatively describe this specific industry sector or category, i.e. a group of similar emitting sources. The final objective will be the definition of emission factors regarding HMA odour emissions, possibly also with a specific odour emission factor estimated per tons of product in view of the possible publication of Lombardy Regional Guidelines on HMA odour emissions characterization and mitigation.

Estimating the odor emission factors of the grit removal chambers of publicly-owned wastewater treatment plants

Estimating the odor emission factors of the grit removal chambers of publicly-owned wastewater treatment plants

Including an Odor Impact Potential in Life Cycle Assessment of waste treatment plants

Odors occupy a leading position among air quality issues of growing concern. Odors can be emitted from different economic sectors, from industrial to agricultural, including waste treatment activities. Although there are different techniques to determine odor emissions, a standardized indicator has not still been defined to include odor impact into methodological tools such as Life Cycle Assessment. In this sense, some proposals can be found in current literature. Considering these approaches, the present work proposes the Odor Impact Potential, an indicator to be used in Life Cycle Assessment or in waste treatment technologies benchmarking. A simple method is reported to calculate the Odor Impact Potential value from different types of data: chemical analysis of odorants or olfactometric determinations. Data obtained in a previous work for an industrial scale anaerobic digestion plant have been used to present an example of application. Additional Odor Impact Potential calculations from other published data (thermal waste treatment plant and wastewater treatment plant) are also included. The aim of Odor Impact Potential is not to replace parameters such as odor emission rates, odor concentration, or odor emission factors but to use those values to calculate the odor-derived impact in Life Cycle Assessment studies.

Assessment of the Indoor Odour Impact in a Naturally Ventilated Room.

Indoor air quality influences people’s lives, potentially affecting their health and comfort. Nowadays, ventilation is the only technique commonly used for regulating indoor air quality. CO2 is the reference species considered in order to calculate the air exchange rates of indoor environments. Indeed, regarding air quality, the presence of pleasant or unpleasant odours can strongly influence the environmental comfort. In this paper, a case study of indoor air quality monitoring is reported. The indoor field tests were conducted measuring both CO2 concentration, using a photoacoustic multi-gas analyzer, and odour trends, using an electronic nose, in order to analyze and compare the information acquired. The indoor air monitoring campaign was run for a period of 20 working days into a university room. The work was focused on the determination of both CO2 and odour emission factors (OEF) emitted by the human activity and on the evaluation of the odour impact in a naturally ventilated room. The results highlighted that an air monitoring and recycling system based only on CO2 concentration and temperature measurements might be insufficient to ensure a good indoor air quality, whereas its performances could be improved by integrating the existing systems with an electronic nose for odour detection.

Evaluation of an Odour Emission Factor (OEF) to estimate odour emissions from landfill surfaces

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 role of bioethanol flueless fireplaces on indoor air quality: Focus on odour emissions

This study concerns flueless fireplaces powered by liquid or gel bioethanol based fuels. These devices have a pleasant aesthetic design and can be used in indoor environments; in particular, they do not need any connection to a stack to evacuate the flue gases.This work evaluates the polluting impact of the mentioned fireplaces, with a special focus on their odour emissions, in order to assess the environmental impact of these items and to provide the European Commission information useful to define the guidelines for a dedicated legislation. For these reasons, a series of experimental tests, structured with well-defined steps, alternating operation (combustion) and shutdown phases, was performed for several fireplaces.The concentration trends of both the main combustion products and by-products as well as the odour were monitored; furthermore, specific odour emission factors (OEFs) were calculated. The combustion pollutants were mainly released during the operation phase, while the most significant odour emissions occurred during shutdown. The average OEFs reached values between 40 and 110 [*100 ouE kJ−1] during the shutdown, but they were below 10 [*100 ouE kJ−1] during the operation periods. It was found that the extent of odour emissions depends crucially on the burner design and geometry of each fireplace; in particular, the air-fuel contact surface is the most relevant parameter.Moreover, this study proved that the electronic nose can be a valid additional instrument in activities aimed at evaluating the indoor air quality, and considering its peculiarities, the idea of using it not only as an odour detector, but also as an integrated device in air ventilation systems for indoor environments, is both interesting and achievable.

Odor Emission Factors from Livestock Production

The aim of this study was to review papers about odor emissions from livestock production published between 1997 and 2013. The study concerned three animal species: poultry, swine, and dairy cattle. The results of the research are presented in different units, making it difficult to compare them. For this purpose, the odor emission factors were converted with respect to 1 LU (livestock unit=500 kg). The calculated mean odor emission factor was greatest for poultry, followed by swine and dairy cattle, but the coefficient of variation for all animal species was high. Such a variability could be caused by weather and microclimate conditions, the housing system, and measurement methods. Therefore, it is reasonable to continue the odor emission research in order to precisely determine the values of odor emission factors. It is also necessary to develop the common unified methods for air sample collecting as well as unified unit of odor emission factor to make odor emission factors more comaparable. It may be useful in establishing any legal regulations on this subject.

The Emission of Odor from LivestockBuildings for Dairy Cattle in Poland

Abstract. The aim of the study was to determine the momentary odor emission factors from two groups of free-stall dairy cattle barns (traditional and modern frame barns) with natural ventilation systems. The odor emission was measured in Poland (Greater Poland) from spring to autumn 2012. The researched six free-stall dairy cattle barns differed also in the type of resting area and manure removal system. The concentrations of odor were measured with the dynamic olfactometry method according to the European Standard EN 13725:2003 procedure. The concentration of odor in the monitored barns ranged from 101 to 825 ou E m -3 thus it characterized high variability. The mean momentary odor emission factors were lower (p≤0.05) for traditional designs barns than for modern frame barns and ranged from 0.04 to 0.061 ou E s -1 kg -1 and 0.127-0.171 ou E s -1 kg -1 , respectively. The housing system (deep litter, shallow litter, cubicles with floor mats or litter) did not influence on odor emission factors within modern frame barns group and also within the group of traditional designs barns (p≤0.05).

Continuous odour measurement from fattening pig units

A study in experimental slatted-system fattening pig units was conducted with the aim of estimating the odour emission factor (in ou s.pig−1), which can subsequently be used in dispersion models to assess the odour annoyance zone. Dynamic olfactometry measurements carried out at different development stages of pigs showed a logical trend of the mean assessed odour emission factor with the pig mass. However, the variation within the same mass class was much larger than variation between classes. Possible causes of such variation were identified as the evolution of ventilation rate during the day and the circadian rhythm of pig. To be able to monitor continuously the daily variation of the odour, an electronic nose was used with suitable regression model calibrated against olfactometric measurements. After appropriate validation check, the electronic nose proved to be convenient, as a complementary tool to dynamic olfactometry, to record the daily variation of the odour emission factor in the pig barn. It was demonstrated that, in the controlled conditions of the experimental pens, the daily variation of the odour emission rate could be mainly attributed to the sole influence of the circadian rhythm of pig. As a consequence, determining a representative odour emission factor in a real case cannot be based on a snapshot odour sampling.

Odor and Odorous Chemical Emissions from Animal Buildings: Part 1. Project Overview, Collection Methods, and Quality Control

Livestock facilities have historically generated public concerns due to their emissions of odorous air and various chemical pollutants. Odor emission factors and identification of principal odorous chemicals are needed to better understand the problem. Applications of odor emission factors include inputs to odor setback models, while chemical emission factors may be compared with regulation thresholds as a means of demonstrating potential health impacts. Acompanion study of the National Air Emissions Monitoring Study (NAEMS) included measurements necessary for establishing odor and chemical emission factors for confined animal feeding operations. This additional investigation was conducted by the University of Minnesota, Iowa State University, West Texas A&M Agri-Life Center, and Purdue University. The objectives were to (1) determine odor emission rates across swine and dairy facilities and seasons using common protocols and standardized olfactometry methods, (2) develop a chemical library of the most significant odorants, and (3)correlate the chemical library with the olfactometry results. This document describes the sampling and quality assurance methods used in the measurement and evaluation of odor and chemical samples collected at two freestall dairy farms, one sow (gestation/farrowing) facility, and one finishing pig site. Odor samples were collected in Tedlar bags and chemical samples were collected in sorbent tubes at barn inlet and exhaust locations using the NAEMS multiple-location gas sampling systems. Quality assurance protocols included interlaboratory comparison tests, which were evaluated to identify variations between olfactometry labs. While differences were observed, the variations among the labs and samples appeared random and the collected odor data were considered reliable at a 0.5% level of statistical significance. Overall, the study took advantage of groundbreaking opportunities to collect and associate simultaneous odor and chemical information from swine and dairy buildings while maintaining accordance with standard methods and comparability across laboratories.

Odor and Odorous Chemical Emissions from Animal Buildings: Part 6. Odor Activity Value

There is a growing concern with air and odor emissions from agricultural facilities. A supplementary research project was conducted to complement the U.S. National Air Emissions Monitoring Study (NAEMS). The overall goal of the project was to establish odor and chemical emission factors for animal feeding operations. The study was conducted over a 17-month period at two freestall dairies, one swine sow farm, and one swine finisher facility. Samples from a representative exhaust airstream at each barn were collected in 10 L Tedlar bags and analyzed by trained human panelists using dynamic triangular forced-choice olfactometry. Samples were simultaneously analyzed for 20 odorous compounds (acetic acid, propanoic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, hexanoic acid, heptanoic acid, guaiacol, phenol, 4-methylphenol, 4-ethylphenol, 2-aminoacetophenone, indole, skatole, dimethyl disulfide, diethyl disulfide, dimethyl trisulfide, hydrogen sulfide, and ammonia). In this article, which is part 6 of a six-part series summarizing results of the project, we investigate the correlations between odor concentrations and odor activity value (OAV), defined as the concentration of a single compound divided by the odor threshold for that compound. The specific objectives were to determine which compounds contributed most to the overall odor emanating from swine and dairy buildings, and develop equations for predicting odor concentration based on compound OAVs. Single-compound odor thresholds (SCOT) were statistically summarized and analyzed, and OAVs were calculated for all compounds. Odor concentrations were regressed against OAV values using multivariate regression techniques. Both swine sites had four common compounds with the highest OAVs (ranked high to low: hydrogen sulfide, 4-methylphenol, butyric acid, isovaleric acid). The dairy sites had these same four compounds in common in the top five, and in addition diethyl disulfide was ranked second at one dairy site, while ammonia was ranked third at the other dairy site. Summed OAVs were not a good predictor of odor concentration (R2 = 0.16 to 0.52), underestimating actual odor concentrations by 2 to 3 times. Based on the OAV and regression analyses, we conclude that hydrogen sulfide, 4-methylphenol, isovaleric acid, ammonia, and diethyl disulfide are the most likely contributors to swine odor, while hydrogen sulfide, 4-methyl phenol, butyric acid, and isovaleric acid are the most likely contributors to dairy odors.

Predicting odour emissions from wastewater treatment plants by means of odour emission factors

In this study, the results of odour concentration measurements on different wastewater treatment plants are presented and used in order to estimate the odour emission factors relevant to single odour sources. An odour emission factor is a representative value that relates the quantity of odour released to the atmosphere to a specific activity index, which in this case was the plant treatment capacity, resulting in an odour emission factor expressed in odour units per cubic metre of treated sewage. The results show that the major odour source of a wastewater treatment plant is represented by the primary sedimentation (with an OEF equal to 1.9 × 10 5 ou E m −3). In general, the highest OEFs are observed in correspondence of the first steps of the wastewater depuration cycle (OEF between 1.1 × 10 4 ou E m −3 and 1.9 × 10 5 ou E m −3) and tend to decrease along the depuration process (OEF between 7.4 × 10 3 ou E m −3 and 4.3 × 10 4 ou E m −3). In general, the OEFs calculated according to this approach represent a model for a rough prediction of odour emissions independently from the specific characteristics of the different plants.