Evaluation of means to measure emissions and air flows through naturally ventilated livestock buildings

• Autor(a) principal: Mendes, Luciano Barreto
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/786
• topic: Bovino de leite - Instalações; Frango de corte - Instalações; Ventilação; Gases - Análise; Milk and veal - Facilities; Broiler - Facilities; Ventilation; Gases - Analysis; CNPQ::CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA

This thesis was prepared as an attempt to cover a number of questions and concerns regarding the current available means to measure emissions and air flows from naturally ventilated (NV) livestock buildings. Five were the main objectives that led to the preparation of this thesis: (1) to assess the operation performance of a low cost carbon dioxide (CO2) measuring device and to compare it to two other standard methods; (2) to evaluate the distribution of mixing ratios of the pollutant ammonia (NH3) and the tracer gases sulfur-hexafluoride (SF6) and CO2 in a NV dairy cow barn; (3) to develop a CFD model of a NV dairy cow barn implemented with the CIGR CO2 production model; (4) to develop and test a protocol for measuring NH3 emissions from a Brazilian NV broiler house; and (5) to calculate NH3 emission factors from a Brazilian NV and a mechanically ventilated (MV) broiler barns. Five papers were prepared to answer the five objectives of this thesis, which include a variety of factors and implications related to a NV dairy cow barn in the Netherlands and a NV broiler barn in Brazil. The first paper dealt with the comparison between two CO2 concentration measuring devices that are commonly used for emission studies in MV barns with one low cost sensor that is new to research purposes and might be more suitable for NV livestock buildings. In the second paper, we compared mixing ratios calculated with NH3 and two different tracers, the CO2 which is naturally produced in livestock houses and the artificially injected SF6 with the aim of identifying the region within the barn ventilated airspace where mixing ratios are approximately constant, from which representative estimates of emission rates through the tracer gas method can be made. In paper number three, a Computational Fluid Dynamics (CFD) model of a NV dairy cow barn was developed and implemented with the CIGR CO2 production equations in order to reveal the flow patterns of air and CO2 within the ventilated airspace. The model was validated with CO2 concentration data actually measured at multiple points within the barn. The fourth paper was about finding a more adequate algorithm for determining flow rates across a NV broiler barn in Brazil. The tested sampling strategies combined two different sampling schemes for gaseous concentrations and two different strategies to 12xi predict CO2 production from the birds. The fifth and last paper was a follow up of paper number four, and dealt with calculation of actual NH3 emission factors ( f NH ) 3 of a NV and a MV broiler barns in Brazil. The method used to estimate the emission factors in both barns was based on a tracer gas, using the CO2 naturally produced by the birds as the tracer. The calculated f NH were then compared to those found in the 3 literature for Brazilian conditions and those found in other parts of the world. Overall, this thesis proves that despite the complications related to monitoring air and gaseous pollutant flows through NV buildings, emission factors can be obtained which are comparable to those of MV buildings. In general, the number of points in which gaseous concentrations are being monitored within the barn ventilated airspace with properly calibrated devices is more important than using highly accurate and expensive measurement methods. When the tracer gas method is to be used, focus should be given to accurate determination of the tracer injection rate or rate of production of CO2. It is important that the mixing ratio between pollutant and tracer gases be determined in multiple points outside the animal occupied zone, but above it.