Salvador Calvet

Airborne particulate matter from livestock production systems: a review of an air pollution problem.

Livestock housing is an important source of emissions of particulate matter (PM). High concentrations of PM can threaten the environment, as well as the health and welfare of humans and animals. Particulate matter in livestock houses is mainly coarse, primary in origin, and organic; it can adsorb and contain gases, odorous compounds, and micro-organisms, which can enhance its biological effect. Levels of PM in livestock houses are high, influenced by kind of housing and feeding, animal type, and environmental factors. Improved knowledge on particle morphology, primarily size, composition, levels, and the factors influencing these can be useful to identify and quantify sources of PM more accurately, to evaluate their effects, and to propose adequate abatement strategies in livestock houses. This paper reviews the state-of-the-art of PM in and from livestock production systems. Future research to characterize and control PM in livestock houses is discussed.

Characterization of gas emissions from a Mediterranean broiler farm

Gas emissions from broiler production have been the subject of intensive research. However, little experimental information exists for farms under the particular management and environmental conditions of the European Mediterranean area. In this study, ammonia, carbon dioxide, methane, and nitrous oxide concentrations and emissions were measured in a commercial broiler farm located in Spain. Gas concentrations were measured using a photoacoustic gas monitor, whereas the ventilation flow was evaluated by controlling the operation status of each fan. Two rearing periods were studied, one in summer and one in winter. All gas emissions increased with bird age. Ammonia emission rates averaged 19.7 and 18.1 mg/h per bird in the summer and winter, respectively, and increased with indoor temperature (r(2) = 0.51 in summer; r(2) = 0.42 in winter). Average CO(2) emission rates were 3.84 and 4.06 g/h per bird, CH(4) emission was 0.44 and 1.87 mg/h per bird, and N(2)O emission was 1.74 and 2.13 mg/h per bird in summer and winter, respectively. A sinusoidal daily variation pattern was observed in all emissions except for CH(4). These patterns were characterized in terms of time of maximum emission and amplitude of the daily variation.

The influence of broiler activity, growth rate, and litter on carbon dioxide balances for the determination of ventilation flow rates in broiler production

Carbon dioxide balances are useful in determining ventilation rates in livestock buildings. These balances need an accurate estimation of the CO(2) produced by animals and their litter to determine the ventilation flows. To estimate the daily variation in ventilation flow, it is necessary to precisely know the daily variation pattern of CO(2) production, which mainly depends on animal activity. The objective of this study was to explore the applicability of CO(2) balances for determining ventilation flows in broiler buildings. More specifically, this work aimed to quantify the amount of CO(2) produced by the litter, as well as the amount of CO(2) produced by the broilers, as a function of productive parameters, and to analyze the influence of broiler activity on CO(2) emissions. Gas concentrations and ventilation flows were simultaneously measured in 3 trials, with 1 under experimental conditions and the other 2 in a commercial broiler farm. In the experimental assay, broiler activity was also determined. At the end of the experimental trial, on the day after the removal of the broilers, the litter accounted for 20% of the total CO(2) produced, and the broilers produced 3.71 L/h of CO(2) per kg of metabolic weight. On the commercial farm, CO(2) production was the same for the 2 cycles (2.60 L/h per kg of metabolic weight, P > 0.05). However, substantial differences were found between CO(2) and broiler activity patterns after changes in light status. A regression model was used to explain these differences (R(2) = 0.52). Carbon dioxide increased with bird activity, being on average 3.02 L/h per kg of metabolic weight for inactive birds and 4.73 L/h per kg of metabolic weight when bird activity was highest. Overall, CO(2) balances are robust tools for determining the daily average ventilation flows in broiler farms. These balances could also be applied at more frequent intervals, but in this case, particular care is necessary after light status changes because of discrepancy between animal activity and CO(2) production.

Suitability Evaluation of Multipoint Simultaneous CO2 Sampling Wireless Sensors for Livestock Buildings

The environment in livestock buildings must be controlled to ensure the health and welfare of both workers and animals, as well as to restrict the emission of pollutants to the atmosphere. Among the pollutants generated inside these premises, carbon dioxide (CO2) is of great interest in terms of animal welfare and ventilation control. The use of inexpensive sensors means that complete systems can be designed with a number of sensors located around the building. This paper describes a study of the suitability of multipoint simultaneous CO2 sensors operating in a wireless sensor network, which was found to operate satisfactorily under laboratory conditions and was found to be the best alternative for these applications. The sensors showed a highly linear response to CO2 concentrations, ranging from 500 to 5000 ppm. However, individual sensor response was found to differ, which made it necessary to calibrate each one separately. Sensor precision ranged between 80 and 110 ppm CO2, and sensor response to register a 95% change in concentration was estimated at around 5 min. These features mean this type of sensor network can be used to monitor animal welfare and also for environmental control in poorly ventilated livestock premises. According to the tests conducted in this study, a temporal drift may occur and therefore a regular calibration of sensors would be needed.

Evaluation of the NH3 Removal Efficiency of an Acid Packed Bed Scrubber Using Two Methods: A Case Study in a Pig Facility

The use of air cleaning systems to reduce ammonia emissions from animal houses is increasing. These systems are normally used in order to comply with local or national regulations of ammonia emission. Therefore, accurate determination of the proportion of ammonia being removed by these systems is crucial. There are two main methods available to measure ammonia removal efficiency of scrubbers: air balance (based on the measurement of ammonia concentrations in air) and combined water-air balance (in which it is also necessary to determine the amount of nitrogen recovered in the liquid phase). The first method is simpler to establish, while the second method might provide deeper information about the processes occurring. The main aim of this work was to assess, in terms of the variability of the results, the use of these two methods to evaluate the efficiency of an acid packed bed scrubber on a pig farm. An acid packed bed scrubber (70% NH3 removal) was monitored during ten complete 24 h cycles for ammonia concentrations, airflow rates, and nitrogen accumulation in the acid solution basin. The average efficiency calculated using the air balance method was 71% (±4%), close to the design value of 70%, while the average efficiency when using the combined water-air balance method was 255% (±53%). The accumulation and precipitation of ammonium salts in the packing material seem to be the main cause of the high variability and inaccuracy of the combined water-air balance method observed for this type of scrubber. According to these results, it is recommended to use the air balance method when determining the ammonia removal efficiency for acid packed bed scrubbers similar to the one studied here. According to the variability of the results observed in this work, at least 24 measurement days are needed in order to keep the relative error below 5% when using the air balance method to determine the ammonia removal efficiency of an acid packed bed scrubber.

Low frequency aeration of pig slurry affects slurry characteristics and emissions of greenhouse gases and ammonia

Low frequency aeration of slurries may reduce ammonia (NH3) and methane (CH4) emissions without increasing nitrous oxide (N2O) emissions. The aim of this study was to quantify this potential reduction and to establish the underlying mechanisms. A batch experiment was designed with 6 tanks with 1 m3 of pig slurry each. After an initial phase of 7 days when none of the tanks were aerated, a second phase of 4 weeks subjected three of the tanks to aeration (2 min every 6 h, airflow 10 m3 h−1), whereas the other three tanks remained as a control. A final phase of 9 days was established with no aeration in any tank. Emissions of NH3, CH4, carbon dioxide (CO2) and N2O were measured. In the initial phase no differences in emissions were detected, but during the second phase aeration increased NH3 emissions by 20% with respect to the controls (8.48 vs. 7.07 g m−3 [slurry] d−1, P < 0.05). A higher pH was found in the aerated tanks at the end of this phase (7.7 vs. 7.0 in the aerated and control tanks, respectively, P < 0.05). CH4 emissions were 40% lower in the aerated tanks (2.04 vs. 3.39 g m−3 [slurry] d−1, P < 0.05). These differences in NH3 and CH4 emissions remained after the aeration phase had finished. No effect was detected for CO2, and no relevant N2O emissions were detected during the experiment. Our results demonstrate that low frequency aeration of stored pig slurry increases slurry pH and increases NH3 emissions.

Implications of increasing ventilation rates of broiler farms to fulfill European welfare regulations on gas concentrations

Ammonia and carbon dioxide concentrations are limited in the EU when rearing density exceeds 33 kg/m2. Threshold concentrations (20 and 3,000 ppm for ammonia and carbon dioxide respectively), have been reported to be higher in literature. One of the simplest ways to reduce these concentrations through increasing ventilation rates, although this technique may lead to higher energy consumption due to ventilation and heating needs. The aim of this paper is to evaluate this extra energetic cost in a practical case in a broiler house. To this aim, a broiler house (24,000 places) located in a mild Mediterranean area (Villarreal, Castellon, Spain), was monitored for gas concentrations and ventilation rates during a whole winter cycle. A sensible heat balance was developed to determine heat needs during the cycle. Later, gas concentrations during the cycle were evaluated and when they were higher than the established limits, the extra ventilation rates needed to reduce these concentrations were calculated. The implication on heat consumption of this extra ventilation was also determined using a sensible heat balance. On average, ventilation rated had to be increased 9.87% for the whole rearing cycle. This extra ventilation implied an over energy consumption of 28.61% considering the whole cycle. Ammonia was the main contributor to these extra ventilation needs since carbon dioxide concentrations were found to be high only during the first days of the cycle. It should be considered that the interpretation of some aspects of the regulation may lead to strong modifications of these extra costs.

Estimation of Emission Uncertainty from a Broiler Building Using Numerical Methods

The report of an emission rate must include an estimation of the measurement error in the results. In this work the uncertainty in the ammonia emission rates was evaluated using numerical methods (Monte Carlo methods), which constitute a robust methodology to propagate uncertainties. The main objectives were to define properly the influencing variables, to study the contribution of these variables, and to account for the existing dependence between variables, particularly gas concentrations and ventilation flows. Ammonia emissions and ventilation flows were simultaneously measured for one growing period in a commercial broiler facility. Emission rates and their uncertainties were calculated for days 30 and 31 of the growing cycle. Ventilation flow uncertainty was estimated from a previous study, whereas uncertainty in gas concentrations was originated on the instrument calibration and the sampling on the farm, and was specifically obtained for this study. Ammonia emission rates ranged from 18.58 to 76.80 mg per animal and hour. The gas concentration error depended on the measured value, and was characterized for the measurement system used in this study. The correlation coefficient between gas concentrations difference and ventilation rate over a growing cycle was -0.62. The contribution of gas concentration to the overall emission rate uncertainty was 63%, whereas the ventilation flow contributed by 37%. Finally, if correlations were considered, the emission rate uncertainty decreased. However, this correlation must not be included in the uncertainty if the errors of gas concentration and ventilation flows are independent, despite both variables are correlated by cause and effect.

Measuring ventilation using carbon dioxide balances: evolution of CO2 production from litter in two broiler cycles.

The carbon dioxide (CO2) balance used to determine ventilation rates needs accurate emission values from animals and their manure. The objective of this work was to quantify the amount and evolution of CO2 produced by broiler litter in two 42-day growing cycles, and its contribution to total CO2 emission in the farm. The effect of litter aeration on CO2 production was also investigated. In each studied growing cycle, three groups of 800 male broilers were kept in three 13m x 6m broiler rooms using new wood shavings as bedding material. In two of them, the litter was aerated weekly from day 19 to the end of the growing period (treatment A) with a broiler litter mixer and the other remained as control (treatment C). Litter properties were analyzed weekly for dry matter, ash, nitrogen content and pH. The CO2 concentrations and emissions of each room were continuously monitored. Emissions from the litter were quantified on days 14, 21, 28, 35 and 42 of the growing cycle, using two 0.15 m2 static chambers. CO2 emission from litter was negligible from the beginning of the cycle until day 28. The maximum emission was found at day 42, being on average 7.97 ± 0.32 g CO2/m2/h (average ± S.E.) for C and 9.09 ± 0.23 CO2/m2/h for A. CO2 emissions from litter were affected by litter treatment and animal age. The litter CO2 emissions were not constant in absolute or relative terms during broiler growing cycle, and depend on litter properties, particularly dry matter content. At the end of the cycle, litter contributed to the total CO2 emission from 8 to 16%.

Determining daily average concentrations of ammonia in livestock buildings using a photoacoustic monitor and acid wet traps

Measuring ammonia concentrations accurately is a need for environmental and welfare purposes in livestock production. Several techniques, based on different technologies and time basis, have been developed to determine these concentrations. These techniques can be classified according to a wide range of parameters, but one of the main ones is time resolution. High time resolution techniques provide high frequency measurements, generally at high cost, while low time resolution measurements give normally daily average concentrations, but at a lower cost and with high robustness. In this paper, two ammonia concentrations measurement techniques were compared: a photoacoustic monitor and wet traps (impingers). Measurements were developed during two winter cycles in three experimental broilers houses. 70 daily average values for ammonia concentrations were obtained using both techniques. According to the results, ammonia concentrations were not statistically different, on average terms. Nevertheless, differences between techniques were found when considering only low concentrations (< 2 mg/m3). For higher concentrations, results were similar between techniques. Further research is needed in order to confirm these results.