V. A. Dodd

The influence of diet crude protein level on odour and ammonia emissions from finishing pig houses

Feed trials were carried out to assess the influence of crude protein content in finishing pig diets on odour and ammonia emissions. Eight pigs (4 boars and 4 gilts), average initial weight 70.8 kg (s.e. 3.167) were housed in two pens that were isolated from the rest of a pig house at University College Dublin Research Farm, Newcastle, Dublin, Ireland. Four diets containing 130, 160, 190 and 220 g x kg(-1) crude protein were fed during six four-week feeding periods (one treatment per room). The first week of the feeding periods served to allow odour build up in the pens and as a dietary adjustment period. The pens had partially slatted floors that were cleaned and had all the manure removed after each four-week period. Odour and ammonia concentrations were measured on days 9, 14, 16, 21 and 23 of each trial period. Odour samples were collected in Nalophan bags and analysed for odour concentration using an ECOMA Yes/No olfactometer. The odour threshold concentration was calculated according to the response of the olfactometry panel members and was displayed in Ou(E)m(-3), which referred to the physiological response from the panel equivalent to that elicited by 40 ppbv(-1) n-butanol evaporated in 1 m(3) of neutral gas. Ammonia concentrations in the ventilation air were measured using Dräger tubes. The odour emission rates per animal for the 130, 160, 190 and 220 g x kg(-1) crude protein diets were 12.1, 13.2, 19.6 and 17.6 Ou(E)s(-1)animal(-1), respectively (P<0.01). The odour emission rate per livestock unit (500 kg) for the 130, 160, 190 and 220 g x kg(-1) crude protein diets were 77.6, 80.0, 115.8 and 102.9 Ou(E)s(-1)LU(-1), respectively (P<0.01). The ammonia emission rates per animal for the 130, 160, 190 and 220 g x kg(-1) crude protein diets were 3.11, 3.89, 5.89 and 8.27 g x d(-1)animal(-1), respectively (P<or=0.001). There was no significant difference in the average daily intake and the average daily gain for the four diets (P>0.05). Manipulation of dietary crude protein levels would appear to offer a low cost alternative, in relation to end-of-pipe treatments, for the abatement of odour and ammonia emissions from finishing pig houses.

Biofiltration of n-butyric acid for the control of odour

Odour control from pig production facilities is a significant concern due to increased public awareness and the development of more stringent legislation to control production. Although many technologies exist, biofiltration is still the most attractive due to its low maintenance and operating costs. One of the key odour components, n-butyric acid, was selected for a laboratory scale biofilter study. It was examined as a sole carbon substrate in order to investigate the effectiveness of biofiltration in reducing n-butyric acid concentration under different operating conditions using a moist enriched woodchip medium. Three superficial gas velocities; 38.2, 76.4, and 114.6 m x h(-1) were tested for n-butyric acid concentrations ranging from 0.13 to 3.1 g [n-butyric acid] m(-3) [air]. For superficial gas velocities 38.2, 76.4, and 114.6 m x h(-1), maximum elimination capacities (100% removal) of 148, 113 and 34.4 g x m(3) x h(-1), respectively, were achieved. Upon investigation of effective bed height, true elimination capacities (100% removal) of 230, 233 and 103 g x m(-3) x h(-1), respectively, were achieved at these superficial gas velocities. Averaged pressure drops for superficial gas velocities 38.2, 76.4, and 114.6 m x h(-1) were 30, 78 and 120 Pa, respectively. It was concluded that biofiltration is a viable technology for the removal of n-butyric acid from waste exhaust air, but near 100% removal efficiency is required due to the low odour detection threshold for this gaseous compound.

Evaluation of the odour reduction potential of alternative cover materials at a commercial landfill

The availability of virgin soils and traditional landfill covers are not only costly and increasingly becoming scarce, but they also reduce the storage capacity of landfill. The problem can be overcome by the utilisation of certain suitable waste streams as alternative landfill covers. The objective of this study was to assess the suitability of Construction & Demolition fines (C&D), Commercial & Industrial fines (C&I) and woodchip (WC) as potential landfill cover materials in terms of odour control. Background odour analysis was conducted to determine if any residual odour was emitted from the cover types. It was deemed negligible for the three materials. The odour reduction performance of each of the materials was also examined on an area of an active landfill site. A range of intermediate cover compositions were also studied to assess their performance. Odour emissions were sampled using a Jiang hood and analysed. Results indicate that the 200 mm deep combination layer of C&D and wood chip used on-site is adequate for odour abatement. The application of daily cover was found to result in effective reduction allowing for the background odour of woodchip.

Odour and ammonia emissions from pig and poultry units

Odour and ammonia emission rates were measured at three pig units, three broiler units and one layer unit. The ventilation rates in the pig and poultry houses were calculated using readings from an anemometer and a CO2 sensor. Ammonia concentrations were measured using Draeger tubes and an electrochemical sensor. Air samples were collected in exhaust ventilation air on site and odour concentrations in the samples were determined using an ECOMA T07 olfactometer. Mean odour and ammonia emission rates for finishing pigs ranged from 6.0-10.7 OuE s-1 pig-1 and 8.4-10.0 g day-1 pig-1, respectively. The minimum odour emission rate in pig housing was 4.6 OuE s-1 pig-1 for 1st stage weaners and the maximum was 66.4 OuE s-1 pig-1 for farrowing houses. Mean odour and ammonia emission rates for broilers ranged from 0.45-0.55 OuE s-1 bird-1 and 0.14-0.42 g day-1 bird-1, respectively. The layer unit had a low odour concentration but a similar odour emission rate of 0.43 OuE s-1 bird-1. Most of the emission rates were comparable to those found by other researchers. However, there is a lack of unanimity in the literature and a scarcity of published data, particularly for poultry units. The variability in the figures highlights the need for individual site assessment. The emission rates are useful as inputs to atmospheric dispersion models to determine appropriate ‘setback’ distances. Further research is being carried out on other pig and poultry units to assess the influence of factors such as building design, manure management, unit operation and diet.

Evaluation of ISC3 and CALPUFF Atmospheric Dispersion Models for Odor Nuisance Prediction

This paper presents an evaluation of a plume model (ISC3) and an advanced puff model (CALPUFF) for the prediction of odor concentrations at a commercial pig unit. Key parameters such as odor emission rate and meteorological conditions were measured at source. Downwind odor intensity was assessed by field panelists during 10-minute periods on three sampling days and converted to mean concentrations by equations developed from laboratory analysis of source odor samples. Emission characteristics and meteorological data were inputted to both ISC3 and the screening mode of CALPUFF. Both models produced similar predicted odor concentrations. The average predicted to measured mean concentration ratio on the sampling days varied from 1.40 to 9.37. Over 80% of the predictions were greater than the corresponding measured values, thus indicating that both models produce conservative estimates of downwind odor concentration.