Ammonia emissions from a dairy housing and wastewater treatment plant quantified with an inverse dispersion method accounting for deposition loss

Ammonia (NH3) emissions negatively impact air, soil, and water quality, hence human health and biodiversity. Significant emissions, including the largest sources, originate from single or multiple structures, such as livestock facilities and wastewater treatment plants (WWTPs). The inverse dispersion method (IDM) is effective in measuring total emissions from such sources, although depositional loss between the source and point of measurement is often not accounted for. We applied IDM with a deposition correction to determine total emissions from a representative dairy housing and WWTP during several months in autumn and winter in Switzerland. Total emissions were 1.19 ± 0.48 and 2.27 ± 1.53 kg NH3 d-1 for the dairy housing and WWTP, respectively, which compared well with literature values, despite the paucity of WWTP data. A concurrent comparison with an inhouse tracer ratio method at the dairy housing indicated an offset of the IDM emissions by < 20%. Diurnal emission patterns were evident at both sites mostly driven by changes in air temperature with potential lag effects such as following sludge agitation. Modeled deposition corrections to adjust the concentration loss detected at the measurement point with the associated footprint were 22-28% of the total emissions and the cumulative fraction of deposition to emission modeled with distance from the source was between 7% and 12% for the measurement distances (60-150 m). Although estimates of depositional loss were plausible, the approach is still connected with substantial uncertainty, which calls for future validation measurements. Longer measurement periods encompassing more management activities and environmental conditions are required to assess predictor variable importance on emission dynamics. Combined, IDM with deposition correction will allow the determination of emission factors at reduced efforts and costs, thereby supporting the development and assessment of emission reducing methods and expand the data availability for emission inventories.Implications: Ammonia emissions must be measured to determine emission factors and reporting national inventories. Measurements from structures like farms and industrial plants are complex due to the many different emitting surfaces and the building configuration leading to a poor data availability. Micrometeorological methods provide high resolution emission data from the entire structure, but suffer from uncertainties, as the instruments must be placed at a distance from the structure resulting in a greater loss of the emitted ammonia via dry deposition before it reaches the measurement. This study constrains such emission measurements from a dairy housing and wastewater treatment plant by applying a simple correction to account for the deposition loss and compares the results to other methods.

Effect of diets with different crude protein levels on ammonia and greenhouse gas emissions from a naturally ventilated dairy housing

Less crude protein (CP) in the diet can reduce nitrogen excretion of dairy cattle and lower their ammonia (NH3) and nitrous oxide (N2O) formation potential. The diet composition might also affect emissions of methane (CH4) and carbon dioxide (CO2). However, previous studies did not investigate the effect of diets with different CP levels that are customary practice in Switzerland on NH3 and greenhouse gas emissions on a practical scale. In a case-control approach, we quantified the emissions (NH3, N2O, CH4, CO2) in two separate but identical compartments of a naturally ventilated cubicle housing for lactating dairy cows over six days by using a tracer ratio method. Cows in one compartment received a diet with 116 g CP per kilogram dry matter (DM), in the other compartment with 166 g CP kg-1 DM. Subsequently, diets were switched for a second 6-day measurement phase. The results showed that the diet, aside from outside temperature and wind speed in the housing, was driving NH3 and N2O emissions. NH3 and N2O emission reduction per livestock unit (LU) was on average 46 % and almost 20 %, respectively, for the diet with low CP level compared to the higher CP level. In addition, strong relationships were observed between the CP content of the diet, N excretion in the urine and the milk urea content. An increased temperature or wind speed led to a clear increase in NH3 emissions. Differences in CH4 and CO2 emissions per LU indicated a significant influence of the diet, which cannot be attributed to the CP content. Our herd-level study demonstrated that a significant reduction in NH3 and N2O emissions related to LU, energy-corrected milk as well as DM intake can be achieved by lowering the CP content in the diet.

Effects of Acacia mearnsii added to silages differing in nutrient composition and condensed tannins on ruminal and manure-derived methane emissions of dairy cows

This study investigated the effects of acacia (extract of Acacia mearnsii) and sainfoin (Onobrychis viciifolia) as condensed tannin (CT)-rich sources on ruminal and manure methane (CH4) emissions in comparison with non-CT silages characterized by different contents of the cell wall and water-soluble carbohydrates. In a 3 × 6 incomplete Latin square design, 30 Holstein cows (63 ± 23 d in milk; mean ± SD; 33.8 ± 7.6 kg of milk per day, body weight 642 ± 81 kg) were provided with ad libitum access to 1 of 6 total mixed rations comprising 790 g of silage and 210 g of concentrate per kilogram of dry matter (DM). The silages were either rich in sainfoin [neutral detergent fiber (NDF): 349 g/kg of DM], perennial ryegrass (NDF: 420 g/kg of DM), or red clover (NDF: 357 g/kg of DM). Each silage was supplemented with 20 g/kg (of total diet DM) of acacia or straw meal. Feed intake and milk yield were recorded daily. Milk composition and ruminal fluid characteristics and microbiota were analyzed. The individual ruminal CH4 production was determined using the GreenFeed system, and CH4 emissions from the manure of cows fed the same diets were measured in a parallel experiment over 30 d at 25°C using a dynamic flux chamber. The CT sources did not reduce CH4 yield or emission intensity. Acacia reduced milk production (from 26.3 to 23.2 kg/d) and DM intake (from 19.7 to 16.7 kg/d) when supplemented with ryegrass, and both CT sources reduced the milk protein content and yield. Acacia supplementation and ryegrass silage reduced the ruminal acetate:propionate ratio. Furthermore, during acacia treatment, the abundance of Methanobrevibacter archaea tended to be lower and that of Thermoplasmata was higher. Acacia reduced the CH4 emissions from manure for the ryegrass group by 17% but not for the sainfoin and clover groups. Feeding sainfoin silage resulted in the lowest manure-derived CH4 emissions (-47% compared with ryegrass). In conclusion, acacia reduced ruminal CH4 production by 10%, but not emission intensity, and the mitigation effect of sainfoin depended on the silage to which it was compared. Because mitigation was partially associated with animal productivity losses, careful evaluation is required before the implementation of tanniferous feeds in farm practice.

Occurrence and Fate of Natural Estrogens in Swiss Cattle and Pig Slurry

Natural estrogens act as endocrine disruptors. However, the fate of livestock farming derived natural estrogens (17α-estradiol, 17β-estradiol, estrone, and estriol) in slurry is not well understood. In this study, we assessed the effects of on farm-storage on natural estrogen concentrations in slurry. Furthermore, we monitored pig and cattle slurry pits from major agricultural areas in Switzerland and determined natural estrogen concentrations therein. They were relatively stable over time, and mean concentrations ranged from 138 to 861 and 54 to 244 ng/L for cattle and pig slurries, respectively. 17α-Estradiol and estriol were the most prevalent estrogens in cattle and pig slurries, respectively. Based on livestock numbers, agricultural area, and estrogen concentrations in slurry, the estimated annual load of total natural estrogens applied on agricultural area amounted to 36 mg/ha. Our results indicate that slurry application is a relevant source of natural estrogens in the environment.

Odour impact from farms with animal husbandry and biogas facilities

Agricultural biogas facilities are usually combined with animal husbandry. Their siting near residential areas can lead to odour complaints by residents. The aim of this study was to identify relevant odour sources, to record odour impact, and to determine the main variables influencing odour impact. Therefore, a combined approach was designed to account for individual odour sources as well as the farms as a whole. On eight farms with cattle husbandry and biogas facilities, two of which kept pigs and poultry, the odour-relevant area sources ranged between 475 and 1810 m². Solid manure from poultry, cattle and horses as well as grass cuttings, vegetable peelings, liquid-silage effluent and fermentation residues figured among the odour-intensive sources, in addition to biogas. Odour-plume inspections were performed at various distances from the farm, and assessors determined their odour perception and -intensities. The odour intensity in the downwind plume axis was explainable in a linear mixed-effects model by distance (p < 0.001), emitting surface area (p = 0.002) and wind speed (p = 0.018). As distance increased, odour intensity decreased by a factor of two per 50 m. Higher odour intensities resulted from larger surface areas in the animal enclosure, substrate storage, or especially odour-relevant sources. A mixture of odours was frequently perceived in the odour plume. If biogas escaped, an increase in odour impact was recognisable (p = 0.021). Biogas leakage should be avoided with a sufficiently large storage capacity, process optimisation, and regular servicing. In summary, animal husbandry and biogas facilities are to be viewed as an entire plant in terms of downwind odour perception. In planning processes for biogas facilities with animal husbandry, great care in the choice of site is called for, as are structural-technical and organisational measures for abatement.