T.H. Misselbrook

Ammonia emission factors for UK agriculture

Ammonia (NH3) emission inventories are required for modelling atmospheric NH3 transport and estimating downwind deposition. A recent inventory for UK agriculture, estimating emission as 197 kt NH3–N yr−1, was constructed using 1993 statistical and census data for the UK. This paper describes the derivation of the UK-based emission factors used in the calculation of that emission for a range of livestock classes, farm practices and fertiliser applications to agricultural land. Some emission factors have been updated where more recent information has become available. Some of the largest emission factors derived for each farming practice include 16.9 g NH3–N dairy cow−1 d−1 for grazing, 148.8 g NH3–N liveweight unit−1 yr−1 for housed broilers and 4.8 g NH3–N m−2 d−1 for storage of solid pig and poultry waste as manure heaps. Emissions for land spreading of all livestock waste were 59% of the total ammoniacal nitrogen (TAN) applied as a high dry matter content slurry and 76% of TAN applied as farm yard manure. An updated estimate of emission from UK agriculture, using updated emission factors together with 1997 statistical and census data, is presented, giving a total of 226 kt NH3–N per year.

Effect of turning regime and seasonal weather conditions on nitrogen and phosphorus losses during aerobic composting of cattle manure

Cattle manure from stock bedded on straw was aerobically composted under ambient conditions, turning with either a tractor-mounted front-end loader or a rear discharge manure spreader. Three composting experiments, each of approximately four months duration, were conducted to investigate the effect of turning regime and seasonal weather conditions on nitrogen and phosphorus losses during aerobic composting of cattle manure. Manure stacks of 12-15 m(3) initial volume were constructed in separate 5 x 5 m concrete compartments. Experiment 1 (January-April 1999) compared manure heaps turned once (T1) or three times (T3) using a front-end loader with an unturned static (S) control manure stack. Experiment 2 (June-September 1999) compared the same treatments as Experiment 1. Experiment 3 (September-December 1999) compared T1 and T3 turning regimes using a front end loader with turning by a rear-discharge spreader (TR1 and TR1T2) for more effective aeration of the manure. Turning took place at 6 weeks for the one turn treatments, and after 2, 6 and 10 weeks for the three turn treatments. Leachate losses were dominated by NH(4)-N during the first three weeks of composting, after which time NH4-N and NO3-N concentrations in leachates were approximately the same, in the range 0-20 mg N l(-1). The concentrations of both NH4-N and NO3-N in leachate were higher after turning. Molybdate-reactive P concentrations in leachate tended not to be significantly influenced by turning regime. Gaseous losses of NH3 and N2O rose quickly during the initial phases of composting, peaking at 152 g N t(-1) d(-1) for the T3 treatment. Mean NH3 emission rate (25-252 g N t(-1) d(-1)) for the first two weeks of Experiment 2 conducted during the period June-September were an order of magnitude greater (1-10 g N t(-1) d(-1)) than Experiment 3, conducted during the colder, wetter autumn period (September-December). Nitrous oxide emission rates ranged between 1-14 g N t(-1) d(-1) and showed little influence of turning regime. Total N and P concentrations in turned (T) and static (S) manure were elevated at the end of all experiments, due to loss of dry matter. Mean total N losses were 30.4% (T1) and 36.8% (T3) and total P losses 28.2% (T1) and 27.4% (T3).

Algorithms Determining Ammonia Emission from Buildings Housing Cattle and Pigs and from Manure Stores

Livestock excreta and manure stored in housing, in manure stores, in beef feedlots, or cattle hardstandings are the most important sources of ammonia (NH3) in the atmosphere. There is a need to quantify the emission, to assess the effect of emission on NH3 and ammonium (NH4+) deposition to ecosystems and on the health risks posed by NH4+-based particles in the air. To obtain a reliable estimate of the emission from these sources, the processes involved in the transfer of NH3 from the manure to the free atmosphere have to be described precisely. A detailed knowledge of the processes of NH3 transfer from the manure and transport to the free atmosphere will contribute to development of techniques and housing designs that will contribute to the reduction of NH3 emission to the atmosphere. For this reason, this review presents the processes and algorithms involved in NH3 emission from livestock manure in livestock buildings and manure stores for pigs and cattle. Emission from poultry buildings and following land application of manure, although significant sources of NH3, have been reported in earlier reviews and are not included here. A clear description of the features that contribute to the total NH3 emission from buildings will include information on stock class, diet and excreta composition, the distribution of emitting surfaces and knowledge of their mass transfer characteristics in relation to the building as a whole, as well as environmental variables. Other relevant information includes the quantity and composition of excreta produced by different classes of livestock and the influence of feeding regime; the influence of environmental variables on the production of NH3 from excreta; how excreta is distributed and managed in livestock buildings; and factors that affect mass transfer of NH3 in the building to the atmosphere outside. A major factor is the pH of the manure. There is a great need for algorithms that can predict pH as affected by feeding and management. This chapter brings together published estimates of NH3 emissions and abatement techniques, and relates these to the factors listed above (excreta, NH3 production, building, and mass transfer).

Towards a climate-dependent paradigm of ammonia emission and deposition

Existing descriptions of bi-directional ammonia (NH3) land–atmosphere exchange incorporate temperature and moisture controls, and are beginning to be used in regional chemical transport models. However, such models have typically applied simpler emission factors to upscale the main NH3 emission terms. While this approach has successfully simulated the main spatial patterns on local to global scales, it fails to address the environment- and climate-dependence of emissions. To handle these issues, we outline the basis for a new modelling paradigm where both NH3 emissions and deposition are calculated online according to diurnal, seasonal and spatial differences in meteorology. We show how measurements reveal a strong, but complex pattern of climatic dependence, which is increasingly being characterized using ground-based NH3 monitoring and satellite observations, while advances in process-based modelling are illustrated for agricultural and natural sources, including a global application for seabird colonies. A future architecture for NH3 emission–deposition modelling is proposed that integrates the spatio-temporal interactions, and provides the necessary foundation to assess the consequences of climate change. Based on available measurements, a first empirical estimate suggests that 5°C warming would increase emissions by 42 per cent (28–67%). Together with increased anthropogenic activity, global NH3 emissions may increase from 65 (45–85) Tg N in 2008 to reach 132 (89–179) Tg by 2100.

Odour and ammonia emissions following the spreading of aerobically-treated pig slurry on grassland

Anaerobically digested and untreated pig slurries were spread on grassland plots and measurements of odour and ammonia emissions made using a systems of small wind tunnels. Digestion reduced total solids (TS), total nitrogen (TN) and volatile fatty acid (VFA) content of pig slurry and increased pH value. Odour emission during the first 6 h following application was reducd by between 70–80%. Odour intensity was also reduced, but odour offensiveness when measured at the same intensity was unchanged. Digestion had no significant effect on the ammonia volatilization from pig slurry following application to grassland.

A farm-scale study on the use of clinoptilolite zeolite and De-Odorase® for reducing odour and ammonia emissions from broiler houses

Intensive poultry farms are frequently the subject of odour complaints and are also known emitters of ammonia. In this paper an experiment is described which compared the effectiveness of two abatement compounds, clinoptilolite and De-Odorase®, when used in broiler production. Two sites were used which had almost identical buildings, each with two rooms, and the same strain of bird. Clinoptilolite was used on one site and De-Odorase® on the other. Once a week ventilation rate, ammonia concentration and odour concentration were measured, to determine the effects of the additives. We also measured temperature, relative humidity and carbon dioxide concentration to confirm that the control and test rooms had similar micro-climates. In the room treated with clinoptilolite the ammonia concentration was statistically significantly higher than in the control and the total mass of ammonia emitted was 50% greater. In the De-Odorase® experiment the mean ammonia concentration in the treated room in the final week was 38% lower than in the control and the total mass of ammonia emitted from the treated room was 50% lower. There was no statistically significant reduction in the odour concentration or odour emission rate for either of the additives used.

Seasonal Diet Affects Ammonia Emissions from Tie-Stall Dairy Barns

Federal and state regulations are being promulgated under the Clean Air Act to reduce hazardous air emissions from livestock operations. Although much is known about air emissions from livestock operations in Europe, few data are available on emissions from livestock facilities in the United States and the management practices that may minimize these emissions. The objective of this study was to measure seasonal and diet effects on ammonia emissions from experimental tie-stall dairy barns located in central Wisconsin. Four experimental chambers each housed 4 lactating Holstein dairy cows for three 28-d trial periods corresponding to spring, early fall, and winter. A 4 x 4 Latin square statistical design was used to evaluate 4 diets [corn silage (CS)- or alfalfa silage (AS)-based diets at low or high crude protein] in each chamber for a 4-d ammonia monitoring period. Partially due to higher crude protein levels, average ammonia-N emissions during spring (18.8 g/cow per d) were approximately twice the emissions recorded during early fall (8.4 g/cow per d) and 3 times greater than emissions during winter (6.7 g/cow per d). Ammonia-N emissions accounted for approximately 1 to 3% of consumed feed N, 2 to 5% of excreted manure N, and 4 to 11% of manure ammonical N. Nighttime ammonia emissions were on average 30% lower than daytime emissions. Forage type did not affect ammonia emissions during winter or early fall. Only during early spring were ammonia emissions lower from chambers containing cows fed low-CP diets than from cows fed high-CP diets. Of the total chamber N inputs (feed and bedding), 93, 91, and 95% were recovered in N outputs (milk, manure, body weight change, and ammonia N) during spring, early fall, and winter trials, respectively. Confidence in the accuracy of ammonia emission results was gained by the relatively high chamber N balances and favorable comparisons of study data with published relationships among the variables of feed N intake, milk urea N, manure N, and urine N excretion, and ammonia emissions.

Modelling the spatial distribution of ammonia emissions in the UK

Ammonia emissions (NH3) are characterised by a high spatial variability at a local scale. When modelling the spatial distribution of NH3 emissions, it is important to provide robust emission estimates, since the model output is used to assess potential environmental impacts, e.g. exceedance of critical loads. The aim of this study was to provide a new, updated spatial NH3 emission inventory for the UK for the year 2000, based on an improved modelling approach and the use of updated input datasets. The AENEID model distributes NH3 emissions from a range of agricultural activities, such as grazing and housing of livestock, storage and spreading of manures, and fertilizer application, at a 1-km grid resolution over the most suitable landcover types. The results of the emission calculation for the year 2000 are analysed and the methodology is compared with a previous spatial emission inventory for 1996.

Odour emission arising from application of livestock slurries on land: Measurements following spreading using a micrometeorological technique and olfactometry

Livestock slurries were applied to grass or arable land, following which a simplified, micrometeorological technique was used in the collection of odorous air samples. On arable land, pig slurry was either left on the soil surface as a control or incorporated by means of a plough, rotary harrow or rigid tines. Odour concentration (odour units per m3 air) was subsequently determined by dynamic dilution olfactometry and rates of odour emission (odour units per second) calculated. From grassland, odour concentrations were greater for pig than for cattle slurry, especially when the former had been withdrawn from the settled layers near the bottom of a storage pit. The pattern of odour emission decayed exponentially with time; high rates of emission during the first few hours were followed by much lower rates between 6 and 60 h after application with small diurnal fluctuations. On arable land, ploughing immediately after application reduced the rate of odour emission during the first hour by 85% and rotary narrowing reduced it by 45% whereas the result when rigid tines were used was similar to the control. A worthwhile reduction (52%) in total emission (odour units) over 48 h was achieved only by immediate ploughing. No reduction in total emission was detected when incorporation, by any means, was delayed for 3 to 6 hr after slurry application.

An assessment of nitrification inhibitors to reduce nitrous oxide emissions from UK agriculture

A trial was conducted consisting of 14 experiments across sites in England of contrasting soil type and annual rainfall to assess the effectiveness of nitrification inhibitors (predominantly dicyandiamide (DCD) but limited assessment also of 3, 4-dimethylpyrazole phosphate (DMPP) and a commercial product containing two pyrazole derivatives) in reducing direct nitrous oxide (N2O) emissions from fertilizer nitrogen (N), cattle urine and cattle slurry applications to land. Measurements were also made of the impact on ammonia (NH3) volatilization, nitrate (NO3−) leaching, crop yield and crop N offtake. DCD proved to be very effective in reducing direct N2O emissions following fertilizer and cattle urine applications, with mean reduction efficiencies of 39, 69 and 70% for ammonium nitrate, urea and cattle urine, respectively. When included with cattle slurry a mean, non-significant reduction of 56% was observed. There were no N2O emission reductions observed from the limited assessments of the other nitrification inhibitors. Generally, there were no impacts of the nitrification inhibitors on NH3 volatilization, NO3− leaching, crop yield or crop N offtake. Use of DCD could give up to 20% reduction in N2O emissions from UK agriculture, but cost-effective delivery mechanisms are required to encourage adoption by the sector. Direct N2O emissions from the studied sources were substantially lower than IPCC default values and development of UK country-specific emission factors for use in inventory compilation is warranted.