Jesper Nørlem Kamp

Solid–liquid AC:separation is proposed to mitigate ammonia emission after field application of slurry, but evidence for pig slurry and digestate remains limited, particularly when emission from both fractions is included. This study quantified ammonia emission from unseparated pig slurry and digestate and their corresponding liquid and solid fractions across six field trials using dynamic flux chambers. Additional trials assessed biochar amendment to separated fractions. Application of liquid fractions reduced emission by 58% (digestate) and 71% (pig slurry) relative to unseparated materials, while emission from solid fractions was highly variable and, in some cases, exceeded those from unseparated slurry (% TAN). Aggregated ammonia emission, calculated by combining fraction-specific losses with separation efficiency, was consistently lower than from unseparated slurry under most scenarios (reductions: 29–88%). Because separation efficiencies could not be measured directly in this study, these aggregated, system-level estimates rely on literature-derived TAN partitioning scenarios. In the tested materials and at the tested amendment rates, biochar addition tended to increase ammonia emission, likely due to increased pH and dry matter concentration. Results demonstrate that separation reduces ammonia emission when evaluated at the system level but requires appropriate management of solid fractions.

Accurate analyses of liquid animal manure (slurry) from full‐scale slurry storage tanks are essential for effective nutrient management in agriculture. Inadequate or inconsistent sampling methods and improper storage conditions can lead to significant inaccuracies in nutrient analysis of slurry. This study evaluates the impact of different slurry sampling methods, storage types, and durations on the physical and chemical properties of slurry. Slurry was sampled using three different sampling methods in the same full‐scale tank both before and after mixing. Samples were stored at 5°C and −18°C for different durations (1–24 weeks) to assess changes in physical and chemical properties of the slurry. The analyzed parameters were ammonium, total nitrogen, total phosphorus, sodium, dry matter, volatile solids, and pH. The results show that the measured parameters varied considerably with sampling methods, in some cases by up to 80%–100%. The largest differences were observed for dry matter and total phosphorus between top and bottom samples in the unmixed tank, reflecting sedimentation effects. Profile sampling gave similar results as mixing prior to sampling. Storage at 5°C maintained sample integrity over 4 weeks, while storage at −18°C led to substantial changes in pH. Our findings indicate that proper sampling is crucial for representative analysis and that storage conditions can influence pH over extended periods.

Gaseous emissions from slurry storage tanks represent significant environmental and climate challenges. Accurate measurements of these emissions are essential for understanding their impact and developing effective mitigation strategies. However, measuring emissions of methane, ammonia, and nitrous oxide from full-scale slurry storage tanks can be challenging and it is practically impossible to obtain replicate measurement of the same slurry or test treatments under identical conditions.To overcome this challenge, Computational Fluid Dynamics (CFD) modeling was used to investigate suitable dimensions for small-scale tanks. A tank diameter of 2.4 m and a height of 1 m was found suitable for emission measurements. As a method for measuring the emissions the Micrometeorological Mass Balance (MMB) method, where concentration and wind speed is measured at multiple heights above the tank, is a promising candidate as it has been proven to work on full-scale tanks for methane (Kariyapperuma et al., 2018; Park et al., 2010).The plan was to validate the use of MMB on the small-scale tank while measuring in parallel with the backward Lagrangian Stochastic (bLS) method that have previously been used on full-scale slurry tanks (Lemes et al., 2022). Concurrent measurements with MMB and bLS were not useful as the concentration differences used for bLS were too small to estimate emissions. The measurement on pig slurry showed MMB emissions for methane and ammonia comparable to baseline emission in a recent review (Kupper et al., 2021), but the concentration response for ammonia indicated that it is questionable using a closed path instrument to measure ammonia emissions with MMB. In another validation experiment with IDM and MMB a known quantity of gas was released from a grid with 24 critical orifices inside the small-scale tank. In this case, bLS had a good recovery whereas MMB did not. The discrepancy was likely caused by the gas being released from discrete points and not uniformly from the entire surface. In a third validation experiment, MMB was compared to the Tracer Gas Method (TGM), where a known quantity of gas was released at three positions just below the slurry surface. The TGM and MMB emissions from methane agreed well in some intervals, but differed greatly in others, highlighting the challenges of measuring emissions from a small tank.The observed issues emphasize the complexity of validating emissions from small-scale slurry tanks. Downscaling the tank also downscales emissions, which can be an issue using some methods and thereby making it difficult to do cross validation with different methods in parallel.Downscaling provides opportunities to investigate natural variations and emissions of different slurry types under the same weather conditions in replicates, but the choice of an appropriate micrometeorological method is a complex challenge. References:Kariyapperuma et al.: Agric. For. Meteorol., 258, 56–65, doi:10.1016/j.agrformet.2017.12.185, 2018.Kupper et al.: Biosyst. Eng., 204, 36–49, doi:10.1016/j.biosystemseng.2021.01.001, 2021.Lemes et al.: ACS Agric. Sci. Technol., 2(6), 1196–1205, doi:10.1021/acsagscitech.2c00172, 2022.Park et al.: Agric. For. Meteorol., 150(2), 175–181, doi:10.1016/j.agrformet.2009.09.013, 2010.

Field-applied liquid animal manure (slurry) is a significant source of ammonia (NH₃) emission, which is harmful to the environment and human health. To evaluate mitigation options, reliable emission measurement methods are needed. A new system of dynamic flux chambers (DFCs) with high-temporal-resolution online measurements was developed. The system was investigated in silico with computational fluid dynamics and tested using three respective field trials, with each trial assessing the variability in the measured emission after application with trailing hose at different scales: manual (handheld) application, a 3 m experimental slurry boom, and a 30 m farm-scale commercial slurry boom. For the experiments with machine application, parallel NH₃ emission measurements were made using an inverse dispersion modeling method (backward Lagrangian stochastic, bLS, modeling). The lowest coefficient of variation among replicate DFC measurements was obtained with manual application (5 %), followed by the 3 m slurry boom (14 %), and lastly the 30 m slurry boom (20 %). Conditions in DFCs resulted in a consistently higher NH₃ flux than that measured with the inverse dispersion technique, but both methods showed a similar emission reduction by injection compared with the trailing hose: 89 % by DFC and 97 % by bLS modeling. The new measurement system facilitates NH₃ emission measurement with replication after both manual and farm-scale slurry application with relatively high precision.