Verdamping uit ligbodems van vrijloopstallen : oriënterende modelberekeningen = Water evaporation from bedding in dairy cattle freestall barns : model approach

Water evaporation from bedding in freestall dairy cattle houses was modeled. Calculated water evaporations from excreta in composting and non composting beddings were much lower in Holland than in Israel. A model approach to study the drying potential of bedding materials in freestall dairy cow barns under Dutch climate conditions was performed. Water evaporation from bedding in freestall dairy cattle houses was modeled. This was done as part of a feasibility study of freestall barns with different beddings under Dutch meteorological conditions. The beddings are made up of mixtures of soft composting, or non composting materials and animal excreta. Two available models on composting and drying were combined. The estimated water flux from urine and feces that is excreted on the bedding was integrated in the model approach. Model calculations were performed to compare the order of magnitude of evaporation from the bedding area under Dutch, Israeli and Minnesotan climate conditions and at 18 versus 9 m2 of bedding area per animal. Calculated water evaporations from excreta in composting and non composting beddings were much lower under Dutch weather conditions than under Israeli conditions. The calculated evaporation under cold Minnesotan winter conditions was lower and in hot Minnesotan summer was higher than under Dutch conditions. The calculated evaporation from a bedding that is composting was higher than from a non composting bedding. The calculated rate of composting was strongly dependent on the heat flux that results from conversion of organic matter and the heat loss from the bedding. The heat flux is strongly influenced by the air velocity above the bedding. High air velocities result in a large heat loss that may slow down or even inhibit the thermophylic composting process. The lower evaporation rate of inorganic beddings may be compensated to some extend by increasing the air velocity above the bedding. To keep the top layer of the bedding sufficiently dry it may also be searched for a bedding with a high fluid infiltrating capacity. By adding fresh bedding material or controlled drying of part of the bedding material outside the barn problems during adverse climate conditions may also be tackled. On farm pilot experiments with bedding materials and management are needed to test whether or not it is possible to keep the top layer of the bedding at an acceptable level of dryness under cold and moist Dutch weather condition

Simulating the effect of forces pit ventilation on ammonia emission from naturally ventilated cow houses with CFD

Atmospheric NH3, mainly originates from agricultural sources, can cause serious environmental problems related to eutrophication and soil acidification. Emissions from dairy houses are 15% of total agricultural NH3 emissions. Due to open buildings, existing abatement options are limited. Pit air separation was identified as a potentially efficacious option. In this study a model simulation of a commercial dairy cow building with slatted floor is presented. The model was solved for 12 cases, differing wind speed, direction and both air and manure temperature. For each case three solutions were obtained, which correspond a) to a building where a forced pit ventilation system is applied at capacity of 250 and 500 m-3 h-1 cow-1 and b) to a building without forced pit ventilation system. The results show that due to forced pit ventilation system, at 250 and 500 m-3 h-1 cow-1, the ventilation rate was increased 3.1% and 6.2% respectively. The contribution of the pit ventilation system to the total ammonia released from the pit during winter, ranged from 31-35%, 16-19% and 11-8%, for wind speed of 1.0, 4.0 and 8.0 m s-1 respectively. Correspondingly, during summer, the contribution of the system ranged from 44-48%, 20-21% and 12-9%. Although obvious benefits arise from a forced pit ventilation system, the main mass flow of ammonia from the pit still emitted through the building ventilation openings, especially at high wind speeds

Reductie van ammoniakemissie op vleesvarkensbedrijven via gecombineerde maatregelen = Reduction of ammonia emission from houses for growing-finishing pigs by combined measures

In this study the possibilities are shown to reduce ammonia emission from houses for growing-finishing pigs by a combination of feeding, simple housing en management measures

Is de vrijloopstal haalbaar in Nederland?

Vrijloopstallen zijn stallen, waarin de koe vrij kan rondlopen. Ze hebben geen ligboxen. De koeien lopen en liggen op een zachte bodem. De stal biedt kansen voor het dierenwelzijn en de diergezondheid. In het buitenland zijn ervaringen met bodems van compost, zand en gedroogde mest. Voor het Productschap Zuivel en het ministerie van LNV is een haalbaarheidsstudie gedaan naar de mogelijkheden in Nederlan

Oriënterend laboratoriumonderzoek naar ammoniakemissie uit bodempakketten voor vrijloopstallen = Laboratory study of ammonia emission from bedding materials of freestall dairy cattle houses

In the Netherlands there is growing interest amongst dairy farmers in new housing systems in which animal welfare and health are improved. A promising system in this area is a loose housing system (without cubicles) where cows have a large area with a soft bedding where they can both being active and rest, so called freestalls. Although these systems are already applied in the USA and Israel, little is known about the environmental impacts, and particularly the ammonia emission. The aim of this study was to get some first impressions of the suitability of different bedding materials, especially concerning ammonia emission. The ammonia emissions of simulated urinations were measured in a laboratory set up with several bedding materials. As non degradable materials, two types of sand with larger and smaller average particle size and one type of rubber shaving were tested. As degradable materials freshly produced press screwed manure (the solid fraction), without (1) and with (2) an added mixture of sawdust and wood chips, composted press screwed manure (3) and (4) mud (peat soil/clay) originating from the small channels in the grasslands in an area with a peat soil with a top soil layer of clay. One week before the laboratory experiment, each of the bedding materials was mixed with fresh dairy cattle feces, urine and press screwed manure to get a quick simulation of the excreta accumulation in beddings in freestalls. Into the non degradable materials less feces and less screw pressed manure were added to simulate an on farm partly removal of feces from the resulting beddings. After preparation the bedding-excreta mixtures were kept one week in boxes in a ventilated house, with similar conditions as in a cow house. After this week, the ammonia emission from a simulated urination was determined in a laboratory set up. The degradable variants were tested both after manually pressing (higher density) and without pressing (lower density) the bedding mixtures in the laboratory set up. Ammonia emissions were higher with the non degradable bedding materials than with the degradable materials. The emission of the mud bedding mixture was low after 4, 24 and 72 hours. The emission of the mixture of screw pressed manure, sawdust, and wood chips with added excreta was very low after 4 hours. However after 24 and 72 hours the higher density variant showed a remarkable increase of ammonia emission while the low density variant did not. Between the tested bedding variants substantial differences in ammonia emissions were measured. Only a quick and short simulation was done to get first impressions. In reality, longer term accumulation of excreta in the beddings may result in build up of layers, silting up and different conversion rates in the freestall beddings. This may result in higher or lower emissions. The ranking of bedding materials may change as a result of this. Further research, also on other gaseous emissions like greenhouse gasses, in real cow barns is recommended to study this time and conditions dependent phenomena in more detai

Measures to reduce ammonia emissions from livestock manures: now, soon and later

Various possible options to further decrease ammonia emissions from livestock manure were explored in a desk study. Techniques and their impact on the processes leading to NH3 production and volatilization are described. Research priorities are identified

Kelderlucht afzuigen uit melkveestallen lijkt perspectiefvol

Om de ammoniakemissie uit melkveestallen te verminderen is tot nu toe vooral aandacht besteed aan de vloeren in stallen. Voordeel hiervan is dat de vorming van ammoniak bij de bron wordt aangepakt. Nadeel is het spanningsveld tussen beloopbaarheid en emissievermindering. ASG onderzoekt daarom de mogelijkheden van het aanzuigen en zuiveren van kelderlucht. Modelberekeningen laten zien dat dit perspectiefvol i