How you measure emissions from open stable systems

Background and Objective

In organic farming an open yard is an inherent part of a cattle stable, especially when no grazing land access is possible. However, the assessment of the emissions of an open yard is difficult. Approving authorities regard open yards as an area source and use emission factors that are partly based on assumptions.

Aim of the project is the measurement of the emissions of the climate relevant gases from the open yard of a cattle stable. By this, we obtain objective data for planning and building permission procedures and check the existing stables with regard to their “environmental compatibility”. Thereby possible changes in the stable management could be recommended, which can improve the emission behavior without neglecting the animal protection.

Approach

In cooperation with the Thünen Institute of Agricultural Technology we investigate in a young cattle barn the emissions of gaseous substances, dust and bioaerosols from the stable and the open yard.

The measuring of the emissions of gaseous substances (NH₃, CO₂, N₂O and CH₄) is difficult because of the size of the open yard and the direct agency of the weather. One possibility to measure these emissions is the use of an active sampling hood.

Data and Methods

The open yard is virtually partitioned into a 1 m² grid. To each partition a dirt level is assigned. With the active sampling hood, which is described in the guideline VDI 3475 Blatt 1, measurements on the grid area are carried out randomly. In addition, the effect of a scraper that cleans the surface of the open yard is investigated both before and after the application.

Parallel to the measurements with the active sampling hood on the open yard, measurements of the gaseous substances inside the stable are carried out continuously. This is achieved by means of a multi gas monitor, which is controlled by a multipoint sampler.  In addition, parameters like wind direction and wind velocity in different heights inside the stable and in the surrounding of the stable are recorded. These measured values are required for the approximate calculation of the volume flow, which is a prerequisite for the determination of the emissions from the stable.

The above described approach enables to evaluate the environmental relevance of the gaseous emissions from the stable and the open yard separately.

Results

The results show that the NH3 concentrations from outdoor yard are higher than those from the background in the barn environment. Higher values occurred in isolated cases after the use of the scraper. The reason for this is assumed to be the tearing open of the dried manure surfaces. For the other gases investigated, no clear difference to the background concentration could be detected. Thus, NH3 primarily contributes emissions to the environment.