Continuous on-farm measurement of Ammonia emissions in dairy barns

Oral presentation at XIX World Congress of CIGR in Antalya, Greece.

Agrinnotech designed and tested the practical emission measurement system.

ABSTRACT

Maarit Hellstedt, Natural Resources Institute Finland (Luke)

Hannu E S Haapala, Agrinnotech

Accurate assessment of national gaseous emissions needs measurements from different practical situations. The measurements need to be done in a proper way so that the results would represent the actual situations accurately enough.

In this study, measurements of Ammonia emissions were conducted in Finland at insulated and uninsulated stationary and loose-housing barns with different manure management and littering systems. The emission measurement instrumentation was done with a new setup enabling accurate results in both space and time. Usability of the measurement results and instrumentation were assessed.

One-week measurement sessions were done in a total of 24 sessions, i.e. six barns during all the four seasons. Continuously measuring Dräger PAC 7000 Ammonia monitors with a range of 0 to 300 ppm and a resolution of 1 ppm were used. The detection rate was set to 2 minutes in order to detect the dynamics of the emission. The Ammonia monitors together with CO2, temperature and RH gauges were placed inside the barns in three elevations (0.1, 1.0 and 2.5 meters) and in four to six locations, depending on the size of the barn. The ventilation rate in the barns was derived out of the measured C02balance. The Ammonia emission was then calculated based on the Ammonia concentrations and the ventilation rate.

According to the emission measurement results the loose-housing barns had significant differences in Ammonia emissions both during the seasons and between the farms as well, the level being mostly under 5 g/cow/day. In stationary barns the emission was less, under 3.5 g/cow/day. The emission level for loose-housing barns is considerably lower than the figures that have been previously used in national calculations. For stationary barns the situation is opposite. Loose-housing, however, is the dominant housing system in future. Consequently, the Ammonia emission level in Finland might be much lower than projected in the previous modelling.

The results concerning the implementation point out the importance of understanding the local circumstances and the ability to make the measurement design accordingly. Since there were several instrumentation locations the positioning of sensors could be evaluated. The dense detection rate could be used to reveal emission fluctuations and assess the effect of different detection rates on the reliability of measurements.

Instrument locations need to be derived from the barn layout and space. The continuous measurement principle with dense detection rate and relevant instrument locations allowed the researchers to find daily and momentous fluctuations in emission rate that were caused by the individual management practices on the farms and disturbances in them. These might explain the large variation in emission measurements that have been done before with inadequate instrumentation, i.e. using random locations or unsuitable detection rates.

The measurement principle utilized enables a more precise analyse of the differences of barns. The price-quality ratio of instrumentation limits the practical usability of methods. Research and inspection have different requirements from those of farm level. Continued studies are needed to develop optimised methods for farm level.

 

Key words: ammonia emission, measurement, accuracy, dairy production

 

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