Floor heating and heat exchanger as an ammonia mitigation technique for broiler housing

Ammonia (NH3) volatilization from broiler housings is an increasing source of ammonia emissions due to the growing demand of chicken meat. Since modern broiler housings represent mostly larger operations with several thousands of animals, deposition of NH3 in nearby natural or semi-natural ecosystems can be significant and often exceeds critical levels for reactive nitrogen. Therefore, mitigation techniques for NH3 volatilization are crucial. Emissions are strongly influenced by the consistence and the moisture of the litter. Techniques which keep the litter dry such as floor heating and heat exchangers are promising options.

We conducted a campaign over an entire production cycle at a farm with parallel emission measurements at two identical broiler housings with 9000 animals each. One building had no mitigation techniques and served as reference, while the other one was operated with floor heating and a heat exchanger (FH-HE). The production cycle in each housing was slightly offset with the Ref cycle lasting from 30^th of October until 1^st of December 2023 and the FH-HE cycle from 2^nd of November until 6^th of December 2023. We measured the inflow concentrations of NH₃ and CO₂ at each of the six air inlet channels and at all of the outlets (3 at the Ref and 4 at the FH-HE housings) using Dräger X-node sensors. The air exchange rate was determined with measuring fans placed at all of the outlets. After the measurement campaign, all sensors were exposed side by side in a nearby cattle barn during 20 days for intercomparison and subsequent correction of the individual sensors.

In-house concentrations ranged up to 18 ppm for Ref housing and up to 5 ppm for the FH-HE housing. Highest concentrations and emissions were measured at the end of the production cycle. The emissions over the entire production cycle was 16.9 kg NH₃ (Ref) and 1.8 kg for the FH-HE. The emissions were lower by a factor of approximately 9 for the FH-HE house as compared to the Ref. The litter was considerably drier in the FH-HE housing presumably due to the floor heating and the lower ventilation rate which was possible due the heat exchanger, which also led to a lower relative humidity. Additional measurement campaigns covering the winter and the summer seasons will include additional analyses of the moisture content and chemical composition of the litter to further elucidate the emission reduction achieved by the FH-HE. The absolute emission numbers of the present campaign will be evaluated based on an intercomparison with a wet chemical method. The ventilation rate based on a CO₂ balance calculation will be compared with the ventilation rate determined from the measuring fans. It will also be analyzed whether a simpler measurement setup based on fewer sensors can be employed to optimize the acquisition of reliable measurement data at reduced costs.