Manure Management Practices for Mitigation of Gaseous Emissions from Naturally Ventilated Dairy Barns

How Does Management Impact Ammonia, Hydrogen Sulfide & Greenhouse Gases In Dairy Barns?

Emissions of pollutant gases from dairy barns are dependent on manure retention time in the barn and the quality of flushing water (for manure-flush systems). Strategies for mitigating air emissions from barns thus are a function of manure management either via optimal flushing or scraping, and pretreatment of flushing water.

What did we do?      

Ammonia (NH3), hydrogen sulfide (H2S), and greenhouse gases (CO2, CH4, and N2O) emissions, under different manure collection strategies, from a naturally ventilated dairy barn housing about 850 lactating Holstein cows were measured using an on-site real-time monitoring system. The manure collection strategies evaluated included: (i) altering manure-flushing frequency, (ii) alternating flushing and scraping to remove manure, and (iii) manure solids separation system via centrifugation of the flush water.

What have we learned?

Doubling flushing frequency (every 3 h flushing) did not significantly affect NH3 emission (25.5 g cow-1 d-1) compared to the normal every 6 h flushing (24.5 g cow-1 d-1) but reduced CO2 emission by 7.3%. On the hand, H2S, CH4, and N2O emissions were 1.3, 176% and 18.5% higher at the 3-h flushing schedule than at the normal 6-h flushing schedule. Flushing at half the frequency (every 12 h) reduced H2S, CO2, and CH4 by 59.4, 19.8 and 28.5%, respectively. Alternating manure flushing and manure scraping (or vacuuming) every 6 h, decreased CO2, CH4, and N2O emissions by 13.0, 7.8 and 19.5% compared to normal 6-h manure flushing alone. Use of centrifuged water for manure flushing significantly improved emissions mitigations more than all other strategies. Emissions of all the five gases decreased by 43.0 % for NH3, 37.3 % for H2S, 1.2% for CO2, 3.7% for CH4, and 51.7 % for N2O under the latter practice.

Future Plans  

Evaluation of other manure management practices which have not previously or adequately been tested at full-scale facilities or operations.


P.M. Ndegwa, Associate Professor, Biological Systems Engineering, Washington State University, PO Box 646120, Pullman, WA 99164, USA

H.S Joo, G.M. Neerackal, X. Wang; Department of Biological Systems Engineering, Washington State University, Pullman, WA.; and J.H. Harrison; Department of Animal Sciences, Washington State University, Puyallup, WA.

Additional information

• Joo H., P. Ndegwa, G. Neerackal, X. Wang, J. Harrison, J. Neibergs. 2013. Effects of manure management on ammonia, hydrogen sulfide, and greenhouse gases emissions from naturally ventilated dairy barns. ASABE Annual International Conference. Paper number 131593447; Kansas City, Missouri, July 21 – July 24. (doi:

• Neerackal, G.M., H.S. Joo, P.M. Ndegwa, J.H. Harrison. 2014. Manure-pH management for mitigating ammonia emissions from manure-flush dairy barns. ASABE and CSBE/SCGAB Annual International Meeting. Paper number 1892636; Montreal, Quebec, Canada, July 13-17.


This study was partially supported by funds from USDA-NRCS-CIG program (Grant No. 69-3A75-11-210), and Washington State University Agricultural Research Center. The cooperation and assistance of the collaborating producer is also acknowledged.

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