Publications

A modular approach for quantification of nitrogen flows and losses along dairy manure management chains of different complexity

Qu, Qingbo; Groot, Jeroen C.J.; Zhang, Keqiang

Summary

Nitrogen (N) loss from manure management chains (MMCs) of dairy farms are substantial and variable. The complexity of MMCs varies dependent on the method of collection and the number of subsequent storage and processing technologies used. We developed a modular approach that quantifies total ammoniacal N (TAN) and organic N flows along MMCs with different complexity. Emission factors of different N species for manure treatment facilities in MMCs were established based on published values. Simulated N losses from various MMCs from nine published case studies ranged from 20 to 50% of excreted N. Comparisons between simulated and reported N losses showed deviations ranging from 0.05 to 40% for the whole MMCs. Larger deviations were caused by uncertainty about emission factors for open lots, grazing lands and anaerobic lagoons. Using the modular approach, we could identify the elements that caused the deviations and could revise the reported emission factors, resulting in reduction of deviations in N losses to less than 10%. Simulated N losses were within the range of estimates obtained from the application the present Tier2/Tier 3 methodology, which further validates the reliability of our estimates. We conclude that the modular approach allows adequate estimations of N losses along MMCs and can help to identify the sources of differences or deviations of N loss estimations by different approaches. Further research should focus on N losses from open lots, anaerobic lagoons and N transformation during storage, which could further enhance the accuracy of estimations for N flows and losses in MMCs.