Improving CH4 emission simulation for liquid manure storage tanks: Development of a manure temperature model in Manure-DNDC

Despite the significant impact of temperature on CH 4 emissions, process-based models have not included a comprehensive approach for simulating manure temperature. To fill the gap, we developed a physical process-based manure temperature model and integrated it into the full-farm DeNitrification DeComposition (Manure-DNDC) model. The temperature model used a surface energy balance approach and Fourier heat conduction to simulate stratified manure temperature in storage tanks. After testing with three years of new field observations on a dairy farm, results showed excellent performance on the modified model for both manure temperature (0.91 < d-index <0.99) and CH 4 emissions (0.92 < d-index <0.97). The modified model demonstrated a significant improvement (−48% to −2% PBIAS for total CH 4 emission) compared to the original model, particularly when manure temperature exceeded the air temperature. However, the improved model occasionally struggled to replicate daily CH 4 fluctuation. Additional studies are recommended to facilitate future model development.