Perspectives on peak liquid manure temperature with implications for methane emissions.

Methane emissions from liquid manure storage are currently estimated with a methane conversion factor (MCF) based on manure temperature inputs or air temperatures as a substitute in the 2019 IPCC Tier 2 method. However, differences between peak manure temperature and peak air temperature (T diff ) in warm seasons are likely to occur and result in poor estimates of MCF and methane emissions. To address this concern, this study aims to investigate the relationship between the T diff and ratio of manure surface area to manure volume (R s:v ) using a mechanistic model and by analyzing farm-scale measurement studies across Canada. Positive correlations between T diff and R s:v were found using a modelling approach and from farm-scale results (r = 0.55, P = 0.06). T diff ranged from -2.2 to 2.6 in farm-scale results mainly collected from eastern Canada. We suggest that manure volume and surface area, in addition to removal frequency, could be used to estimate T diff and be part of the criteria for improving manure temperature estimates which could lead to improved estimates of MCF. This article is protected by copyright. All rights reserved.