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

Area of Science:

• Agricultural Science
• Environmental Science
• Climate Change Research

Background:

• Current methane emission estimates for liquid manure storage rely on the 2019 IPCC Tier 2 method, using manure or air temperatures to determine methane conversion factors (MCF).
• Seasonal variations, particularly in warm periods, can cause significant differences between peak manure and air temperatures (T_diff), leading to inaccuracies in MCF and methane emission estimations.

Purpose of the Study:

• To investigate the relationship between the temperature difference (T_diff) and the ratio of manure surface area to manure volume (R_s:v) in liquid manure storage.
• To identify potential improvements for estimating methane conversion factors (MCF) and subsequent methane emissions from agricultural sources.

Main Methods:

• Utilized a mechanistic modeling approach to simulate the relationship between T_diff and R_s:v.
• Analyzed farm-scale measurement data from liquid manure storage facilities across Canada to validate model findings.

Main Results:

• A positive correlation was observed between T_diff and R_s:v, supported by both modeling (r = 0.55, p = 0.06) and farm-scale data.
• Farm-scale measurements indicated T_diff values ranging from -2.2 to 2.6°C, primarily from eastern Canadian locations.

Conclusions:

• Manure storage geometry (volume and surface area) and removal frequency are critical factors for estimating T_diff.
• Incorporating these factors into manure temperature estimation can enhance the accuracy of MCF calculations and reduce uncertainties in methane emission inventories.