Covering and Flaring Manure Storage Units as a Methane Mitigation Strategy for Small- to Midsize Dairy Operations in...

Covering manure storages and flaring the captured methane (cap-and-flare) offers a technically feasible mitigation pathway for small- and midsize dairies that has received limited attention relative to anaerobic digestion (AD). While AD systems are more economically feasible for large operations, the dairy segment with fewer than 1,000 cows still produces approximately 34% of U.S. milk and remains largely unaddressed. We estimated technical CH4 mitigation potential under full cap-and-flare adoption using the IPCC Tier 2 model for 8,675 dairy farms across 38 US states. Under 100% adoption, liquid storage CH4 mitigation potential (GWP100 = 27) ranged from 5.53 MMT CO2e yr-1 (central 90% interval: 3.70-6.63) to 10.36 (central 90% interval: 6.93-12.42) depending on the Arrhenius activation energy and reference temperature constants applied, representing 16-30% of the CO2e attributed to dairy manure CH4 in the 2022 EPA Greenhouse Gas Inventory. These values represent an upper-bound technical potential rather than a projected deployment level. Average national Levelized Costs of Mitigation (LCOM) ranged from \$55 t-1 CO2e (conservative parametrization) to \$29 t-1 CO2e (upper-bound parametrization), positioning cap-and-flare as a cost-efficient CH4 mitigation option. Existing USDA-NRCS Conservation Practice Standard 367 provides an available incentive mechanism, although meaningful scale-up will likely require dedicated funding for infrastructure and technical assistance. These results suggest that cap-and-flare could complement AD as a mitigation pathway for U.S. dairy operations where AD is not economically viable.