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<p>Dairies emit roughly half of total methane (<span class="inline-formula">CH₄</span>) emissions in California, generating <span class="inline-formula">CH₄</span> from both enteric fermentation by ruminant gut microbes and anaerobic decomposition of manure. Representation of these emission processes is essential for management and mitigation of <span class="inline-formula">CH₄</span> emissions and is typically done using standardized emission factors applied at large spatial scales (e.g., state level). However, <span class="inline-formula">CH₄</span>-emitting activities and management decisions vary across facilities, and current inventories do not have sufficiently high spatial resolution to capture changes at this scale. Here, we develop a spatially explicit database of dairies in California, with information from operating permits and California-specific reports detailing herd demographics and manure management at the facility scale. We calculated manure management and enteric fermentation <span class="inline-formula">CH₄</span> emissions using two previously published bottom-up approaches and a new farm-specific calculation developed in this work. We also estimate the effect of mitigation strategies – the use of mechanical separators and installation of anaerobic digesters – on <span class="inline-formula">CH₄</span> emissions. We predict that implementation of digesters at the 106 dairies that are existing or planned in California will reduce manure <span class="inline-formula">CH₄</span> emissions from those facilities by an average of 26 % and total state <span class="inline-formula">CH₄</span> emissions by 5 % (or <span class="inline-formula">∼36.5</span> Gg <span class="inline-formula">CH₄</span>/yr). In addition to serving as a planning tool for mitigation, this database is useful as a prior for atmospheric observation-based emissions estimates, attribution of emissions to a specific facility, and validation of <span class="inline-formula">CH₄</span> emissions reductions from management changes. Raster files of the datasets and associated metadata are available from the Oak Ridge National Laboratory Distributed Active Archive Center for Biogeochemical Dynamics (ORNL DAAC; Marklein and Hopkins, 2020; <a href="https://doi.org/10.3334/ORNLDAAC/1814">https://doi.org/10.3334/ORNLDAAC/1814</a>).</p>