LAUSR

Swine manure is kept in outdoor storages until it is applied to cropland. Anaerobic conditions facilitate microbial methane (CH4 ) production at a rate that depends on temperature. Manure CH4 emissions can be the largest contributor to the carbon footprint of pork. Despite the importance of CH4 , the actual emissions in cold temperate climates are highly uncertain. This study measured emissions from a single-cell earthen manure storage at a commercial swine farm near Brandon, Manitoba, for three years. Complimentary lab measurements were done to assess CH4 potential (i.e. B0 ). The manure storage regularly received manure from the barn and was only emptied in October. In the summer, manure temperature was usually lower than air temperature, with the manure temperature (averaged across depths) warming to between 15°C and 18.5°C for only 9 weeks. Emissions of CH4 were low, with the CH4 conversion factor (MCF) being between 3.0 and 11.0%, depending on the year (using the IPCC 2019 default B0 ). Scaled by the number of swine reaching 125 kg market weight each year, CH4 emissions were between 250 g CH4 animal-1 and 902 g CH4 animal-1 . Laboratory measurements of CH4 production potential scaled by VS were 335 mL CH4 g-1 VS at 37°C; perhaps lower than the IPCC 2019 default value due to barley in the ration and degradation in the under-barn pit prior to transfer outdoors. Taken together, the low manure temperatures, short warm-season, and barley in the ration, suggest that emissions from swine manure in cold climates like western Canada are considerably lower than previously estimated based on default factors. Limited period for CH4 production as manure was above 15°C only 9 weeks/y. Methane potential was lower than IPCC 2019 default, and comparable to barley-based studies. Emissions were between 250 g animal-1 and 902 g animal-1 , varied by year. Low MCF of 5.9% to 8.0% on average, depending on the B0 used. Emissions from the under-barn manure pit were not measured and warrant further study. This article is protected by copyright. All rights reserved.