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DCA Publikationer Management effects on methane emission from stored digestate - insights from coupling heat transfer and microbial models DCA rapport, nr. 238, 2025 Af Henrik B. Møller, Sasha D. Hafner, Frederik R. Dalby & Christiane Romio  Methane emission from digestate stored after anaerobic digestion and effects of management are not well characterized. In this work a heat transfer model for digestate temperature and a microbial model for methane production were coupled to provide a tool for predicting methane emission from stored digestate. Measurements from full-scale storage tanks were used for parameter estimation and evaluation. The models predicted overall levels of annual emission with relative error under 20%. Predicted dynamics in emission rate over a year were roughly similar to measurements, with some exceptions where the model predicted a different annual pattern. Temperature was predicted accurately (mean absolute error < 3.2 °C). The coupled models can be used to explore potential effects of digestate properties, weather, tank conditions, delivery temperature, or other management practices on methane emission. The quantity of degradable substrate remaining in digestate is an important variable, and sensitivity to the delivery temperature depends on the digestate loading/emptying schedule, resulting from interactions between timing, heat transfer rates, substrate hydrolysis, and slow growth of methanogenic communities. Predictions do not include estimates of uncertainty, but uncertainty is undoubtedly high, and predictions will likely change as the models are refined. |