Novel monitoring approach for seasonally resolved continuous methane emission measurements from open digestate storage

: Methane (CH 4 ) emissions from livestock manure storage are a significant contributor to agricultural greenhouse gas emissions, yet long-term field measurements capturing the annual progression of emission rates remain scarce. This study presents a novel approach for continuous monitoring of CH 4 emissions from open, non-gas-tight digestate storage at a full-scale manure-based biogas plant in Germany. Measurements were conducted over an entire annual cycle. Results reveal pronounced seasonal differences in digestate temperature, with mean values of 14.4 ± 2.5 °C in winter/spring and 23.0 ± 2.8 °C in summer/autumn, accompanied by variations in storage fill level. CH 4 emission rates also followed this pattern, with average rates of 0.12 ± 0.04 g CH 4 m -3 h -1 during colder months and 0.22 ± 0.06 g CH 4 m -3 h -1 during warmer months, corresponding to cumulative annual losses of 2.4 % of total CH 4 production. In addition, residual gas potential (RGP) analyses at 39 °C showed substantial variability over the year, ranging from 75-135 L CH 4 kg -1 volatile solids (VS), with consistently higher values observed during cooler periods compared to summer campaigns.