Whole-Site Quantification of Methane Emissions from 65 German Biogas Plants Reveals Systematic Underestimation in...

With around 9600 biogas plants, Germany has the largest biogas sector in Europe, where methane (CH4) losses can substantially counterbalance the climate benefits of this renewable energy source. Nevertheless, comprehensive empirical data on CH4 emissions and loss rates across different plant sizes and configurations in Germany remain limited. In this study, we quantified CH4 emissions at 65 biogas production sites using mobile measurement surveys combined with Gaussian plume dispersion modeling. Observed emission rates varied between 0.3 and 255 kg CH4 h-1, corresponding to size-dependent CH4 loss rates. Small plants averaged substantially higher losses of the produced CH4 (∼8.8%), whereas medium and large plants as well as upgrading facilities showed lower, more consistent loss rates of 2.9-4.3%. Using two different upscaling approaches, we estimate that German biogas plants emit approximately 360-370 kt CH4 yr-1, contributing ∼23% of Germany's total CH4 emissions. These sector-wide emissions exceed bottom-up estimates, highlighting a systematic underestimation in current inventories. Our results represent one of the most comprehensive measurement-based assessments of CH4 emissions from German biogas infrastructure to date, showing that this method could improve national CH4 budgets, and develop and verify mitigation strategies. The observed emissions further underscore the need for leak reduction and mitigation measures to preserve the climate benefits of biogas plants.