Determining methane emissions from biogas plants - Operational and meteorological aspects

A micrometeorological method, combining an inverse dispersion technique with path-integrated concentration measurements, was applied on an Austrian biogas plant over the period of more than one year to determine emissions of the whole plant. Measurement campaigns were conducted to characterize the emission response to operational activities (e.g. digestate management) and meteorological changes. When digestate storage tanks were filled, an average emission rate of 7.2 kg CH4/h (approx. 4% of the calculated CH4 production) was determined, while 5.4 kg CH4/h of emissions (approx. 3% of the calculated CH4 production) were quantified after the tanks had been emptied. It could be observed that besides the operation mode (e.g. filling level or agitation of the openly stored digestate, maintenance), the meteorological conditions such as wind speed and solar radiation (e.g. heat flux) can also affect the emission rate.