Implementation of the directive on industrial emissions (integrated pollution prevention and control); the Industrial Emissions Directive (IED), requires anaerobic digestion (AD) plants with an Environmental Permit to reduce fugitive emissions and ensure any channelled or point-source emissions into the atmosphere do not exceed the emission limit value (ELV) of 20 mg/m3 of total volatile organic carbon (TVOCs) including methane.

Methane can account for >95% of post-AD TVOCs, therefore, to meet the ELV for these channelled emissions, it is critical to extract the residual methane from the treated digestate using techniques such as degassing to harvest the dissolved and entrained methane, and deactivation to inhibit methanogenic microorganisms producing post-AD methane and biogas. However, effective mitigation is currently hindered by two main challenges including (i) a lack of comprehensive measurement data and (ii) the absence of robust, scalable best available technologies (BATs) that are proven for mitigating low-concentration methane emissions while also having low embodied carbon. This paper presents the results from a collaborative research project involving four UK water companies, Bluemethane, AD Ingenuity, and Cranfield University; focussing on degassing the digestate, and deactivating post-AD methanogenic activity. The investigation involves a series of systematically conducted experiments to quantify the impact of various physicochemical treatments on cessating methanogenesis. The findings as presented, demonstrate an opportunity for reducing TVOC emissions from liquid digestate using an innovative technique.