Thames Water has continued its industry-leading work to quantify emissions from sludge assets as part of the development of a proportionate approach to meet the Industrial Emissions Directive (IED) requirements. A five-day sampling campaign was conducted to assess diffuse methane emissions from sequential secondary digesters and dewatering buffer feed tanks using multiple measurement methods. Lindvall and EPA flux hoods were used for direct measurement from the tank surface, alongside leak detection and repair (LDAR) techniques, including optical gas imaging (OGI) and quantum lidar technologies, for a broader site-scale evaluation. In addition, the residual biogas potential (RBP) data was also gathered to complement on-site measurements. This presentation will outline the methodologies and experimental set-up, present the results of the sampling programme, and provide a comparative assessment of the approaches with respect to their ability to quantify diffuse emissions and their practical feasibility for on-site implementation.