A human-portable mass flux method for methane emissions quantification: controlled release testing performance evaluation

Abstract. Quantifying methane (CH4) emissions from anthropogenic sources is essential for compliance, inventory, and verification efforts. One established mass balance approach is the mobile flux plane method, in which emissions can be estimated from measurements of CH4 at various heights. Most traditional applications require either a drone or aircraft, both of which can be expensive, or limiting to deploy in all situations. To broaden applicability and improve practicality, we adapted the flux plane method using a long telescoping pole and backpack-mounted CH4 sensor. We explored accuracy through 44 controlled release experiments (0.2–5.6 kg CH4 h−1) from a 2.4 m stack. Measurements were taken at 6 heights (0.8–5.6 m) by walking transects 10–30 m downwind. The data yielded a mean relative error of −10.1 %, with 68 % of estimates within ±38.3 % of true values. Results are comparable to drone-based methods. We also tested an optimized Gaussian plume model using partial vertical profiles to address issues where the pole could not measure the top of the plume. This approach was slightly less precise than the flux plane method and had less bias. Overall, results show that multi-level, telescoping pole-based CH4 measurements combined with flux plane or Gaussian models can (i) quantify emissions from elevated sources in a logistically practical manner with results comparable to other widely used mobile quantification methods, and (ii) quantify sources emitting CH4 at low rates owing to the close-range capability of the method, complementing other mobile methods such as vehicle-based systems, aircraft, and satellites that generally measure higher-emitting sources.