A dispersion-model-based method is an alternative to traditional micrometeorological techniques for determining tracer emissions. The method combines an atmospheric dispersion model with field observations of tracer concentration C, to infer the tracer emission rate Q from a source. The potential benefits of the method are experimental simplicity, no restriction (in principle) to an ideal site, and flexibility in the type & location of C measurement used. The objective of this study was to examine the accuracy of this method, built around a backward Lagrangian stochastic dispersion (bLS) model for the surface layer, for estimating Q from a small surface source. Our study site was an extensive flat short-grass surface in Alberta, where a 6 m x 6 m synthetic surface source was used to release methane at a known rate. During the experiment an open-path laser measured 15 minute line-average methane concentration for a variety of path lengths and locations (path lengths to 200 m, and a maximum downwind distance of 200 m). The bLS model was then used to infer Q for the specific meteorological conditions. Our presentation will discuss the agreement between this inferred Q and the actual emission rate.