A new technique to measure CO mixing ratio at industrial stacks plumes based on Raman Lidar remote sensing.

Carbon dioxide (CO) emissions from industrial point sources are one of the main driving factors contributing to uncertainties in CO emissions from fossil fuels. This study demonstrates, for the first time, the feasibility of a portable Raman Lidar system that is cost-effective and employs simple optics for the monitoring of anthropogenic CO emissions from stack sources. Two outdoor field campaigns were conducted to investigate emissions from waste combustor stacks in South Korea. In Haman, we examined the CO enhancement caused by emissions and estimated the CO instant emission flux over a waste combustor stack, which was located 440 m away from the Lidar. The CO volume mixing ratio peaked at 856.05 ppmv on the night of August 22, 2022, demonstrating effective CO source capture. Higher standard deviations on the night of August 22 were correlated to calm and light wind conditions. Instant emission fluxes were calculated at 265.6 kg/h (night of August 15) and 622.6 kg/h (night of August 22). Interestingly, the CO emission flux over the stack varied significantly with time, which implied the importance of continuous CO emission tracking. In Seoul, CO emission measurements were conducted on April 27, 2022, and a broader CO plume was detected compared to the observations in Haman. Instant emission fluxes were quantified at 771.3 kg/h (22:38) and 623.4 kg/h (22:49) over the stack, which was located 820 m away from the Lidar. Furthermore, the performance of the Raman Lidar was evaluated based on the comparison between Lidar measurements and data collected from in situ CO sensors. The outcomes validated the high accuracy of the Lidar under outdoor conditions (averaged percent difference = 0.06 %). Our study highlights the efficacy of Raman Lidar in tracking high CO emissions, thereby contributing to the quantification of greenhouse gas emissions and supporting global climate action initiatives.