A new technique to measure CO2 mixing ratio at industrial stacks plumes based on Raman Lidar remote sensing.

Carbon dioxide (CO2) emissions from industrial point sources are one of the main driving factors contributing to uncertainties in CO2 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 CO2 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 CO2 enhancement caused by emissions and estimated the CO2 instant emission flux over a waste combustor stack, which was located 440 m away from the Lidar. The CO2 volume mixing ratio peaked at 856.05 ppmv on the night of August 22, 2022, demonstrating effective CO2 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 CO2 emission flux over the stack varied significantly with time, which implied the importance of continuous CO2 emission tracking. In Seoul, CO2 emission measurements were conducted on April 27, 2022, and a broader CO2 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 CO2 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 CO2 emissions, thereby contributing to the quantification of greenhouse gas emissions and supporting global climate action initiatives.