DIAL Measurements of Fugitive Emissions from Natural Gas Plants and the Comparison with Emission Factor Estimates

Natural gas processing is a major industry in Alberta, Canada, and a significant source of fugitive emissions of both methane and volatile organic hydrocarbon (VOCs). This project investigated fugitive emissions at natural gas processing plants in Alberta using two complementary optical measurement methods. At five gas plants, the fugitive emissions of methane and hydrocarbons ethane and larger (C2+ hydrocarbons) were measured and quantified using Differential Absorption Lidar (DIAL). The DIAL was also used to measure emissions from process flares at two of the gas plants. At two of the plants, a gas leak imaging camera was used to locate individual hydrocarbon leaks. For the five gas plants surveyed in Alberta, DIAL measured methane emissions ranged from 100 to 146 kg/hr and C2+ hydrocarbon emissions ranged from 38 to 342 kg/hr. Compressors and condensate storage tanks were two significant emission sources at all of the gas plants. Process flares operating on pilot were typically responsible for 10 to 15% of the total methane emissions. At two gas plants the DIAL measured emissions of methane, VOCs and benzene were compared with values calculated using emission factor methods. Measured emissions of methane and VOCs were four to eight times higher than the emission factor estimates. The largest differences between measured values and estimates were for the flares and storage tanks. DIAL measured values gave a more realistic evaluation of revenue lost as fugitives than the industry accepted estimation methods, leading to an increased incentive to improve leak detection and repair.