Developing a greenhouse gas life cycle assessment framework for natural gas transmission pipelines.

As demand for natural gas increases, it is important to understand its life cycle emission intensity. A framework is developed for performing bottom-up greenhouse gas (GHG) life cycle assessment of natural gas transmission pipelines to assist project environmental assessments. Three large-scale pipelines in Canada were examined: Alliance mainline (50 million m³/d, 3000 km), Prince Rupert phase 1 (PR1, 57 million m³/d, 878 km), and Prince Rupert phase 2 (PR2, 102 million m³/d, 878 km). Fundamental engineering principles are used for calculation accuracy, with a sensitivity analysis to identify key parameters. The model boundary includes pipeline construction, operation, and decommissioning. The resulting transportation GHG emission intensities are 1.49, 0.77, and 1.78 gCO 2 eq/GJ.km for the Alliance, PR1, and PR2 projects, respectively. The operating phase represents 78%–95% of the overall emissions. Operating at higher pressures could reduce emission intensity by up to 49% by increasing flow efficiency. The research provides a user-friendly open-source template that can be used to examine alternative scenarios. Image 1 • Operating phase represents 78%–95% of the pipelines' overall emissions. • Transporting rich natural gas at high pressure can reduce emissions. • Pipeline emissions are most sensitive to flowrate and operating pressure. • Fugitive emissions are the largest source of uncertainty in the results. [ABSTRACT FROM AUTHOR]