A Life-cycle Assessment of Canadian-produced Liquefied Natural Gas for Consumption in China

Natural gas consumption has increased in recent decades due to low prices and emissions benefits over coal. The greenhouse gas (GHG) benefits of natural gas over coal require a low upstream emissions profile, in particular with low fugitive emissions of methane. Furthermore, natural gas is unlike oil in that it is highly transport-constrained. Liquefied natural gas (LNG) allows for overseas shipping but comes at significant economic and energetic costs. We worked with a Canadian liquids-rich gas producer to better understand upstream fugitive emissions and assess their efficacy of leak detection and repair (LDAR) programs. We model emissions from their operations and perform life-cycle assessment (LCA) of a hypothetical scenario where they produce 1 billion cubic feet per day of LNG in coastal British Columbia, for consumption in Shenzhen, China. We determine the life- cycle GHG and criteria air pollutant emissions associated with such a project.

We find that the LDAR surveys have resulted in decreased number of emissions points and decreased site-wide emissions. Leaks that were fixed from LDAR surveys tended to remain fixed and did not reappear. Likewise, leaks that were not fixed tended to persist and did not go away on their own, indicating that leak persistence is very high. Consequently, LDAR surveys are resulting in emissions reductions, as long as detected leaks are fixed. Repeat LDAR surveys regularly found new emission sources, even without significant site changes occurring, supporting the idea that LDAR surveys must be done regularly to find and fix new emission sources that arise from equipment failure or breakdown.

We find that Canada-to-China LNG will result in fewer life-cycle GHG emissions than the same power generated using coal in Asian markets. Studies have estimated Chinese coal power emissions to be anywhere from 868 to 975 g CO2e/kWh, nearly double our results of 408.2 to 547.9 g CO2e/kWh. Our results are lower than prior studies due to low upstream emissions and more efficient LNG production assumptions. LCA studies of LNG have focused on upstream and liquefaction stages, but our work makes it clear that total emissions are dominated by end-use emissions. When considering the climate benefits and drawbacks of LNG, it is critical to understand how the gas will be used.