Methane emissions from LNG

The report analyzes methane emissions from LNG liquefaction, transport, and regasification, as well as small-scale distribution. It identifies key emission drivers such as fugitive leaks, boil-off gas (BOG) management, incomplete combustion in power generation and flaring, and gas-freeing during maintenance. The document provides a comprehensive set of best practices, including Leak Detection and Repair (LDAR) programs, the use of dry-disconnect couplings, reliquefaction units, and vapor recovery systems to minimize the climate impact of the LNG supply chain.

• Methane emissions in the LNG value chain are driven by five root causes: leaks, gas freeing processes, boil-off gas, power production, and excess gas.
• In the large-scale LNG chain, the liquefaction and carrier transport stages are likely the highest sources of methane emissions. Liquefaction emissions are primarily caused by incomplete combustion from energy generation and flaring, while carrier emissions stem from incomplete combustion and the venting of boil-off gas.
• Small-scale LNG operations can have significantly higher methane emissions relative to throughput compared to large-scale operations, largely due to the venting of over-pressure.
• Fugitive leaks from equipment like pumps, compressors, and pneumatic devices are a major emission source across all LNG stages. Implementing comprehensive Leak Detection and Repair (LDAR) programs and using zero-leak valve technologies are identified as key mitigation strategies.
• Boil-off gas (BOG) is an inherent challenge because LNG warms over time, expanding to 600 times its liquid volume. Best practices for managing BOG include reliquefaction, routing gas to power generation, using vapor recovery units (VRUs), or converting the gas to compressed natural gas (CNG).
• Incomplete combustion in power generation is a significant source of emissions, particularly in gas engines, which emit far more methane than gas turbines. For example, lean-burn spark ignited gas engines emit approximately 350 g of methane per GJ of fuel, whereas gas turbines may emit around 4 g per GJ.
• The transfer of LNG between tanks, ships, and trucks poses emission risks during the inerting and disconnection processes. The use of dry-disconnect couplings can eliminate the need for nitrogen purging and reduce spillage and leaks by up to 85%.
• Flaring is used for safety and pressure management but can be a major emission source if malfunctioning or inefficient. Mitigation includes Flare Gas Recovery (FGR) systems, which can reduce flare and vent gas by up to 100%.
• Maintenance and irregular events, such as the cooling down of liquefaction facilities or dry-docking of carriers, generate significant emissions. Automating the cooldown process of the main cryogenic heat exchanger can reduce flaring volume by 50%.

APA

Saunier, S., Jilani, M., & Brown, P. F. (n.d.). Methane emissions from LNG. Clean Air Task Force. https://cdn.catf.us/wp-content/uploads/2021/09/21091747/LNG-Methane-best-practice-29-Sept-2021.pdf?swpmtx=676e6b2aa1e2193d77bc62b71d1a48a0&swpmtxnonce=71a91ab03e

Chicago

Saunier, Stephanie, Mehak Jilani, and Peter Føllesdal Brown. Methane emissions from LNG. Clean Air Task Force, n.d. https://cdn.catf.us/wp-content/uploads/2021/09/21091747/LNG-Methane-best-practice-29-Sept-2021.pdf?swpmtx=676e6b2aa1e2193d77bc62b71d1a48a0&swpmtxnonce=71a91ab03e.

Wikipedia

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BibTeX

@techreport{saunierndmethane, author = {Saunier, Stephanie and Jilani, Mehak and Brown, Peter Føllesdal}, title = {{Methane emissions from LNG}}, institution = {Clean Air Task Force}, url = {https://cdn.catf.us/wp-content/uploads/2021/09/21091747/LNG-Methane-best-practice-29-Sept-2021.pdf?swpmtx=676e6b2aa1e2193d77bc62b71d1a48a0&swpmtxnonce=71a91ab03e}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }