Jasmine Liu | MEL Candidate | December 3, 2024
Mentors: Varun Narayan, Wanying Shi and Heather Jones | S&P Global Commodity Insights
Abstract
This project aims to assess methane emissions across key stages of the Liquefied Natural Gas (LNG) supply chain, focusing on shipping process. By integrating industry data and developing emission models, the study will quantify methane emissions from various ship types and technologies. The LNG shipping model enables the selection of specific LNG vessel, departure and arrival LNG terminals, routes, voyage speed, allowing users to calculate the total methane emissions during the shipping process, providing targeted strategies for reduction and improved environmental performance.
Introduction
Methane emissions from Liquefied Natural Gas (LNG) vessels contribute significantly to the environmental impact of LNG transport. These emissions are influenced by the type of propulsion systems used, which vary in efficiency and emissions profiles. Understanding the sources of methane emissions on LNG vessels and assessing the technical specifications of existing propulsion technologies is crucial to improving the environmental performance of the LNG supply chain. The shipping part of this study aims to identify key emission sources from LNG vessels and evaluate the technical characteristics of different propulsion systems to guide emission reduction strategies.
Methodology
The list of active LNG vessels, LNG terminals, and shipping distances is sourced from publicly available information. At the time of this study, measured data for engine slip and boil-off rates were unavailable for most carrier types. Emission estimates were therefore derived using delivery year as a proxy for technological advancements in containment and propulsion systems.
The Excel-based model is designed for user input with drop-down selections for embedded LNG vessels, terminals, and routes. It estimates boil-off gas separately for the laden and ballast legs while considering containment systems, allocating it between the propulsion and auxiliary systems. The model then calculates methane slip for both the propulsion and auxiliary systems separately while considering propulsion systems, with the final output being the total methane emissions from both components.
Additionally, the model is automated to calculate and export results for a selected route across all vessels. This feature is particularly useful for benchmarking multiple LNG vessels based on methane emissions or intensity for transporting cargo between a liquefaction facility (e.g., in the United States) and a regasification facility (e.g., in China).
Results and Discussion
The rate of methane slip is lowest for steam propulsion, second lowest for ME-GI, and highest for DFDE/TFDE propulsion
Using a round trip from the U.S. to China via the Panama Canal across all existing LNG carriers, methane emissions per mass of LNG delivered (kg CH4/t LNG) can be categorized into three groups:
- Steam/Steam Reheat propulsion fleet with the lowest value
- ME-GI/ME-GA/STaGE/X-DF propulsion fleet, the highest value in this group is about 2.7 times of the lowest one
- DFDE/TFDE propulsion fleet displays the widest range, with the highest value being approximately 6.8 times greater than the lowest value in this group
Conclusion
Variations in carrier capacity and technological advancements in LNG carriers significantly affect greenhouse gas emissions during LNG shipping. This study’s framework incorporates these factors, allowing efficient emissions calculations using a spreadsheet model for a high-level analysis with limited accuracy.
Contact
Jasmine Liu
eureka.chris+ubc@gmail.com