Abstract
Liquefied natural gas (LNG) has been considered as a substitute for diesel and heavy-fuel oil in heavy-duty trucks and marine vessels, respectively. However, the widespread adoption of LNG as a fuel is hampered by its uncertain potential to reduce greenhouse gas (GHG) emissions in comparison with diesel and heavy-fuel oil from the lifecycle standpoint. Methane is the main component of LNG and a potent GHG. In this study, the design and validation of a high-volume sampling (HVS) system are proposed to accurately measure methane emissions from the LNG fuel infrastructure, including experiment designs for calibration and system validation, and uncertainty analysis. The accuracy of HVS measurements is tested under controlled environment. The results indicate that the HVS system can quantify leak rates between 108 and 3,254 g/h with a maximum uncertainty of 10% as long as the distance between the leak source and the HVS system sampling port is maintained at less than 50 mm. In future work, the HVS system will be used to characterize methane emissions from LNG offloading or bunkering process, and update the GHG inventories in North America to fill the knowledge gap in the complete lifecycle analysis of LNG fuel for heavy-duty vehicles and marine vessels.
