LNG Supply Chains: A Supplier-Specific Life-Cycle Assessment for Improved Emission Accounting

Abstract

Global trade in liquefied natural gas (LNG) is growing significantly, as is interest in the life-cycle greenhouse gas (GHG) emissions associated with LNG. Most assessments of lifecycle GHG emissions from LNG have employed national or regional average emission estimates; however, there is significant variability in emissions across different suppliers and across the natural gas supply chain. This work describes a framework for compiling supplier-specific GHG emission data for LNG, from the producing well to regasification at the destination port. A case study is presented for Cheniere Energy's Sabine Pass Liquefaction (SPL) LNG supply chain from production in the United States and delivered to China. GHG emission intensities are estimated to be 30−43% lower than other analyses employing national or regional average emission profiles. The segments driving these differences are gas production and gathering, transmission, and ocean transport. Extending the boundaries of this analysis to the power plant illustrates the effect of fuel switching from coal to natural gas; the effect of fuel switching in China is a 47−57% reduction in GHG emission intensity, cradle through power generation. This work highlights the important role customized life-cycle assessments can play to improve GHG emission estimates and differentiate supply chains to inform business and policy decisions related to the transition to a low carbon future.

Total Methane and CO2 Emissions from Liquefied Natural Gas Carrier Ships: The First Primary Measurements

“…To understand the GHG results in context, this study is compared to three recent desk-based studies, Roman-White et al, 7 NETL, 17 and thinkstep, 18 as shown in Figure 4 . All studies assess the life cycle GHG emissions associated with exporting LNG to different locations and included the LNG shipping transport as one part of the supply chain.…”

“… Comparison of GHG emissions from LNG shipping with other studies, expressed in kg CO 2equiv /t LNG delivered, using both GWP100 and GWP20 climate metrics for methane. Source: refs ( 7 )( 17 ), and ( 18 ). …”

“…The comparison with other studies has several limitations in terms of comparing “like-for-like”, primarily relating to transport distances and the propulsion technology. Similar distances (within 1000 km) were used, but only the Roman-White study 7 used a comparable propulsion technology. Note that no other study explicitly modeled generator engine emissions, only the main propulsion or an aggregate (e.g., based on the total fuel consumption as per ref 7 ).…”

“…Similar distances (within 1000 km) were used, but only the Roman-White study 7 used a comparable propulsion technology. Note that no other study explicitly modeled generator engine emissions, only the main propulsion or an aggregate (e.g., based on the total fuel consumption as per ref 7 ). Studies also typically have not included emissions from venting or fugitives.…”

“… 3 Both methane and CO 2 emissions have been found to be highly variable, 4 particularly across supply chain stages, 5 regions, 6 and operators. 7 However, there remains substantial gaps in our understanding of methane emissions from many regions and particularly relating to liquefied natural gas (LNG) transport.…”