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IMO - Review of Recent Well-To-Wake Greenhouse Gas Studies


Author: S. Hartman & M. Kofod, Shell Global Solutions Deutschland GmbH, Hamburg; T. Mundt & Christos Chryssakis, DNV GL, Hamburg & Høvik.

Date: July 18, 2014

Page Count: 17

From the Document:


Recently two studies were published analysing the Well-to-Wake (WtW) greenhouse gas savings by substituting conventional marine fuel by LNG. One of these studies focuses on LNG supply in the Netherlands (TNO) and the other on supply in the United States (ICCT). This document summarizes these two studies and the results are compared. Furthermore, certain aspects of WtW analyses are added that result in a more representative comparison of conventional marine fuels versus LNG. This concerns also the discussion about an appropriate reference case that includes the consequences of the IMO sulphur legislation.

The TNO study concluded that in general no WtW Greenhouse Gas (GHG) advantage should be expected for LNG; only in the case of very large container ships up to 20% GHG savings are possible. The ICCT study analyses different LNG supply pathways for the United States and find WtW GHG emission changes from +5% increase to -18% decrease if compared to a reference fuel depending on the origin of the natural gas, state of applied liquefaction technology and complexity of the distribution chain. Both studies do not include the impact of the IMO sulphur limits into the chosen reference case.

In view of the authors a thorough LNG WtW analysis should address more aspects. The two cited studies do not reflect the recent findings that methane leakage in natural gas production might be higher than expected. It is not known whether this will be reflected in the official WtW GHG data frameworks but it should be mentioned that this could impact the GHG balance for LNG negatively (leading to a loss of up to 6% on the GHG saving potential).

On the other side, the results of both studies would show higher GHG savings for LNG if recent improvements of marine natural gas engine efficiency and the technical potential for methane slip reduction were included. Assuming better LNG engine efficiency could have an impact of 4% to 6%, the prevention of methane slip changes the results by 20%.