Policy approaches to mitigate in-use methane emissions from natural gas use as a marine fuel

Unregulated in-use methane emissions (or methane slip) can reduce or even eliminate the overall climate benefits of using liquefied natural gas as a marine fuel. We conduct critical review and expert interviews to identify methane slip mitigation measures, and then identify and evaluate potential policy instruments that could incentivize their uptake while considering the shipping sector's climate targets. We find that regulatory instruments are expected to perform the best across a range of criteria when they are at the global level, include methane on a CO2-equivalent and lifecycle basis, promote polycentric approaches to climate governance, and allow flexibility in how the industry incorporates decarbonization measures. Market-based approaches and informational governance policies complement regulatory instruments by improving cost-effectiveness and increasing the availability of relevant information on emissions mitigation. The urgency and scale of shipping climate targets underscore the need for policy approaches that support planning for long-term decarbonization pathways and that can avoid locking into fossil-carbon intensive systems.