Methane slip measurements are crucial for reducing greenhouse gas emissions reported by maritime vessels. As liquefied natural gas (LNG) gains importance in the global fuel mix, incomplete combustion in current engines results in the release of unburnt methane into the atmosphere. Methane is significantly more potent in terms of global warming potential, being over 25 times stronger than carbon dioxide (CO2).
This makes understanding and managing methane slip essential for minimizing a vessel’s greenhouse gas (GHG) footprint. The regulatory landscape, shaped by EU regulations and IMO guidelines, addresses methane slip from LNG-fueled engines by employing standard factors. These standard correction factors can sometimes lead to methane slip contributing up to 24% of reported GHG emissions, expressed in CO2 equivalent, based on methane’s GWP of 28.
Regulations allow for alternative reporting methods if direct emissions measurements can be certified. In January 2025, the IMO Correspondence Group took steps toward standardizing quantification, proposing guidelines for direct methane emissions measurement from marine diesel engines. DNV anticipates these draft guidelines will gain acceptance at the upcoming MEPC 83 meeting on April 11, 2025.
To further support this transition, DNV’s accredited emissions laboratory, Envilab, offers precise methane slip measurement services that adhere to the new IMO draft guidelines. Our services are available for both test beds and onboard vessels, resulting in official emissions reports that certify reduced methane slip factors. Direct methane slip measurements provide essential benefits, especially if standardized factors appear inflated for specific engine types or if methane abatement technologies are in place.
While methane slip may initially seem minor, it can greatly influence reported GHG emissions due to methane’s high GWP. Accurate measurement allows for potential benefits comparable to energy-saving initiatives and ensures that the GHG equivalent emissions related to methane can be significantly reduced through the application of methane catalysts. It is advisable for maritime stakeholders to assess the relevance of standard methane slip factors compared to their engines.
Collaborating with engine designers can help identify strategies for mitigation. DNV extends support for the necessary measurements to facilitate these assessments.