UNDERSTANDING METHANE SLIP IN THE MARITIME INDUSTRY

The maritime industry is at a critical juncture in its journey towards decarbonization. While liquefied natural gas (LNG) has emerged as a promising solution for reducing greenhouse gas emissions, an often-overlooked issue, known as "methane slip," raises concerns among proponents and opponents alike. In the article, we found on SAFETY4SEA, the concept of methane slip and its significance in the context of maritime sustainability is well explained.

What is a "Methane Slip"?

In the ongoing discussions about greenhouse gas emissions in shipping, much attention has been directed towards carbon dioxide (CO2). However, it's essential to recognize that methane, another potent greenhouse gas, plays a significant role in global climate change. Methane is approximately 80 times more effective at trapping heat than CO2, emphasizing the urgency of addressing its reduction.

Methane Emissions in Numbers:

·     In 2018, methane contributed to 17.3% of the world's total emissions.

·     In 2020, methane (CH4) accounted for approximately 11% of all U.S. greenhouse gas emissions, including leaks from natural gas systems.

·     Greenhouse gas emissions, comprising CO2, methane, and nitrous oxide, in the total shipping industry, have risen from 977 million tonnes in 2012 to 1,076 million tonnes in 2018, as per IMO data.

Understanding Methane Slip

The term "methane slip" refers to the unintended release of methane during the combustion of natural gas in ship engines. While equipment designed to use natural gas as fuel typically achieves combustion efficiency of at least 98%, the remaining 2% of methane is emitted unburned, contributing to methane slip.

In simpler terms, methane slip represents unburned fuel that escapes ships' engines. Although it usually accounts for a small percentage of the overall fuel used, in operations with high energy consumption, it can become a significant source of emissions.

Causes of Methane Slip

Several factors influence methane slip, including engine type, duty cycle, speed, load, and the type of fuel used. According to Stamatis Fradelos from DNV Hellas S.A., methane slip occurs primarily due to:

·     Dead volume in the form of crevices between cylinder unit components.

·     Incomplete combustion, particularly quenching at the coldest part of the combustion chamber when running lean.

·     Due to leakage through piston rings or because of inadequate combustion, leading to the emission of unburned gas from the engine.

The Debate Surrounding LNG as a Marine Fuel

LNG, with its mature technology, has gained traction as a marine fuel option that can kickstart the decarbonization journey in shipping. It offers a 23% reduction in greenhouse gas emissions compared to oil-based marine fuels. However, the presence of methane emissions has fueled criticism of LNG as a shipping fuel.

Critics argue that the emissions reductions claimed for LNG primarily apply to two-stroke, high-pressure engines. They contend that methane emissions from LNG-fueled vessels could be on par with those from conventionally fueled ships. This debate underscores the need to address methane emissions associated with LNG.

Latest Developments: The Challenge of Methane Slip

In recent developments, the lobby group Transport & Environment conducted an investigation in Europe's largest port, the Port of Rotterdam, revealing significant unburned methane emissions on a ship. Approximately 80% of Europe's LNG used in shipping today is identified as worse for the climate than the fuels they replace due to the release of methane, a potent greenhouse gas.

Despite these findings, regulatory requirements to mitigate methane slip have not yet been imposed on operators or manufacturers. However, the maritime industry can take steps to prevent this.

Preventing Methane Slip

To reduce methane slip when natural gas must be used as a fuel, improving combustion engine efficiency is crucial. Engine manufacturers are actively promoting advanced engine designs that aim to minimize methane slip. This can be achieved through the integration of advanced technologies like exhaust gas recirculation or engine redesigns for improved environmental performance.

In the short term, operators can mitigate LNG-related issues through process and technology improvements. For instance, the use of fixed-arm connections during bunkering is more efficient than hoses, and capacity advancements can reduce leakage by reducing refueling frequency.

However, the overall low awareness of methane emissions and the absence of regulatory incentives have hindered progress in methane emissions reduction technologies within the shipping industry.

Understanding and addressing methane slip is mandatory in the maritime industry's journey toward sustainability and decarbonization. While LNG remains a promising marine fuel option, the industry must grapple with the challenge of methane emissions to fully realize its environmental benefits.

As discussions continue on reducing methane slip and enhancing environmental performance, it is essential for all stakeholders to stay informed and engaged in shaping a more sustainable future for maritime transportation. To read the original article and explore more maritime-related topics, visit SAFETY4SEA.

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