When it comes to climate pollution, carbon dioxide usually takes center stage. But methane, the primary component of natural gas, is a much more potent greenhouse gas in the near term—about 80 times stronger than CO₂ over a 20-year period. That potency means even small leaks and inefficiencies can have outsized climate consequences.

One of the most overlooked sources of methane emissions is methane slip –  methane that escapes unburned from natural gas and LNG engines due to imperfect combustion. It’s a problem that undermines the climate case for natural gas and costs the industry real money in wasted product.

Methane Slip in Context

For shipping, trucking, and power generation companies investing in LNG as a “cleaner” alternative to oil, methane slip represents a climate credibility gap and a financial leakage problem. If a vessel loses 3–4% of its fuel as unburned methane, not only does its greenhouse footprint balloon, but the operator also wastes expensive fuel.

When it comes to methane slip, not all engines are created equal.

• Low-pressure, four-stroke “Otto” cycle LNG engines used in long-haul ocean vessels are the worst offenders, with slip rates documented at 3–4% of fuel under certain operating conditions. 

  
  

• Natural gas trucks and buses also emit tailpipe methane, undermining the well-to-wheel climate benefits of converting fleets to natural gas or LNG.

• Stationary gas engines that drive compressors and generators in oil and gas operations leak methane via exhaust slip as well, compounding upstream fugitive emissions from general leaks and releases.

Methane slip is wasteful and harmful wherever it happens. In the shipping industry, it’s likely to get more expensive. A draft policy from the International Maritime Organization (IMO) will begin charging a per-CO₂e fee for methane slip from large ships (over 5,000 gross tonnage).  Estimates suggest that fees could exceed $300 billion by 2035 if the fleet misses targets, and some firms could face penalties up to $1,200 per tonne of bunker fuel emitted above stated targets. IMO’s policy has been held up by politics, but experts are confident the fees are a delayed eventuality.

Current Approaches to Slip Reduction

Industry and researchers are working on solutions. For example, better engines and better load and route strategies can significantly reduce the amount of unburned methane emitted in exhaust streams. Methane oxidation catalysts added to existing systems can break down slip in exhaust from lean-burn engines. Others are exploring how system design changes can optimize ignition or increase combustion efficiency.

These measures matter. They save fuel, reduce operating costs, and help companies avoid new fees from tightening environmental rules from the IMO and national regulators. But none of them completely eliminates methane molecules from exhaust streams. Even the best engine designs leave a residual slip that still matters for the climate.

Bennu Removes What’s Left

That’s where Bennu comes in. Our technology completely and permanently eliminates fugitive methane emissions and methane slip from exhaust streams. It’s a cost-effective solution for various industries, but it’s particularly well-suited for shipping, where, for some routes, methane slip is about to become significantly more expensive.

That’s why we’re testing and refining it on the ocean. Right now, we’re installed in general locations on a cargo vessel. But with slight design adjustments, it can be installed directly in-line with existing exhaust streams, ensuring that every molecule of methane that would otherwise escape into the atmosphere is eliminated before it leaves the stack.

Bennu is a perfect complement to other efforts aimed at reducing methane slip in the first place. Those efforts will save fuel, reduce costs, and help industry move toward a much lower-carbon system. And Bennu takes care of the rest. 

Methane slip is a climate and cost blind spot hiding in plain sight. It erodes the case for LNG, wastes valuable fuel, and exposes companies to regulatory and reputational risk. Incremental measures can reduce slip, but to close the gap entirely, the industry needs solutions that leave zero methane behind.

Bennu offers that solution. By permanently eliminating methane from exhaust, we help long-haul shipping deliver on its climate promise—with low costs and no compromises.