CH₄ Methane Slip

Unburned methane passing through LNG-fuelled engines. Methane has ~28× the 100-year warming potential of CO₂, so slip can erode the climate advantage of LNG substantially.

PollutantsLNG

Engine cycleAverage engine powerkWAnnual operating hourshCH₄ slip overrideg/kWhDefaults from Fourth IMO GHG Study: 5.5 for Otto MS, 2.5 for Otto SS, 0.2 for Diesel cycle.

Annual CH₄: 264.00t

CO₂-equivalent (GWP100=28): 7,392t CO₂e

CO₂-equivalent (GWP20=82.5): 21,780t CO₂e

20-yr horizon - IPCC AR6

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

m_{\text{CH}_4} = \frac{P \cdot h \cdot S_\text{cycle}}{10^6}

Symbol	Meaning	Unit
$m_{\text{CH}_4}$	Annual methane mass	t
$P$	Average engine power	kW
$h$	Annual operating hours	h
$S_\text{cycle}$	Slip rate by engine cycle	g/kWh
$GWP$	28 (100 yr) or 82.5 (20 yr)

Source: Fourth IMO GHG Study 2020; IPCC AR6 - methane GWP

In short

Estimate methane slip from LNG-fuelled marine engines and convert to CO₂-equivalent using GWP100 and GWP20.

Learn the theory Engine Performance Monitoring: PMI Systems