Formula
$$ m_{\text{CH}4} = \frac{P \cdot h \cdot S\text{cycle}}{10^6} $$
$$ m_{\text{CO}2e} = m{\text{CH}_4} \cdot \text{GWP} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $m_{\text{CH}_4}$ | Annual methane mass | t | result |
| $P$ | Average engine power | kW | operating data |
| $h$ | Annual operating hours | h | operating data |
| $S_\text{cycle}$ | Slip rate by engine cycle | g/kWh | Fourth IMO GHG Study 2020 |
| $GWP$ | 28 (100 yr) or 82.5 (20 yr) | - | IPCC AR6 |
Slip defaults
| Cycle | $S_\text{cycle}$ (g/kWh) |
|---|---|
| LNG Otto medium-speed 4-stroke | 5.5 |
| LNG Otto slow-speed 2-stroke LP | 2.5 |
| LNG Diesel high-pressure 2-stroke | 0.2 |
Sources
- Fourth IMO GHG Study 2020.
- IPCC AR6 - methane GWP.