Ro-Ro Cargo Emissions & Retrofit Radar
Ships ranked by AER (Annual Efficiency Ratio) — grams of CO₂ emitted per tonne of deadweight carried one nautical mile (g CO₂/dwt·nm), the IMO carbon-intensity metric behind the CII rating — from official EU MRV emissions data for reporting year 2025. Lower is greener. Pick a segment and size class to see the greenest vessels first.
CII band distribution
47 at D/E173 rated vessels · 24 of the D/E set dock within 12 months
Docking pipeline — D/E vessels per quarter
Windows estimated from the class-expiry docking model, not bookings.
Top eligible retrofit measures for this segment
| Measure | Eligible | CO₂ reduction | Capex band | Payback | Confidence |
|---|---|---|---|---|---|
| Propeller redesign / replacement | 110 | 5–10% | €400k–1,200k | — | vendor claim |
| Turbocharger cut-out | 55 | 1–3% | €80k–250k | — | vendor claim |
Capex bands are indicative vendor/literature priors. Payback appears once price parameters are configured.
Retrofit opportunity in this segment
Retrofit prospects — worst band first
| Vessel | Band | Age | Drop year |
|---|---|---|---|
| STENA HIBERNIA · <25k | E | 30y | 2026 |
| EOS · <25k | E | 28y | 2026 |
| SARDINIA · <25k | E | 22y | 2026 |
| BRITANNIA SEAWAYS · <25k | E | 26y | 2026 |
| MAYAR · <25k | E | 25y | 2026 |
Why there is no AER ranking here
Under the IMO CII scheme, ro-ro cargos are measured against gross tonnage, not deadweight — so a DWT-based AER ranking would order these ships by the wrong emissions metric. Rather than publish a misleading table, we show the GT-based CII bands above, which are the correct comparison. The per-vessel emissions data remains available on each vessel page.
Which engines power the greenest fleets?
The main engine is the single largest CO₂ source on board — typically well over 80% of a ship's emissions come from propulsion. We aggregated this ranking the other way around: every engine design is scored by the measured carbon intensity of the vessels carrying it, licensee-built units merged under their design brand. The verdict from the 2025 data — modern dual-fuel designs like MAN B&W's ME-GI and WinGD's X-DF families, together with EGR/SCR-abated and ultra-long-stroke G-type engines, consistently power the most emission-friendly ships in service.
AER (Annual Efficiency Ratio) = annual CO₂ emissions ÷ (deadweight × distance sailed), the IMO carbon-intensity metric used for CII ratings. It is built only from measured CO₂, distance and deadweight — not the self-reported cargo transport-work figure, which is unreliable. Implausible outliers (top 2% per segment) are excluded. Grade A–E reflects each vessel's rank within its segment. Source: EMSA THETIS-MRV.