Per-measure cost of CO₂ abatement in USD per tonne CO₂ avoided. The building block for a fleet-level MAC curve.
Formula
$$ \text{MAC} = \frac{\text{Capex}\text{annual} + \text{Opex}\text{extra} - F_\text{saved} \cdot P_\text{fuel}}{C_\text{avoided}} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $MAC$ | Marginal abatement cost | USD / t CO₂ | result |
| $\text{Capex}_\text{annual}$ | Annualised capital cost (loan + depreciation) | USD / year | finance model |
| $\text{Opex}_\text{extra}$ | Incremental annual operating expense | USD / year | engineering estimate |
| $F_\text{saved}$ | Fuel saved by the measure | t / year | engineering estimate |
| $P_\text{fuel}$ | Bunker price | USD / t | bunker index |
| $C_\text{avoided}$ | CO₂ avoided | t / year | $F_\text{saved} \cdot C_f$ or direct |
A negative MAC is a “no-regret” measure - saves money and CO₂. A positive MAC below the prevailing carbon price is still economic. Ranking ascending gives the optimal abatement sequence at a target CO₂ reduction.
Sources
- DNV - Maritime Forecast / Pathways to zero-carbon shipping.
- IMO MEPC.80/7/8 - IMO GHG strategy levers.