> ## Documentation Index
> Fetch the complete documentation index at: https://docs.appliedaifoundation.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Reefer correction

> How reefer-container CO₂ is stripped from CII per IMO MEPC.355(78).

Container ships and reefer vessels carrying refrigerated containers consume extra fuel to keep cargo cold. IMO MEPC.355(78) recognises this is **cargo-related** rather than propulsion-related, and lets operators strip those emissions from the Attained CII calculation.

## Formula

```
Reefer fuel (tonnes) = Cx × SFOC × Reefer-Hours / 1,000,000
Reefer CO₂ (tonnes)  = Reefer fuel × CF
Corrected Attained CII = (Total CO₂ − Reefer CO₂) × 10⁶ / (Capacity × Distance NM)
```

## IMO default constants

The platform uses the MEPC.355(78) defaults:

| Constant                  | Value                | Notes                       |
| ------------------------- | -------------------- | --------------------------- |
| Cx (default reefer power) | 2.75 kW              | Per active reefer           |
| SFOC (2-stroke engines)   | 175 g/kWh            | Default for container ships |
| SFOC (4-stroke engines)   | 200 g/kWh            | Alternate, configurable     |
| CF (HFO)                  | 3.114 t CO₂ / t fuel | Default                     |
| CF (MGO/MDO)              | 3.206 t CO₂ / t fuel | Alternative                 |

## Inputs from the consumption log

The platform sums `activeReefers × period` across every report in the year to compute total **reefer-hours**. From there, fuel and CO₂ follow directly.

## What you see

On the vessel detail page, two CII numbers are shown side by side:

* **Database CII** — what's reported in the consumption logs (operator-supplied, may or may not include reefer correction depending on source)
* **Corrected CII** — the reefer-corrected figure computed by the platform

A link opens the full MEPC.355(78) PDF in an in-app slide-out for reference.

## Implementation

`src/lib/utils/ciiCalculator.ts` — exports `calculateReeferCorrection` and `calculateCIIWithReeferCorrection`.

## Reference

* [IMO MEPC.355(78)](https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MEPCDocuments/MEPC.355\(78\).pdf) — 2022 Interim Guidelines on correction factors and voyage adjustments for CII calculations
* [IMO MEPC.364(79)](https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MEPCDocuments/MEPC.364\(79\).pdf) — CO₂ emission factors (Cf) for HFO and MGO