> ## 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.

# FuelEU WtW

> Well-to-Wake intensity formulas, Annex II default factors, methane slip, and biofuel period dating.

`src/lib/utils/fuelEUCalculator.ts` implements EU Regulation 2023/1805 with Annex II default emission factors. This page documents the formulas and constants in use.

## WtW = WtT + TtW

```
WtT (per fuel) = Annex II default value (gCO₂eq/MJ)
TtW (per gram of fuel) = ttW_CO₂ × GWP_CO₂ + ttW_CH₄ × GWP_CH₄ + ttW_N₂O × GWP_N₂O
TtW (per MJ)   = TtW per gram / LCV (MJ/g)
WtW            = WtT + TtW per MJ (gCO₂eq/MJ)
```

Global warming potentials use **AR5** values:

| Gas | GWP |
| --- | --- |
| CO₂ | 1   |
| CH₄ | 28  |
| N₂O | 265 |

## Annex II default factors

The platform supports 19 fuel types. Key conventional and alternative fuels:

| Fuel              | LCV (MJ/g) | WtT (gCO₂eq/MJ) | TtW CO₂ (g/g) | TtW CH₄ (g/g) | TtW N₂O (g/g) |
| ----------------- | ---------- | --------------- | ------------- | ------------- | ------------- |
| HFO               | 0.0405     | 13.5            | 3.114         | 0.00005       | 0.00018       |
| LFO               | 0.0410     | 13.2            | 3.151         | 0.00005       | 0.00018       |
| MDO               | 0.0427     | 14.4            | 3.206         | 0.00006       | 0.00018       |
| MGO               | 0.0427     | 14.4            | 3.206         | 0.00006       | 0.00018       |
| LNG (Otto MS)     | 0.0491     | 18.5            | 2.750         | 0.031         | 0.00011       |
| Methanol (fossil) | 0.0199     | 31.3            | 1.375         | 0.00012       | 0.00002       |
| LPG (Propane)     | 0.0461     | 7.5             | 3.030         | 0.00005       | 0.00018       |
| LPG (Butane)      | 0.0455     | 8.4             | 3.030         | 0.00005       | 0.00018       |

Biofuels (TtW CO₂ counted as 0 — biogenic):

| Fuel         | LCV    | WtT  | Notes                             |
| ------------ | ------ | ---- | --------------------------------- |
| FAME         | 0.037  | 21.0 | Average across feedstocks         |
| HVO          | 0.044  | 10.0 | Certified sustainable             |
| Bio-Methanol | 0.0199 | 7.6  | Waste-based pathway               |
| Bio-LNG      | 0.0491 | 7.5  | Waste/manure                      |
| Bio-Blend    | 0.040  | 18.0 | Blended; partial biogenic content |

E-fuels:

| Fuel               | LCV    | WtT |
| ------------------ | ------ | --- |
| E-Methanol (Green) | 0.0199 | 3.0 |
| E-LNG              | 0.0491 | 5.0 |

Ammonia and Hydrogen:

| Fuel             | LCV    | WtT   | TtW N₂O |
| ---------------- | ------ | ----- | ------- |
| Ammonia (Grey)   | 0.0186 | 121.0 | 0.008   |
| Ammonia (Green)  | 0.0186 | 5.0   | 0.008   |
| Hydrogen (Grey)  | 0.120  | 132.0 | —       |
| Hydrogen (Green) | 0.120  | 5.0   | —       |

## LNG methane slip

For LNG and Bio-LNG, methane slip (`ttW_CH₄`) varies by engine:

| Engine                          | Slip (Cslip)   |
| ------------------------------- | -------------- |
| Otto medium-speed               | 3.1% (default) |
| Otto slow-speed                 | 1.7%           |
| Diesel                          | 0.2%           |
| LBSI (lean-burn spark-ignition) | 2.6%           |

The platform defaults to Otto medium-speed unless engine type is supplied.

## Biofuel period dating

Bio-Blend bunkers are dated against the user's certification records. Two periods exist with different certified WtW intensities:

| Period          | Cf (t CO₂ / t fuel) | WtW (gCO₂eq/MJ) |
| --------------- | ------------------- | --------------- |
| Pre-8-Aug-2025  | 2.331               | 9.2             |
| Post-8-Aug-2025 | 2.502               | 10.8            |

Cutoff: **8 August 2025** (FIFO consumption assumption). Consumption before the cutoff uses the earlier bunker; after, the later one.

## Fleet GHG intensity

```
Fleet GHG Intensity = Σ (Energy_i × WtW_i) / Σ Energy_i
```

Energy is computed per fuel as `tonnes × 1,000,000 × LCV`.

## Targets and compliance

```
Target intensity (year)  = step function from {2020 baseline, 2025, 2030, ..., 2050}
Compliance Balance       = (Target − Actual) × Total Energy   (in gCO₂eq)
Compliance status        = COMPLIANT if Actual ≤ Target else NON_COMPLIANT
Penalty (€)              = |Balance| / Actual × (€2,400 / 41,000 MJ)
```

The penalty divides by Actual to convert the gCO₂eq gap into MJ of energy at the actual intensity, then values that energy at €2,400 per tonne of VLSFO equivalent (41,000 MJ).

Targets are step-wise: the 2025 target (89.34) applies through 2029, then drops at 2030. Years before 2025 use the baseline (91.16).

## Implementation

`src/lib/utils/fuelEUCalculator.ts` — exports include `calculateWtW`, `calculateFleetGHGIntensity`, `calculateFuelEUCompliance`, `calculateFuelEUComplianceWithBiofuelPeriods`, and the `FUEL_FACTORS`, `LNG_CSLIP`, `GWP`, `GHG_TARGETS`, `BIOFUEL_EMISSION_FACTORS` constants.

## Reference

* [Regulation (EU) 2023/1805](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32023R1805) — FuelEU Maritime
* [Annex II default emission factors](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32023R1805#d1e32-94-1) — WtT, TtW, LCV for every supported fuel
* [IPCC AR5 GWP values](https://www.ipcc.ch/assessment-report/ar5/) — CH₄ = 28, N₂O = 265
* [DNV — FuelEU Maritime](https://www.dnv.com/maritime/insights/topics/fueleu-maritime/)
* [CE Delft technical report](https://cedelft.eu/publications/eu-ets-and-fueleu-maritime/)
* [Sustainable Ships — FuelEU penalty calculator](https://www.sustainableships.org/fueleu-maritime/)