Ballast-Leg Correction
Many voyages are laden out, ballast back. This calculator computes the round-trip CO₂ intensity per tonne-nm of cargo delivered, which is usually a better comparator than a single-leg AER or EEOI.
Laden leg
Ballast leg
Fuel Cf
Round-trip CO₂
2,989.4t
Cargo-nm delivered
480,000,000t·nm
Round-trip EEOI
6.23g CO₂ / (t·nm)
Formula, assumptions, and limits
$$\text{EEOI}_\text{rt} = \frac{(F_\text{laden} + F_\text{ballast}) \cdot C_f \cdot 10^6}{m_\text{cargo} \cdot d_\text{laden}}$$
The ballast fuel is counted in the numerator because it exists only to reposition for the next laden leg. The denominator uses the laden distance and cargo mass only - ballast miles produce zero cargo work.
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