A large container vessel idling at anchor burns roughly four tonnes of fuel an hour and puts about twelve tonnes of CO₂ into the air for it. For decades that was somebody else’s externality. Under EU ETS, it is now a line on an invoice.
Waiting at anchor used to be free. A vessel arrived early, dropped the hook, and burned bunker fuel to keep auxiliaries running and hold position until a berth opened. The fuel cost money, but the carbon cost nothing. That asymmetry shaped how the whole industry scheduled itself: arrive as fast as possible, then wait. First come, first served — and first to burn.
Carbon pricing breaks the logic. Since 2024, shipping sits inside the EU Emissions Trading System, and every tonne of CO₂ emitted on voyages touching the EU must be surrendered as an allowance. At allowance prices in the tens of euros per tonne, a single long voyage can carry a six-figure ETS bill. The hours a vessel spends idling at anchor are no longer a rounding error — they are a metered, reported, billable cost.
Waiting time was always expensive. Now it is also itemised.
Where the twelve tonnes come from
The arithmetic is unforgiving. Heavy fuel oil releases a little over three tonnes of CO₂ for every tonne burned. A vessel holding station at anchor draws on the order of four tonnes of fuel an hour for its engines and auxiliaries. Multiply through and each idle hour is roughly twelve tonnes of carbon dioxide — before anyone has moved a single box.
Stack those hours across a congested gateway and the numbers climb fast. A queue of vessels waiting a day or more, repeated across hundreds of port calls a year, is a continuous plume of avoidable emissions that now maps directly onto allowance purchases.
Just-in-time is the cheapest lever there is
The fix is not a new fuel or a retrofit. It is timing. If a vessel knows when its berth will genuinely be ready, it can slow-steam across the last leg and arrive to work immediately, rather than sprinting to the anchorage and burning fuel to wait. Industry just-in-time trials have shown emissions reductions on the order of fourteen percent on the approach leg — and a single coordinated call at Algeciras was measured to avoid roughly thirty-three tonnes of CO₂.
No capital project comes close to that cost-per-tonne. The savings come from information, not steel.
What Saagar does about it
Just-in-time only works if the arrival time is honest. That means binding the vessel’s schedule to what is actually happening on the quay:
- Saagar-Berth predicts realistic berth readiness from live yard and gate ground-truth, then computes the most efficient queue across tide, draft, berth fit, labour and demurrage — so the recommended arrival time is one the port can actually keep.
- Saagar-Insight turns the resulting port-call events into EU ETS, FuelEU Maritime and IMO CII records and MRV-aligned exports, for both the port and the carrier, so the saving is not only realised but documented.
The result is a loop: better coordination cuts the fuel and carbon that drive the bills, and the same events that prove the saving also file the compliance. The twelve-tonne hour stops being invisible — and then stops happening.
Sources: EU ETS maritime scope (in force 2024); IMO and DCSA Just-in-Time Arrival guidance; Port of Algeciras JIT trial reporting. Fuel and emission figures are order-of-magnitude estimates for illustration.