Image caption, Rotterdam is home to five oil refineries ByAnna HolliganReporting fromRotterdam, Netherlands Published 15 minutes ago Standing on a grassy verge in the Hook of Holland, I'm overlooking the Port of Rotterdam.
At the delta of the Rhine and Meuse in the Netherlands, on land largely reclaimed from the North Sea, it's the biggest port for freight, external in Europe.
By some measures, Rotterdam alone handles almost as much cargo as all UK ports combined.
The horizon is dominated by cranes, bulk carriers and container stacks – the visible parts of a vast energy and chemicals hub.
Five refineries, including Shell's largest in Europe, process hundreds of thousands of barrels of crude oil a day, while a tight cluster of chemical plants feeds factories across the continent.
According to research by CE Delft, the fossil fuels flowing through the port are ultimately linked to around 600 megatonnes of CO2 a year – many times more than the CO2 output of the Netherlands' biggest airport, Schiphol.
That scale has made Rotterdam a test case for a difficult question: can a port built on fossil fuels ever truly become green?
Pressure is building on the port to do something.
A lawsuit brought by environmental group Advocates for the Future argues that the Port of Rotterdam Authority is not doing enough to phase out fossil-based energy, and wants a concrete plan to wind down the coal, oil and gas flows whose emissions dwarf those of most countries.
Rotterdam's own industrial cluster currently emits about 29 million tonnes of CO2 a year – roughly half of the Netherlands' domestic emissions, says Mark van Dijk, head of external relations at the Port of Rotterdam Authority.
That's the equivalent of tens of thousands of return flights from Amsterdam to Los Angeles.
"It's not good," admits van Dijk.
Image source, Anna Holligan Image caption, The port has plans to cut the emissions of its own activities The Port Authority has a plan to cut the emissions of its own activities and encourage businesses on the site to be greener.
It has set targets to cut its own direct and purchased energy emissions by 90% between 2019 and 2030.
The plan includes developing a hydrogen hub where companies can test new fuels, investing in onshore power so ships can plug into the grid instead of burning fuel at berth, and supporting bunkering of alternatives such as LNG, biofuels and methanol.
There is also an effort to mitigate CO2 emissions.
"In the short term we're focusing on CCS [Carbon Capture and Storage] – capturing CO2 and storing it in depleted gas fields," van Dijk says, referring to the Porthos project that will pipe industrial emissions offshore.
Buffeted by the wind, Advocates for the Future director Maikel van Wissen argues that a port of this scale shouldn't just be managing the flow of fossil fuels.
Instead, he argues, it has a responsibility to use its clout to speed up the shift to cleaner operations.
"A state-owned enterprise should take legal obligations on states to reduce emissions," Van Wissen says.
"We are asking in the lawsuit to phase out that dependency, to create alternatives.
It takes time, but if you don't have a plan, you always choose cheap short-term solutions.
This is an important hub, if you do it in a controlled way, you offer an alternative, that will stop industry from moving elsewhere." Image source, Anna Holligan Image caption, Oscar van Veen is working on cutting emissions at the Port of Rotterdam The port says it is making efforts to shift its business model.
"We try to work together with the polluters, and slowly phase them out," says Oscar van Veen, director of innovation at the Port of Rotterdam, speaking on a small boat in the harbour.
He pauses, then corrects himself: "As fast as possible, of course." But many of the biggest emitters in the port answer to headquarters in the US or China.
Their loyalty lies with boardrooms abroad.
If the rules in Rotterdam become too tight, they can simply move – as Shell shifted its headquarters to the UK and Unilever left Rotterdam altogether.
"The Port of Rotterdam is a key player in this sustainable transition but their sphere of influence is limited," says Bettina Kampman, from environmental consultancy CE Delft, which works for governments, companies and NGOs.
Even transitioning their own activities to lower emissions comes with challenges.
"New developments need physical space.
They can speed up the energy infrastructure developments - the electricity needed to electrify the processes.
That's all limited at the moment due to the lack of power cables," Kampman says.
Emeritus professor Harry Geerlings, of Erasmus University Rotterdam, has spent more than three decades studying sustainable transport and ports.
He is sceptical that any single port authority can drive a full transition on its own.
What is needed, he says, is a global level playing field – the kind of framework provided in Europe by the Emissions Trading System and past rules on sulphur in marine fuels.
He points out how EU sulphur limits changed behaviour: ships calling at European ports had to switch to cleaner fuels or fit scrubbers to reduce pollution.
China initially resisted, he says, but when its ships could no longer enter US and European ports without complying, it followed suit.
"If you have the right incentives, you change the behaviour of these companies." But there are limits to what regional rules can do.
Many ships now sail with dual fuel set ups, burning cleaner, low-sulphur fuel as they enter European waters, then flipping back to cheaper, high sulphur heavy fuel oil once they are out on the high seas.
Geerlings believes Rotterdam's port authority genuinely wants to change and is building the infrastructure for a smoother transition.
"But their biggest income is still tied to fossil fuel industries," he notes.
"It's not simply a switch you turn on or off.
A port needs activity as a logistics node – otherwise it's no longer a port.
It's a real dilemma." Image source, Anna Holligan Image caption, Rotterdam handles almost as much cargo as UK ports combined The geopolitics are not always helpful.
Across the Atlantic, US President Donald Trump has cast doubt on climate policy and railed against wind power, while offering incentives that favour fossil fuels over renewables.
That contrast sharpens Rotterdam's concern about losing energy intensive industry to regions with looser rules and cheaper power.
Advocates for the Future argues that as a publicly owned company, the Port of Rotterdam Authority should be held to a higher standard.
It wants a detailed phase-out plan for fossil activities, not just a long-term promise of climate neutrality by 2050.
"We are not asking for anything extraordinary," says director Maikel van Wissen.
"We're asking for a plan that really contributes to a sustainable future for the port." "We do want the same thing," insists Van Dijk.
Sharing an electric taxi back towards the city, a 45-minute drive from the edge of the sprawling port.
He stresses that Rotterdam and its critics are, on paper at least, heading for the same destination: net zero around mid century.
The disagreement is over how fast, and how radically, to change.
