THE UNDERWATER IMPACT

The onus on shipping companies to reduce sulphur emissions has historically been lax. Cheap – but sulphur-rich – fuel, and a conundrum over whose responsibility falls where when vessels enter international territory, has made emissions-monitoring tricky. But last year new global limits on ships’ emissions in and around ports were introduced to tackle air pollution.

A team of Southampton researchers is part of a Europe-wide project to assess whether measures being taken by shipping companies to cut air pollution are working – both above and below water.

The €8 million EMERGE (Evaluation, Control and Mitigation of the Environmental Impacts of Shipping Emissions) project is evaluating the effects of potential emission reduction solutions for shipping in Europe.

As part of EMERGE, the team of environmental experts from Southampton, in partnership with a team from the University of Hertfordshire, is taking a close look at so-called ‘scrubber technology’. This is a method many cruise ships, tankers and larger marine vessels use to remove pollutants from the gases passing from their engines up exhaust funnels and into the air. the contaminants that would have been emitted into the air – is usually released into the sea. There is a big question mark over the impact this is having on delicate marine ecosystems. The Southampton researchers are recruiting a small team of sea urchins and mussels to find out.

Ian Williams, Professor of Applied Environmental Science, and Malcolm Hudson, Associate Professor in Environmental Sciences, are leading Southampton’s involvement, working with Research Fellow Lina Zapata Restrepo, data scientist and spatial analyst Patrick Osborne, and a small team of Master’s students.

Ian said: “It’s not widely known among the public that aviation and shipping emissions have historically been routinely excluded from all kinds of databases that capture emissions. This is because any emissions that occur outside national borders are deemed to have occurred in international territory and nobody wants to take responsibility. The reality is that the total emissions we produce globally are hugely underestimated.”

Large vessels use bunker fuel. “This is the gloopy, heavily-contaminated black sludge that is left when everything else – propane, butane, diesel, gasoline, even bitumen – has been taken out of the crude oil,” explained Ian. “Bunker fuel is full of sulphur and heavy metals, but it’s used for good reasons – it’s an effective use of material that would otherwise be waste, and it’s cheap.”

Pollution problem

Sulphur emissions at sea is one of the last remaining sulphur pollution problems to be tackled.

Ian said: “Sulphur dioxide from fossil fuels on land was a terrible problem in the ‘60s, ‘70s and ‘80s, but we have addressed that by removing the sulphur from fuel. In the ‘70s, electricity generation from fossil fuels was legislated against, then in the ‘80s and ‘90s cars were addressed by removing lead from petrol and fitting catalytic converters. It’s taken 30 more years to address shipping, partly because of the lack of alternatives. The last remaining area where sulphur emissions are a problem is out at sea.”

This is now being forced to change. From 1 January 2020, a new limit was imposed regarding sulphur dioxide and nitrogen oxide emissions close to port areas, known as Sulphur Emission Control Areas. The new global upper limit on the sulphur content of ships’ fuel has been reduced from 3.5 per cent to 0.5 per cent.

“The legislation has focused on sulphur dioxide emissions because they are harmful to human health and they contribute to acid rain,” explained Malcolm. “Ships have been ordered to reduce their sulphur emissions and they have two ways of doing this – they can either use much more expensive fuel, which most can’t afford to do, or they can put in scrubber technology.”

Scrubber technology diverts pollution into the sea, instead of into the air.

Ian said: “Effectively, one problem has been solved, but it has potentially created another – pumping the sulphur dioxide into the sea water rather than the air. The theory is that the ocean is big enough to handle it, and it sings to the old adage ‘the solution to pollution is dilution’.”

“In open water, that’s perhaps true,” added Malcolm. “But in a harbour that’s enclosed you are potentially going to get a build-up of contaminants.”

Sea urchins and mussels

The team will be assessing the impacts of the scrubber emissions on marine life in the Solent, using the experimental aquarium at the National Oceanography Centre (NOC). Sea urchins and mussels will be used to find out the potential implications on the marine ecosystem.

Malcolm explained: “We’re focusing on sea urchins and mussels because they are widespread and are important parts of the ecosystem, but they are also sensitive to pollution. Mussels are filter-feeders – they feed on plankton and other microscopic sea creatures, filtering the water. Sea urchins are grazers and help control algae.

“We’ll be looking to find out whether exposure to concentrations of sulphur they could encounter from the discharges from ships reduces their reproductive capacity or is harmful to their lifespan. That will give us a good insight into the potential wider impact of sulphur pollution on the ecosystem.”

The toxicological trials on the marine animals will start this summer. Specimens of sea urchins have been collected from the south west, where they are prevalent. Mussels will be collected from the dockside adjacent to NOC.

Alongside this work, Ranjeet Sokhi, Professor of Atmospheric Physics at the University of Hertfordshire, is leading a team of researchers who will be modelling the air pollution. “The intention and the hope is that the introduction of the scrubber technology will reduce emissions from ships and that will improve the air quality for the population of Southampton,” said Malcolm.

Dr Malcolm Hudson holding a sea urchin

The big picture

The studies in Southampton are running in parallel to studies in ecologically vulnerable locations across Europe, including The Venice Lagoon, Piraeus and the Eastern Mediterranean, the Aveiro Region of Portugal, and the Oresund Strait between Sweden and Denmark.

Ian concluded: “We genuinely do not know if the scrubbers are having a beneficial effect. The water quality in and around marinas is worse than in the Solent itself, and that pollution is from recreational vessels and not liners. But whatever our research establishes, we’ll be providing an early warning of what might happen.”

EMERGE is a four-year project, which started in February 2020 and is funded by Horizon 2020.