Catastrophic consequences

A new study shows that the scale and impact of marine lubricant operational discharges in port waters around the world is worse than previously thought, writes Dr Dagmar Schmidt Etkin

Maintaining water quality in ports and harbours around the world is of growing importance, driven by new legislation such as the National Pollutant Discharge Elimination System of the Clean Water Act in the United States and the European Union’s Marine Strategy Framework Directive. While monitoring of land-based pollution is increasingly routine and preparedness for serious spills of oil cargo is commonplace, awareness of operational discharges of mineral oils has until recently been patchy. But according to a recent study by Environmental Research Consulting (ERC), these discharges may be significant in terms of their quantity and their environmental impact.

The UN Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP), administered by the IMO, estimates there are 645,000 tonnes of annual anthropogenic oil inputs into the marine environment. ERC’s study indicates that on top of that amount, there are an additional 10% from marine lubricant operational discharges – or 61,000 tonnes entering port waters worldwide, or one and a half times the amount spilled in the 1989 Exxon Valdez disaster.

While operational lubricant discharges are smaller-scale than large spills, their chronic and widespread occurrence is causing significant environmental impacts. Conventional lubricant blends are relatively persistent, do not evaporate nor disperse into the water column. The mixture of crude oil base stocks and up to 30% performance-enhancing additives, which can include heavy metals, forms a persistent, bioaccumulative and toxic chemical, the effects of which can impact marine ecosystems at all levels and result in chemicals working their way through the food chain up to humans.

Spillage of lubricants is the more visible problem. Due to the volume of marine lubricating oil in use, these are relatively frequent. According to US port spills data, almost half of these spills occur during dockside operations, with incidents also regularly occurring during bunkering operations, repair and maintenance and bilge pumping.

By extrapolating the US spillage data to the world’s 4,708 ports and harbours, ERC estimates that in total almost a million litres of lubricants spill into port waters each year. Of the world’s ports, Istanbul was found to be the most affected, while the UK is the most affected country. These spillage figures are very conservative, considering high US vessel standards and spill prevention measures compared with other parts of the world. At the same time, since spills most often involve relatively large volumes and produce a surface sheen, they also tend to attract the attention of authorities – who can respond to the problem effectively.

Operational discharges of lubricants represent an entirely different challenge. It was in 2001 that a study commissioned by the European Commission first identified the stern tube as a significant contributor of day-to-day oil loss from ships, and the issue has since been of growing interest to regulators and shippers interested in protecting the environment.

Generally, stern tube shaft seals are the only barrier between the oil in the stern tube and the sea. A propeller shaft sealing system aims to prevent the entry of water into the stern tube where it could damage the bearings, and lubricant leakage into the sea in the opposite direction. But over time, the seals become damaged and worn, allowing stern tube oils to seep directly into the sea. Levels of lubricant loss via stern tubes have been the subject of speculation for many years, but by analysing consumption data for different vessel classes, ERC was able, for the first time, to reliably estimate lubricant inputs into the marine environment.

According to ERC research, stern tube emissions vary widely depending on the vessel type, from as high as 20 litres per day for barge carriers and 11 litres per day for IWW oil tankers to one litre per day for bulk carriers and less for smaller vessels. The average for all vessel types is 2.6 litres – less than the maximum allowable leakage for vessels of at least 1,000dwt, approved by Lloyd’s Registry Class Society Seal Type Approvals, at six litres per day. While the IMO Marine Environmental Protection Committee (MEPC) has considered figures of as much as 80m litres of stern tube oil entering marine waters annually, and there are significant challenges to estimating any form of sub-sea pollution, ERC found a range of between 4.6m and 28.6m litres entering port and harbour waters from stern tube leakage alone each year.

The more ground-breaking discovery was perhaps the scale of other low-level operational discharges. Some of these come from on-deck machinery, from which ERC considered an average 10% spilled on deck would enter the sea via run-off or during deck washing. The research found hydraulic systems, which use large amounts of lubricants at high pressure, to be the most important top-side sources of lubricant loss.

Below the waterline, various ship machinery also causes invisible discharges directly into port waters, with stern, bow, and controllable pitch propeller hydraulic thrusters the most important sources. Here ERC’s research found that together, on-deck and sub-sea machinery result in the release of 32.3m litres of oil into the sea during normal ship operations. This figure excludes discharges from the hydraulic systems of land-based cranes, which use similar lubricating oils – which should also be of interest to port and terminal operators.

The port most affected by operational lubricant discharges is Singapore followed by Istanbul, Gibraltar, and Brunsbuttel – the gateway to the European river and canal system – while the most affected countries as a whole are Japan, China, the UK, Turkey and the US.

What does this mean for the industry? Certainly it is a challenge that faces multiple organisations – shippers, ports, and environmental agencies. What is important is that it is now clear that lubricant pollution is a problem that needs addressing. While debate is necessary on responsibilities and solutions, it is clear that both ports and terminal operators should, and are in a position to, take a lead. The Swedish Clean Shipping Index project being developed at the port of Gothenburg, offers two examples of how this can be done. The Index is aimed at informing importers and exporters about various environmental investments on ships, with the aim of reducing greenhouse gases and pollution. Technologies considered include water-separated stern tubes, which do not use any stern tube oil, and environmentally responsible lubricants, which are biodegradable and less toxic than conventional lubricants.

Another opportunity for ports is more frequent checks on machinery and vessels to ensure early replacement of faulty equipment, as well as training of vessel personnel in better maintenance and operational procedures. Finally, investment in environmentally responsible lubricants for the port or terminal’s own vessels and cranes could send a signal to customers to follow suit.

The issue is an important one – and not least financially. In the waters around the port of Rotterdam, ERC estimated one million litres of lubricating oil are spilled or discharged each year – contributing to estimated cleanup costs of US$9m-12m for Dutch ports from lubricant pollution alone. So it is already in the interests of port authorities – as well as local conservationists and the fishing and tourism industries – to take action.