Typically, when one thinks of curbing harmful emissions, things like wind turbines, solar panels, and hybrid vehicles are first to come to mind. And this is not without due reason—power plants and automobiles are notorious for their consumption of fossil fuels, and efforts to make power generation and private transport “greener” have attained increasing public awareness and support. In August of 2012, the Environmental Protection Agency (EPA) famously issued a new set of corporate average fuel economy (CAFE) standards that automakers selling in the United States must meet by the year 2025, which would effectively double the miles per gallon (MPG) rating that new cars on the road in the US must achieve . In a similar vein, 2012 has been touted as “a bad year for the coal industry,” with 55 coal-burning power plants announcing their plans to close . By all appearances, things are headed in the right direction in terms of curbing climate change-inducing emissions.
Despite all this, there remains a major source of pollution that has largely escaped public scrutiny: cargo ships. Perhaps this is because the lack of day-to-day familiarity most people have with the shipping industry as compared to their more everyday experiences with filling up their car, paying their monthly electric bill, and so on. There are many fewer people who see the enormous ships firsthand than who benefit from the steady flow of goods they bring from overseas—clothing, meat, electronics, toys, and much more. Whatever the reason, maritime shipping has been and continues to be a significant and under-recognized source of pollution across the globe.
The primary cause for the increased level of pollution put out by these ships is their choice of fuel. There are a number of different grades of fuel oils that are used in these ships’ engines, categorized by their viscosities. The thinnest of these are comparable to what we know as diesel fuel on the common marketplace. However, the thickest of these, IFO 380 and LS 380, have a kinematic viscosity of up to 380 centipoises at 50 degrees centigrade—about five times the viscosity of corn oil at room temperature , . In fact, the fuel used on some of these big ships is so thick that it cannot even be pumped at room temperature—it needs to be heated to the boiling point of water before it can be piped into and used by the ships’ behemoth engines , . These thick “residual fuels” are what is left over after all the lighter fuels (e.g. gasoline and diesel) are removed from crude oil in a refinery—this fuel is the literal bottom of the barrel.
The greatest problem in using these thicker fuels comes from their increased sulfur content. IFO fuels of varying viscosities are allowed a maximum sulfur content of 5% (with the actual average being around 2.67%); their lower sulfur LS fuel counterparts are allowed no more than 1.5% sulfur content . Compare these to the EPA’s imposed limit of 30 ppm for gasoline—or, in the same units, 0.003% sulfur content . The fuel that the ships use therefore contains 500 to 1667 times more sulfur per unit volume than does the gasoline that we are familiar filling our tanks with. By one worst-case estimate, it would only take 16 of the largest type of ships to produce as much sulfur dioxide pollution as all of the cars on the road in the world in the year 2009 . However, the price point of these residual fuels is significantly lower than their more refined counterparts’. With IFO 380 costing only $649 per metric ton (and LS 380 costing $747 per metric ton) it can be difficult for major users to turn away from the cheap stuff .
It is probably folly to imagine that there is a simple way to solve the problem of maritime-generated air pollution. After all, the infrastructure for fuel production and shipment is already very much in place. Purifying the fuel by removing sulfur and other unwanted components would be costly to both the refineries and the customers buying the fuel. Likewise, the monetary loss that would be incurred by replacing engines on these ships would be far from negligible, not to mention the increase in operating costs that would be caused by using pricier fuels. As it stands, there is little incentive for ship owners and shipping companies to change the way that their fleets are powered.
On the bright side, there are currently a number of measures that are available to reduce the amount of emissions produced in the shipment of goods overseas. The most charismatic of these is perhaps the “skysail,” a sort of parachute-shaped sail that can be attached to large ships that takes advantage of prevailing winds to provide additional locomotive power to large ships over long distances . This solution is attractive to shipping companies because it is compatible with whatever other engine system is already installed. The makers of this product estimate that its use could reduce ships’ fuel consumption by 10% – 35% per annum . Even the lower end of this estimate would be considered a significant improvement over the current state of affairs. However, considering how much more sulfur oxides are emitted by ships than by cars per gallon fuel burnt, this figure still seems inadequate in terms of the total reduction of pollution. In order to truly reduce the amount of sulfur compounds released into the atmosphere, it is probable that restrictions will have to be placed on contaminant content within the fuel itself. If this is not done, it seems unlikely that a real decrease in sulfur emissions from ships will be effected.