Fighting shipping pollution may be bad for the planet
The shipping industry is getting serious about cutting sulfur dioxide emissions. People who live along busy shipping lanes will see health benefits from reduced particulate emissions and a reduction in acid rain when new regulations come into force on Jan. 1. But the sulfur particles help offset some of the warming caused by powering the ships, so the rules may also increase the likelihood that rising sea levels caused by global warming leave those same populations without a home.
The new regulations from the International Maritime Organization, a United Nations agency responsible for ensuring safe and efficient shipping on clean oceans, allow for two ways of tackling the problem. Either ships must burn fuel with a sulfur content of no more than 0.5 percent down from the 3.5 percent that is currently permitted outside of designated special emission-control areas. Or they must install scrubbers to remove sulfur from their exhaust.
The change targets the public-health impact of shipping, which is estimated to contribute 13 percent of total sulfur oxide emissions annually. It will slash the amount of sulfur dioxide from ships by 75 perecent. Doing so will dramatically reduce premature deaths resulting from sulfate emissions from ships, according to a paper published in Nature Communications in 2018 by a team of researchers from U.S. institutions and the Finnish Meteorological Institute.
Health benefits
Most of the health benefits will be felt by communities in coastal regions of densely populated countries with busy ports or those on major sea-trade routes, especially in India and China. People living near coastlines in the United States or Europe won’t see a difference since ships operating in those areas already face far stricter limits that restrict them to burning fuel with a maximum sulfur level of 0.1 percent.
But these health benefits may come at a cost of actually worsening shipping’s climate impact. That’s because the sulfates from ships’ exhaust emissions contribute a cooling effect that will be lost with their removal.
Sulfur aerosols from ship exhaust reflect energy back into space. But they also help make clouds brighter, so they reflect more sunlight away from the Earth as well.
The sulfur puzzle is just one piece of IMO’s efforts to clean up an industry that’s crucial to keeping global trade flowing, with more than 80 percent of global trade carried by sea. A study, published in 2014, estimated that in 2012 international shipping accounted for about 2.2 percent of all manmade carbon dioxide emissions, and that such emissions could grow by between 50 percent and 250 percent by 2050.
In 2018, the Londonbased group adopted a strategy to reduce greenhouse gas pollution. The goal is to cut the carbon intensity of international shipping “by at least 40 percent by 2030, pursuing efforts towards 70 percent by 2050, compared to 2008,” according to the document. It also aims to bring about a peak in total greenhouse gas emissions as soon as possible and reduce them by at least 50 percent by 2050 compared with 2008 levels. The overall emissions target is lower than the carbon intensity goal because the volume of shipping is forecast to increase over the next 30 years.
One proposal to help achieve all of this is to lower fuel consumption by introducing speed limits. Others include technical approaches such as mandatory power limits.
Where sulfur dioxide emissions are concerned, some of the negative climate impact may be offset by a parallel reduction in organic carbon and black carbon particles from ship exhaust, which have strongly warming properties. Low-sulfur fuels contain fewer black carbon particles and scrubbers remove them alongside the sulfur. They also have another important component: They are extremely expensive.
Compliance premium
The higher cost of IMO 2020-compliant ship fuel and the fact there is no single worldwide specification for compliant fuel may in and of itself increase the incentive for ship operators and charterers to cut consumption, Corbett argues, thereby reducing CO2 emissions.
Until an industry-wide greenhouse gas strategy is adopted and implemented that may be the best hope we have.