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Regulations Usher In Era of Cleaner Emissions at Sea

Michael Atkins


  • Discusses how the latest cap on sulfur oxide emissions would reduce emissions by more than 8 million metric tons annually and prevent some 570,000 premature deaths over five years.
  • Addresses existing international maritime law that mandates ships’ voyage plans account for environmental protection measures.
  • Comments on how Annex VI amendments will require ships to calculate and monitor the energy efficiency and carbon intensity of operations.
Regulations Usher In Era of Cleaner Emissions at Sea
Felix Cesare via Getty Images

Newly released data suggest that a recent marine environmental mandate aimed at abating air pollution along coastal zones and around major ports has achieved high rates of compliance, allaying widespread concerns regarding its implementation. 

The rule, Regulation 14 in Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL), took effect globally in January 2020, targeting harmful emissions at shipboard sources by setting the maximum allowable sulfur content of fuel oil burned by seagoing vessels at 0.5 percent. That’s down from a 3.5 percent cap in place since 2012. An amendment to Regulation 14, in effect since March 2020, prescribes the same level to all fuel carried on board those vessels. The usage limit is even stricter, at 0.1 percent, within designated emission control areas (ECAs), which encompass most territorial waters and economic exclusionary zones of the United States. These standards are part of a broader scheme promulgated by the International Maritime Organization (IMO), a specialized agency of the United Nations (UN), through MARPOL, the principal environmental regulatory code applicable to the global shipping industry.

Historically, most ships sailing the world’s oceans––from supertankers to container ships to roll on/roll off carriers and others––had been powered by lower-grade residuals. Last year the IMO estimated a 70 percent cut in sulfur oxide emissions from ships because of the new 0.5 percent mandate. Exposure to sulfur oxide emissions has been linked to respiratory, cardiovascular, and lung disease, and emissions can lead to a litany of environmental impacts, both on land and at sea. A study in 2016 by the Finnish Meteorological Institute projected the latest cap would reduce emissions by more than 8 million metric tons annually and prevent some 570,000 premature deaths over five years, yielding outsized benefits in coastal communities and areas proximate to major shipping lanes. 

In the lead-up to 2020, though, speculation swirled among public and private stakeholders, wary of low supplies and the high costs of compliant bunkers, which include very low sulfur fuel oil (VLSFO) blends, and marine gas oil (MGO) and marine diesel oil (MDO) distillates. As the compliance deadline loomed, the IMO sought to assuage concerns, issuing safety guidance and monitoring reports of compliant fuel non-availability, submitted under Regulation 18 of Annex VI. New reports suggest a smooth transition. As of February, the IMO had fielded just 61 fuel oil non-availability reports (FONARs), indicating supplies have been strong. IMO sampling data was likewise encouraging. Of 136,938 samples taken from 116 million tons of residual fuel supplied for use onboard ships in 2021, nearly 75 percent did not exceed 0.5 percent sulfur content. Of 85,097 samples from 15 million tons of distillate fuel, more than 99 percent did not exceed 0.5 percent. And research prepared in the fall by Oak Ridge National Laboratory–– which characterized compliance as “near universal”––showed VLSFO had been the most-sold petroleum-based bunker fuel at ports in Singapore and Rotterdam after the rule took effect, attributable in part to a narrower-than-expected price spread between VLSFO and the 3.5 percent high sulfur fuel oil (HSFO).

Importantly, alternative means of compliance, such as installing exhaust gas scrubbers or using biofuels, are permissible under MARPOL, enabling ships equipped with such systems to burn fuels of a higher sulfur content. As of February, the IMO had received 3,765 reports of ships equipped with exhaust gas cleaning systems, a 19 percent increase since March 2021, along with 13 reports of biofuel-powered vessels. The use of alternative fuel sources––liquefied natural gas (LNG), methanol, hydrogen, ammonia, etc.––is expected to increase over the long-term, as outlined recently by researchers from the University of Saskatchewan.

MARPOL, adopted in 1973 and amended in 1978, contains rules designed to prevent and mitigate pollution by ships from operational or accidental causes. Its genesis can be traced to a spate of high-profile oil spills, among them the Torrey Canyon tanker grounding that soiled British and French beaches in 1967 and, two years later, an oil platform blowout off the coast of Santa Barbara, California. The convention has since broadened beyond oil discharges to cover other pollutants; today its annexes extend to noxious liquid substances, packaged cargo, sewage, and garbage. Annex VI of MARPOL, adopted by protocol in 1997, targets air pollution–– including emissions of sulfur oxides, oxides of nitrogen, and particulate matter––from ships. The fuel carriage and usage rules, drafted by the IMO’s Marine Environment Protection Committee (MEPC), appear primarily in Regulations 14 and 18 of the air annex. The United States is party to Annex VI, having submitted its instrument of ratification in 2008. At present, according to the IMO, there are more than 100 contracting states to the 1997 protocol, representing 96.75 percent of the world’s shipping tonnage.

The fuel rules, like other MARPOL provisions, are incorporated domestically through a statute enacted in 1980 called the Act to Prevent Pollution from Ships (APPS), 94 Stat. 2297, 33 U.S.C. §1901 et seq. Lead agencies, as delegated by the APPS, are the Coast Guard and the Environmental Protection Agency (EPA), which undertake regulatory functions––rulemaking, inspection, certification, enforcement, etc.––in accordance with an MOU signed in 2011. Duties are divided according to agency expertise. For example, the Coast Guard conducts onboard materiel surveys and issues the International Air Pollution Prevention Certificate (IAPP), signifying compliance. Within the EPA’s province is the certification of main and auxiliary engines with an output greater than 130 kilowatts (kW) and the issuance of corresponding Engine International Air Pollution Prevention (EIAPP) certificates, which attest to adherence to nitrogen oxide emissions requirements in a laboratory setting. The EPA also verifies compliance with fuel oil availability and quality and maintains a register of local suppliers of fuel oil. The Coast Guard, meanwhile, examines bunker delivery notes and fuel samples during its onboard inspections. Representatives of the EPA may attend Coast Guard inspections or investigations related to fuel oil availability and quality.

When an onboard inspection by the Coast Guard indicates non-compliance with rules related to fuel quality, enforcement action is pursued under authorities granted by the APPS. At the outset, the Coast Guard might issue a detention order, preventing the vessel from returning to sea unless it can do so without presenting an unreasonable threat of harm to the marine environment or the public health and welfare. A continuum of further enforcement options exists, ranging from minor administrative measures for small offenses, such as a Letter of Warning (LOW), to civil fines and criminal prosecution in more egregious cases, typically handled in tandem with the Department of Justice. Most violations land somewhere along this spectrum, and in such cases the Coast Guard would, by policy, refer the matter to the EPA for enforcement action. A sample of civil enforcement cases brought against shipowners by the EPA under APPS is available online.

Port state control officers from the Coast Guard conducted 7,383 exams of foreign-flagged vessels making port calls to the United States in 2020, and of the 2,877 deficiencies issued, only 27––or, 0.93 percent––were related to MARPOL air regulations infractions, according to the most recent annual data released by the service. As noted, two ECAs cover waters off both Pacific and Atlantic coasts and in the Gulf of Mexico, and engine room crews often must conduct fuel changeover procedures prior to entering an ECA. Existing international maritime law mandates that ships’ voyage plans account for environmental protection measures that apply along intended routes, avoiding actions that could cause damage to the environment. 

With the sulfur content rules fully implemented, the MEPC has shifted its attention to greenhouse gas (GHG) emissions. Annex VI amendments will require ships to calculate and monitor the energy efficiency and carbon intensity of operations. Ship-specific ratings based on those calculations are expected to begin in 2024. In December, the IMO doubled down on climate change initiatives, initiating revisions to a GHG strategic plan and resolving to cut black carbon emissions in the Arctic. At present, the GHG strategy aims to cut carbon emissions by at least 40 percent by 2030 and 70 percent by 2050, compared to 2008 levels.