In an effort to curb their air pollution, cargo and cruise ships have been forced to reduce the sulfur in their emissions since January 2020.
Rather than switching to cleaner-burning fuel, many ships turned to a piece of technology that scrubs some of the pollution out of the exhaust from the fuel — and splashes it back into the ocean.
A new study reveals that ships pour 10 gigatons, or 10 billion metric tons, of that polluted water into the ocean in a year. And Port Everglades, PortMiami and ports in the Caribbean are some of the top dumping grounds.
"This isn't being distributed in the global ocean, it's being concentrated in the areas where we're already concerned about marine life," said Dan Hubbell, shipping emissions campaign manager for the Ocean Conservancy.
Environmental advocates have long raised the alarm on scrubbers, the machines ships use to suck the sulfur out of their emissions and dump a liquid version of it into the ocean. Since the International Maritime Organization's new law requiring ships to cut out the sulfur they spew took effect in 2020, instead of switching to low-sulfur fuels, the largest cruise companies have overwhelmingly outfitted their ships with scrubbers as a cheaper solution.
The new study from the non-profit research organization International Council on Clean Transportation attempts to quantify for the first time just how much scrubber wash water is being dumped into the ocean using global shipping traffic data from 2019, ships' scrubber wash water flow rates and energy demands.
Researchers found cruise ships were the main culprits for discharges in port waters. Georgetown in the Cayman Islands experienced the most scrubber discharges, all by cruise ships, accounting for 14.1% of the total amount discharged in ports. Freeport and Nassau in The Bahamas ranked third and fifth for most scrubber wash water discharges, followed by St. George's, Grenada, in sixth place. Port Everglades and PortMiami ranked 10th and 11th for most discharges — the most of any ports in U.S. waters.
"This study shows the consequences of regulating pollutants rather than pollution," said Bryan Comer the head of the ICCT's marine program. "In its effort to reduce sulfur dioxide emissions, the International Maritime Organization has created a global water pollution problem. Individual countries and ports now must decide whether to allow ships to continue to dump pollution in their waters, without compensation, or to ban the use of scrubbers in their waters."
'Minimal impact' or 'witch's cauldron'
Because scrubber technology is relatively new, there's not a huge body of research showing the potential impact of wash water discharge, but initial studies suggest it could post a significant problem. The IMO is still reviewing scrubber wash water's effects on the ocean.