NGOs Warn Against Discharging Green Ammonia Fuel Wastes at Sea

Every engine room makes wastewater, but carbon-neutral, green ammonia-fueled engines will likely make something new - a concentrated waste solution of ammonia in water, like window cleaner but much stronger. Ammonia effluent will be a new challenge for shipping and its regulators to deal with in the years ahead, and a new source of debate. Industry advocates are interested in a conditional-discharge approach that would allow ships to release the waste at sea, economically, as is done with bilge water. Environmental advocates are pushing for a more protective, more costly no-discharge policy to keep ammonia out of the ocean.

The waste stream comes from the need to deal with a safety issue. Anhydrous ammonia is a useful fuel, but it is hazardous to human health. To mitigate risk, fuel lines must be purged of concentrated ammonia prior to maintenance. The standard way to deal with the purged ammonia from this process is to dissolve it in water, since ammonia gas will readily form a solution and stay put in H2O. That industrial-strength ammonia solution has to be disposed of eventually, and at the IMO's Pollution Prevention and Response (PPR) subcommittee meeting last week, member state representatives took up the question of how it should be handled.

As with other waste streams, there are two available regulatory options: adopt an acceptable standard for discharge at sea; or require the substance to be kept aboard and discharged in port. Industry generally prefers a managed discharge under way, as it is the least costly option, and some member states raised the possibility of a conditional discharge allowance for ammonia effluent during the PPR meeting.

Many of shipping's environmental NGOs are opposed to this idea, even if the ammonia concentrations are diluted below the acutely toxic level at time of discharge. Two risks remain even if concentration is managed, the advocates say: first, chronic toxicity from low-level ammonia exposure in the marine environment; and second, over-fertilization of the ocean surface with excess nitrogen. Too much nitrogen can lead to algal blooms and to deoxygenation of the water, creating harmful conditions for fish and other species.

"The industry has an opportunity to get ammonia fuel right from the start by retaining waste onboard and landing it ashore, rather than defaulting to ocean discharge. This isn’t just about toxicity — it’s about preventing further disruption to a critical planetary system that’s already under stress," said Dr. Lucy Gilliam, Co-executive Director of One Planet Port.

The NGOs call for a prohibition on ammonia discharge at sea, and a requirement to keep the waste stream on board for offloading in port. Ammonia effluent could be used by other industries, they noted, if it could be collected and put to good use on shore.

"If ammonia is used, its waste must stay out of the sea. Ocean health quite simply cannot be collateral damage," said Anaïs Rios, senior shipping policy officer and Clean Shipping Coalition Board Member.