Ammonia wastewater discharge at sea is emerging as another issue as global rules for the fuel take shape. File Image / Pixabay

Shipping's adoption of ammonia as a marine fuel is facing fresh scrutiny over how to handle ammonia-contaminated wastewater generated onboard, with environmental groups and several countries divided on whether any discharge at sea should be allowed.

The issue is being discussed this week at the IMO's Pollution Prevention and Response (PPR) subcommittee meeting as the UN-body works toward global guidelines for managing ammonia effluent from ships.

A group of environmental NGOs has urged the IMO to reject proposals that could allow ammonia-fuelled vessels to discharge ammonia effluent at sea, arguing this would normalise the ocean disposal of toxic waste, they said in an emailed statement on Friday. 

Ammonia effluent refers to wastewater containing small amounts of ammonia formed when unburned ammonia mixes with water during bunkering, engine operation or exhaust cleaning.

The NGOs have called for all ammonia effluent to be retained onboard for discharge ashore. They claim some member states at this week's PPR session discussed a framework that could permit the conditional discharge of ammonia effluent into the ocean.

Member States Seek Practical Guidelines

However, some countries and industry stakeholders say operational realities also need to be considered as the IMO develops guidelines.

In a submission to the IMO, Japan said future rules should include provisions covering application, exceptions, control of discharges, and discharge procedures and standards, while taking account of different operating scenarios.

Referencing the IMO's interim safety guidelines for ammonia-fuelled ships, Japan noted that operations can fall into three categories: normal operation, foreseeable and controllable abnormal scenarios, and emergency situations.

South Korea and classification society RINA said in a separate proposal that a strict prohibition on any discharge would mean effluent must either be stored onboard for later discharge ashore or treated onboard.

They argued this could raise safety and operational concerns, as storing large volumes of ammonia-contaminated wastewater would require additional tank capacity, increase crew-handling risks and place pressure on ship operations, particularly where adequate shore reception facilities are not available.

The outcome of the PPR discussions is expected to shape how ammonia effluent from ships is managed globally, with stakeholders warning that the approach taken could influence the pace of ammonia adoption as a marine fuel.