Technology group Wärtsilä has been contracted to supply its Wärtsilä 25 Ammonia auxiliary engine, along with a selective catalytic reduction (SCR) system and gas valve unit (GVU), for two newbuild 51,350 cbm mid-size LPG/liquid ammonia carrier vessels.

The ships are being constructed at the Nantong CIMC Sinopacific Offshore & Engineering (SOE) shipyard in Nantong, China, and will be owned by Navigator Amon Shipping AS, a joint venture between Navigator Gas and Norway-based Amon Maritime. Wärtsilä will also supply the propulsion system for both vessels, including a controllable pitch propulsion solution. The order for the engines, SCR and GVU was booked by Wärtsilä in Q2 2026, while the order for the controllable pitch propeller system was booked in Q3 2026. Equipment delivery to the yard is scheduled to begin in June 2027.

According to Wärtsilä, when running on sustainable ammonia, total greenhouse gas emissions can be reduced by at least 90% compared to equivalent diesel engines. The company introduced what it describes as the marine sector’s first commercially available four-stroke engine-based solution for ammonia fuel in 2023.

Kaj S. Pilemand, Director of Vessel Operations at Navigator Gas, remarked: “Wärtsilä has demonstrated industry-leading capabilities in enabling future low and zero-carbon fuels to become viable. By selecting the Wärtsilä 25 Ammonia engine, we expect to dramatically reduce the ships’ environmental impact, while supporting compliance with evolving regulatory requirements.”

The engines are intended to help the vessels meet current and forthcoming environmental regulations, including the International Maritime Organization’s (IMO) net-zero emissions target for 2050. Ammonia is a carbon-free fuel and is being explored across the shipping sector as a means of meeting long-term decarbonisation goals.

Stefan Nysjö, Vice President of Power Supply at Wärtsilä Marine, commented: “This project reflects the continued momentum behind carbon-neutral and zero-carbon fuels, with ammonia emerging as one key pathway. It also highlights the growing demand for flexible propulsion solutions that support new, more sustainable operating models. In short, these vessels have been designed for lower-emission operations, and Wärtsilä’s solutions will support those ambitions.”