New catalyst cuts 99% of emissions from ammonia-fueled ships

South Korean researchers have developed a technology that could resolve a key environmental dilemma facing ammonia-fueled ships — vessels that emit a greenhouse gas with a global warming potential 300 times that of carbon dioxide. The new system uses a single catalyst to remove 99 percent of both nitrogen oxides and unburned ammonia produced during combustion, while also effectively treating nitrous oxide, whose warming impact far exceeds that of CO₂.

The Korea Institute of Energy Research announced Thursday that a research team led by Dr. Hwang Seon-mi of the institute's Clean Air Research Laboratory, under its Climate Change Research Division, had developed an integrated catalyst technology capable of treating multiple exhaust emissions from ammonia-powered ships.

Ammonia is widely regarded as a next-generation clean fuel for the shipping industry because it produces no direct carbon dioxide emissions when burned, and is relatively easy to transport and store. In practice, however, combustion in marine engines generates nitrogen oxides (NOx), nitrous oxide (N₂O) and unburned ammonia (NH₃). Nitrous oxide in particular is classified as a potent greenhouse gas, and failure to treat it adequately could undermine the carbon-reduction benefits of ammonia as a fuel.

Existing exhaust treatment systems for ships compound the problem. Diesel vessels are designed primarily to remove nitrogen oxides, but ammonia ships must also handle nitrous oxide and unburned ammonia. Installing separate catalysts and equipment for each pollutant would significantly increase space requirements, weight and cost.

The research team addressed the problem by developing a "hybrid catalyst" that simultaneously breaks down nitrogen oxides and unburned ammonia. A single catalyst layer removes both substances at roughly 99 percent efficiency, and the amount of catalyst required can be cut by up to half compared with conventional approaches.

Existing precious-metal-based catalysts for ammonia decomposition are expensive and can generate additional nitrogen oxides during the treatment process. The team's catalyst cuts costs by at least 80 percent compared with precious-metal alternatives.

The team also developed a separate technology for treating nitrous oxide. Their nitrous oxide decomposition catalyst operates at a temperature about 100 degrees Celsius lower than existing commercial catalysts, and can decompose more than 99 percent of nitrous oxide at 350 degrees Celsius — conditions similar to actual ship exhaust environments — without requiring a separate reducing agent.

The research team noted that both catalysts are compatible with exhaust treatment equipment already used on diesel ships, reducing the need for large-scale retrofits. Given the limited space aboard vessels, the technologies also offer advantages in terms of equipment miniaturization and weight reduction.

"This technology can simultaneously reduce multiple pollutants, which has been the biggest challenge for ammonia-fueled ships," Hwang said. "It reflects real-world demands for reduced installation space, lighter systems and improved maintenance efficiency."

She added that the institute plans to refine the technology through pilot demonstrations and support its commercialization to help South Korea's shipbuilding and shipping industries gain a competitive edge in the clean-vessel market.

The research was conducted as part of the Korea Institute of Energy Research's core program, and the findings were published in Applied Catalysis B: Environment and Energy, an international journal covering energy and environmental science.