Inch by inch, Jacky Im’s robot climbs a 32-foot (10-meter) steel wall while he watches closely. Each of the 660-pound (300-kilogram) machine’s moves is captured by sensors and compared to a pre-programmed route. Im is so stringent about his robot’s obedience that he wants to catch every wrong turn, even those that can’t be seen with the naked eye. 

He’s not a control freak for fun, though. Im is co-founder of Hong Kong-based Neptune Robotics, a six-year-old startup that deploys waterproof robots to tackle a major challenge facing the maritime industry: decarbonization.

Maritime shipping emits roughly 1 billion tons of carbon dioxide each year, more than Germany, France and Ireland combined. The industry is responsible for about 10% of transportation-related emissions, and as global trade grows, that climate toll is expected to grow with it. The International Maritime Organization, the United Nations body that regulates shipping, predicts emissions from ships will climb 50% above 2018 levels by mid-century. 

To avoid that fate, the IMO is calling on vessel operators to zero out emissions by 2050 and is even considering implementing the first global, mandatory charge on greenhouse gas emissions. Some shipping companies are getting out ahead of any regulatory crackdown by exploring plans to electrify cargo ships, while others aiming to power their fleets with hydrogen, biofuels made from cooking oil and food waste and even the wind. But none of those alternatives can yet compete at scale. 

Neptune is taking a simpler approach. Instead of targeting a ship’s engine, the company’s robots clean up biofouling: the algae, seaweed, barnacles and other organisms that accumulate on hulls, adding drag and reducing fuel efficiency. If half of a ship’s hull is covered by a biofouling layer as thin as a human fingernail, it can increase the ship’s emissions by as much as 30%, according to a 2022 study co-authored by the IMO. 

“It’s like swimming with a thick blanket,” says Elizabeth Chan, a computer programmer who worked in finance and health care technology before co-founding Neptune in 2018 with Im and Kate Ma (a former Deloitte actuary and Chan’s high school classmate). “Our goal is to help shipping companies get rid of that blanket.” 

Neptune’s cleaning service is now available at more than 50 ports in Hong Kong and mainland China, with 27 robots in operation and a new one added every week, on average. Backed by venture investors that include Sequoia Capital, Matrix Partners and SOSV, the company plans to expand to ports in Singapore later this year. 

The company isn’t alone in using robots to combat maritime emissions. Norwegian chemicals giant Jotun A/S has a hull-cleaning robot called HullSkater, which travels with ships and cleans whenever they’re anchored. In Australia, Hullbot developed a robot that performs hull inspection, mapping and biofouling removal.

“Hull condition is among the major parameters for energy-efficient operations of vessels,” says Jason Stefanatos, global decarbonization director of DNV, a Norwegian risk-management firm specializing in the maritime industry. If shipping needs to fast-track decarbonization, “hull-cleaning robots can significantly assist in this effort,” he says. 

When Chan and Im met at a startup incubator in 2018, they knew little about the quest to reduce emissions from shipping. A trained engineer, Im built his first underwater robot for a university contest but struggled to find a real-world use case. 

As Neptune’s prototype was evolving, the co-founders started pitching it as a potential safety inspector for underwater infrastructure. In late 2018, a shipping company agreed to deploy the robot for hull inspection at the port of Hong Kong, where human inspectors are prohibited from entering the water due to heavy maritime traffic. Hull inspection then evolved into requests for hull cleaning, which shipping companies have long employed as a tactic for removing biofouling and mitigating fuel costs. Divers have historically done both jobs, but safety concerns make automated systems more appealing.

Still, handing the work to a robot hasn’t been easy. It took a year to perfect the engineering that allows Neptune’s robots to clean a hull while adhering to the side of it using magnets. And on a trial run in Shanghai, mud from the Yangtze River blinded Neptune’s robot as soon as it descended into the sea, a problem the team hadn’t encountered in the clearer waters off southern China. (The robots now use vacuum-like mechanics to keep mud away from their cameras and image-processing algorithms to help them see.)

Neptune officially launched its commercial hull-cleaning service in 2020 and continues to iterate on its technology at a research and development center in Shenzhen. There, Im and his fellow engineers command camera- and sensor-equipped robots to climb walls in an effort to fine-tune the synergy between software and hardware. Since the robots must be able to withstand tropical climates, icy water and strong winds, the engineers also bake, freeze and shake up robotic components in a series of tests designed to emulate harsh ocean conditions.

The company says its robots can now identify both the type of biofouling on a ship’s hull and its thickness. An operating system backstopped by artificial intelligence maps out a plan for each ship, and the robot engages in “cavitation cleaning” — vibrating biofouling off the hull with high-velocity microdrops of water, not unlike how a jeweler removes dirt and grease from a tarnished necklace. The biofouling is collected and taken back to shore for disposal. 

Neptune says its robots have cleaned more than 700 vessels since 2020, helping the industry avoid roughly 1 million tons of CO2 emissions. Shipping companies can subscribe to a customized annual package or book the service as needed. While pricing varies based on the size and scope of the job, Chan says each operation costs between $12,000 and $40,000. Neptune calculates that its cleanings reduce fuel consumption per trip by at least 18%. 

If a vessel has biofouling, “the subsequent fuel savings from cleaning can equal or even exceed the cost of cleaning,” says a spokeswoman for commodities giant Cargill Inc., which has deployed Neptune’s service for its bulk carriers since 2022. As the shipping industry starts to transition to alternative fuels with a lower carbon footprint but a higher price tag, “any fuel saved will be more valuable, so the imperative to keep ship hulls clean remains in the future,” she says.  

Stopping biofouling buildup isn’t just good for the climate: Many scientists have sounded the alarm on ecological threats posed by invasive species that hitchhike on ships. In recent years, Australia and New Zealand tightened scrutiny of ships arriving in their waters, including requiring regular removal of biofouling. California, home to some of America’s biggest ports by cargo tonnage, also requires biofouling management.    

That looming regulatory risk, combined with fuel-saving benefits, has translated into rising demand for commercial hull cleaning. Last year, Neptune conducted 533 cleaning operations, compared with just 16 in 2020. 

But scaling up its technology will bring new hurdles. The AI-backed robots largely operate on their own, but humans are still needed to launch them from an operation boat nearby and to review the cleaning job when they’re done. And while Neptune’s robots can remove biofouling attached to most of a hull’s surface, they still fail to tackle niche spots such as propellers.

On their own, Neptune’s robots are also incapable of yielding the kinds of dramatic emissions reductions that will be necessary to meet the IMO’s 2050 goal. For that, other climate-friendly alternatives will have to scale up, and shipping operators will ultimately have to switch away from fossil fuels.

Until then, it’s underwater robots to rescue. Says the Cargill representative: “It is something we can deploy at scale, today.”

To contact the author of this story:

Coco Liu in New York at [email protected]