Meet Hullbot: Underwater autonomous robots which clean boat hulls and improve ocean health

Something foul lurks just beneath the surface of countless boats bobbing along in every harbour. Biofouling to be precise: the slime, barnacles, weeds, and algae which grows on hulls, sometimes in just hours, but certainly days, and weeks.

Owners can slow this process by coating the underside with antifouling paints containing biocides which impede the growth of marine life. But these release toxins and microplastics into the ocean, a process which may be further exacerbated by the heavy-duty cleaning necessary to remove biofouling that’s left to accumulate for too long, and they must be re-applied every year.

Now, a Sydney-based startup is using robotics to improve the health of our oceans by reducing biofouling: Hullbot.

“It’s an underwater drone which inspects, maps, and interacts with [and cleans] submerged structures,” Tom Loefler, CEO and Co-Founder of Hullbot, told Cosmos.

“And we’re focused on solving the problem of biofouling whereby, as soon as boats are put in the water, stuff starts to grow on the hull and it occurs in minutes, hours, and days.”

Loefler spoke on the Ocean Impact Innovation Panel at the annual Blue Solutions Summit in Sydney.

“The [vessels] have a slime layer over their surface within several days that can dramatically increase the energy required to push them through the water. And that of course, increases their fuel costs,” he says.

The slime then forms the base for multicellular life to start colonising the hull. This is called macro fouling and Loefler says that it slows boats even more and is also substantially harder to remove.

In 2021, international shipping accounted for about 2% of global energy-related CO₂ emissions (in 2018 it was 2.9% of emissions, 2021 was an anomalous year due to COVID-19). And in Australia biofouling is the greatest source of invasive marine species that destroy biodiversity and alter habitats.

“The robot is able to clean vessels up to 60 metres, which includes yachts, ferries, and other light ships. We intend to put the same core technology into larger robots to address bigger vessels later on,” Loefler says.

By cleaning gently, early, and often with soft brushes, Hullbot can proactively remove early-stage slime before macrofouling begins – without damaging the antifouling paint beneath.

“The more often you clean, the less fuel consumption the vessel will have. So ideally, we clean fortnightly or more frequently than that, to avoid hard growth, and we clean weekly or more often to keep fuel costs as low as possible,” says Loefler.

But why stop there? Loefler believes that cleaning daily with Hullbot could eliminate the need for antifouling paint entirely.

“We would like to offer a solution where hulls are coated with a durable, nontoxic anti foul and cleaned weekly by robots. And in the future, we can see no antifouling coating at all. Just say, a hard gel coat or a hard epoxy coat and cleaning every day with a robot.”

This frequent, light-duty interactions approach is enabled by Hullbot’s advanced robotics, which lowers the cost of each clean so that it can be done more often.

Loefler says that traditionally, underwater robotics has been very limited: GPS, Wi-Fi, 5G and other remote communication doesn’t transmit underwater, neither does LiDAR (which relies on sending and receiving infrared lasers), and advanced acoustics sensors aren’t well suited to doing this particular job.

So, how have they managed it? Hullbot developed a proprietary underwater vision system that uses cameras and code, in combination with a number of other sensors, to enable their robot to know exactly where it is underwater and where it needs to go.

“A number of different cameras interpret the environment around the robot, and planning how it can move through 3D space to inspect or map or interact,” explains Loefler.

“There are many challenges underwater that are unique, such as the distortion of light, the turbidity of the water column… bubbles and other effects. Everything around the robot is moving: the water is moving, the light is moving, the bubbles are moving, and the boat is moving.”

The robot has a tether for power and data and is able to swim freely through the water using its thrusters. It cleans the hull using soft, rotating brushes and both the speed and pressure applied can be controlled – all without a human operator present.

The technology is also being trialled across a number of other applications through partnerships with leading marine industries, marinas, research institutes and environmental organisations.

For example, hullbots are being used to map and analyse natural marine environments like seagrass meadows, kelp forests, and rocky reefs in Sydney Harbour and the surrounds, and can also interact with these environments to collect samples or control pest species.

“We do some projects where we attempt to use the robot to control sea urchin populations where they’re in overabundance and that has the potential to promote the growth of kelp forests,” says Loefler.