CASE STUDY: Improving environmental impact and fish health during sea lice treatment

By: Jan Eric Haagensen, Senior Director, Scandinavia, Moleaer Inc.

A Norwegian fish farm achieved substantially lower CO₂ emissions as well as improved oxygenation levels during their delousing process by adopting nanobubble technology.

Challenges in sea lice management and environmental impact

Managing sea lice in ocean aquaculture systems presents a significant challenge, requiring effective, economical, and environmentally sustainable methods. In Norway, aquaculture companies commonly utilize delousing systems, employing a natural and chemical-free approach. This involves using nets to gather fish near the vessel, subsequently pumping them into a delousing system for the removal and capture of sea lice and their eggs.

Despite the sustainability advantages over chemical treatments, this process has drawbacks. During delousing operations, salmon must be concentrated within pens before suctioning them into delousing lines for treatment. This crowding leads to stress and often results in low oxygen levels. Maintaining optimal oxygen levels during crowding procedures is challenging, given the primary importance of fish welfare to operators.

In attempting to address persistent low oxygen levels and improve fish welfare, a Norwegian aquaculture company initially equipped its vessels with four oxygen cones, powered by two 31 kW pumps, delivering 220 m³ of water at 3 bar each. While the cones succeeded in adequately oxygenating the water, the process proved to be highly energy-intensive and costly. Shifting strategies, the company transitioned to injecting oxygen with diffuser hoses.

While this eliminated the energy consumption of cone pumps, the significantly lower oxygen transfer efficiency required much larger volumes of oxygen, driving up production costs. Additionally, the bubble sizes generated by the diffuser hoses hindered the accuracy of the fish counting system.

Nanobubble technology

In pursuit of a more effective solution, the company opted to try nanobubble technology. In the spring of 2021, the company installed Moleaer’s Trinity L2 nanobubble generator, strategically positioned on a support structure above the connection point of the loading hoses to the delousing system.

The system demonstrated superior oxygen transfer efficacy by injecting only a fraction of the typical amount of oxygen needed to support 200 tons of fish. The successful integration of nanobubble technology marked a significant advancement in not only addressing the company’s oxygenation requirements but also in its initiatives to lower CO₂ emissions.

This system operates in line with water flow, employing high-efficiency gas-to-liquid injection technology. It converts bulk oxygen into nanobubbles, saturating water with elevated levels of dissolved oxygen. The negatively charged nanobubbles, possessing neutral buoyancy, linger in the water for extended periods, serving as an oxygen buffer that stabilizes dissolved oxygen levels.

The generator, designed for permanent operation, has no moving parts, ensuring easy installation and seamless integration with existing pump systems. It can be directly installed in the flow line or in a side stream to enhance oxygen levels in any process. This technology elevates dissolved oxygen levels throughout the water, enhancing growth rates when deployed during feeding, thereby increasing biomass and improving the company’s bottom line.

“Studies indicate that nanobubbles minimize pathogens, foster an environment conducive to reduced disease, enhance gill health, and lower mortality rates. Nanobubbles can also neutralize toxins and waste in water, while concurrently scrubbing surfaces and inhibiting biofilm formation.”

In the operation of oxygenation systems on aquaculture vessels, essential compressors and pumps, powered by diesel, are a major contribution to energy consumption. Direct mitigation of CO₂ emissions is achievable by addressing the energy demand and diesel consumption. Compared with traditional oxygenation systems, such as cones and diffusers, nanobubbles are significantly more efficient. In this case, the Moleaer system demonstrated an impressive 60% reduction in CO₂ emissions compared to cones, factoring in both energy and oxygen consumption during operations.

The Norwegian aquaculture company improved oxygen and energy consumption, reducing CO₂ emissions while providing increased oxygenation to their salmon during delousing crowding: a 63% reduction in energy consumption vs. cone pump + PSA O₂ generator, and a 57.1% reduction in oxygen consumption compared to cones during normal operations. 22.9% reduced oxygen consumption from PSA O₂ generator (while adding a pump) and 73.2% reduced oxygen consumption was achieved compared to diffuser hoses at maximum capacity. The potential payback period for investing in Moleaer’s technology instead of diffuser hoses is calculated at approximately 18 months.

For more information, please contact Jan Eric Haagensen: janeric@moleaer.com