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June 15, 2023

Is SmartCoolant Really Biodegradable? 

Measuring oxygen demand using microorganisms

SmartCoolant Biodegradable Fluids

Here at Submer, we strongly believe that for immersion cooling to be truly sustainable, the dielectric coolant that comes with it must be biodegradable. However, with many dielectric coolants used for immersion cooling such as mineral oils and fluorocarbons, this is not the case. Not only does this make recycling much more expensive, but it also drastically increases the negative impacts which might result from unforeseen spills or releases to the environment. So, how does our SmartCoolant measure up?  

Assessing SmartCoolant  

First things first, let’s get a clear definition of biodegradability: how easily a substance can be broken down by enzymes and microorganisms into simpler molecules such as water and carbon dioxide

Unlike other dielectric coolants, Submer’s specially formulated Smart Coolant is readily biodegradable as certified by independent testing performed as per the Organisation for Economic Cooperation and Development (OECD) Test No. 301F. The OECD 301 biodegradability test is regarded as the leading measure of biodegradability and is a requirement of the EU Ecolabel.  

Submer's SmartCoolant biodegradable fluids

During this test, a sample is placed inside a sealed container with an inoculum rich in naturally occurring bacteria and microorganisms. Over the course of 28 days, the microorganisms will consume the sample and oxygen depending on the biodegradability of the sample. Measuring the ‘oxygen demand’ over time allows us to calculate the biodegradability of the sample. The more biodegradable the sample is, the more oxygen will be consumed

To qualify as readily biodegradable the sample must reach 60% of the theoretical oxygen demand (ThOD) at the end of the 28-day test. As stated in the test description, “the tests are so stringent that it is assumed that such compounds will rapidly and completely biodegrade in aquatic environments under aerobic conditions”.  

Testing biodegradable immersion cooling fluids.
Fig 1. The theoretical oxygen demand (%ThoD) over time for the SmartCoolant (SC1.1 and SC1.2) and a sodium benzoate reference. Test performed by IK4 Tekniker.

Biodegradability vs Stability 

For immersion cooling fluids there is generally a trade-off between biodegradability and long-term stability. For example, vegetable oils are readily biodegradable but quickly oxidise and break down with use. On the other hand, fluorocarbon fluids are very stable but completely non-biodegradable.  

Our carefully designed SmartCoolant strikes a balance between biodegradability and stability, resulting in a readily biodegradable fluid which will remain stable over a long period of time

Biodegradability vs stability of immersion cooling fluids
Fig 2. Biodegradability vs stability for immersion cooling fluids. 


As a result of this exceptional biodegradability, it’s clear that our Smart Coolant stands out among dielectric coolants. This quality is particularly valuable for us as it’s one of our main ways of contributing to a more sustainable and environmentally friendly approach to immersion cooling.   

Got more questions about SmartCoolant? 

The Future of Immersion Fluids

As the only fluid-agnostic player in the immersion cooling space, we’re currently fostering a top-class group of collaborators with an interest in working towards more sustainable services. Through this process, we are building a complete and diverse fluid portfolio and ultimately bringing standardization to the industry to accelerate the widescale adoption of immersion cooling.  

Find out all the details in the video below!