PLEN raises the freezer temperature

Particularly sensitive biochemical samples are stored in ultra-low temperature freezers (ULT freezers) at minus 80 degrees Celsius, and that’s just how it is! Or so it was at the Department of Plant and Environmental Sciences until they took the decision of adjusting the freezer temperature to save energy and extend the lifespans of the freezers. The department is now setting the freezer temperature at minus 70 degrees instead of minus 80 degrees – for the benefit of the environment as well as the bottom line. 

“It all started when we read an article in a laboratory magazine that many laboratories are raising the freezer temperature,” says Niels Agerbirk, plant biochemist. The game changer was an online sheet where research groups from around the world were sharing information about which samples they were keeping at minus 70 degrees. “We opened the sheet and looked for research groups that we knew and who we felt like we could trust. And we found some. If they are adjusting their freezers to minus 70 degrees and can vouch for it, we can do it too,” the plant researchers decided.

But there was some way to go from taking the decision of adjusting the freezer to putting that decision into practice. Laboratory coordinator Tilla Engelsted and precision mechanic Flemming Frederiksen played key roles in this process.

 “We could find no evidence for neither minus 70 nor minus 80,” says Tilla Engelsted. 

Minus 80 degrees is an informal standard for storing biochemical samples. The standard has changed over the years as freezer technology has advanced to keep lower temperatures. This is how the temperature landed at minus 80 degrees – or in some cases even minus 86 degrees. 

“Since there is no evidence for neither minus 70 nor minus 80 degrees, we might as well choose the energy- and climate-friendly option,” says Tilla Engelsted. 

Green Campus has conducted tests and thereby documented energy savings of 20-22% by adjusting the freezer temperature from minus 80 to minus 70 degrees. But that’s not the only benefit. At minus 70 degrees, the freezer compressors don’t have to work as hard, and as a result, the expensive freezers last longer. 

 “The motivation for the change was driven by climate considerations – and long-term financial considerations, because the freezers last longer,” says Tilla Engelsted. 

The faculty, which pays the energy bill, is also benefiting from this by reducing energy costs as well as carbon emissions.

The users couldn’t say why the freezers had to be at minus 80 degrees

Precision mechanic Flemming Frederiksen had also noticed that the very low temperature was taking a toll on the freezers, and he, too, was starting to push for change. “When we asked the users of the freezers, they didn’t know why it was important to keep the freezers at minus 80 degrees,” he says. He realized that some of the freezers were working very hard to keep the temperature at minus 80 degrees and thought that a temperature increase of 5 degrees might expand the freezer lifetime with extra two years. “Even a 5 degree increase from minus 80 to minus 75 degrees makes a huge difference in terms of energy consumption. Especially for old freezers.” The temperature can, however, not be adjusted for all freezers: some of the oldest freezers are built for minus 80 degrees, and the freezers cannot be adjusted to minus 70 degrees, according to the manufacturers. This is the case for some of the freezers at PLEN, too, so these are kept at minus 80 degrees. Across the department, 15-20 of their ULT freezers are now adjusted to minus 70 degrees.

No resistance from the users when adjusting the freezer temperature

The change from minus 80 to minus 70 degree did not cause resistance in the section. “We did not force anyone. We left the old freezers, which could not have their temperatures changed, at minus 80 degrees. We offered that people could use those freezers if they did not feel comfortable keeping their samples at minus 70 degrees,” says Niels Agerbirk. Most people are, however, preferring the new freezers at minus 70 degrees. “As a researcher, the greatest fear is that the freezer will break down. Therefore, many people are preferring the new freezers – even though they are 10 degrees warmer,” says Tilla Engelsted. And researchers as well as students like that they have reduced their climate footprint.

When purchasing new ULT freezers, it is now taken into account whether the freezers perform well at minus 70 degrees. The common procurement agreement for ULT freezers at UCPH allows for this consideration – and the freezers are more energy-efficient than others on the market, too.

In the Plan Biochemistry section there’s a long way from changing the temperature to changing the language. “Many people are still calling them ‘minus 80 freezers’ because that’s what we always called them,” says Tilla Engelsted. Niels Agerbirk and Tilla Engelsted agree that the appropriate name is ULT freezers, and they suggest to mention the ULT freezer temperature in publications to spread the word of minus 70 degrees being sufficient.