Fridges and Freezers can consume a surprising amount of energy. They can account for 5%+ of a laboratory’s electricity use. A -80°C (Ultra-Low Temperature - ULT) Freezer uses as much energy as a home, and that doesn’t include the significant cooling required to balance the heat output from the freezer coils.
Preventative Maintenance
Fridges and freezers should undergo annual inspections and preventative maintenance. It is important for increasing the longevity of the fridge/freezer, bringing energy savings, improving sample security, and reducing the risk of failure. The savings generated from proper maintenance can easily cover the costs of this work.
Maintenance also includes regularly vacuuming the dust from intake and coils. Ensure filters are not blocked. Scrape down the seals to prevent ice buildup. Check that airvalve has not frosted over.
Make a sign-off record of routine maintenance actions.
Harvard University provides free preventative maintenance to all lab freezers (e.g. filter changes, inspections). They found that their total savings was larger than the cost.
Fridge/Freezer Inventories
A fridge/freezer inventory reduces the likelihood of misplaced samples and improves sample access speed. Most energy is wasted during door openings. Knowing where your sample is in your fridge/freezer can keep the door opening time to a minimum. Consider an electronic searchable inventory.
Examples: LabGuru, Freezer Works, Labkey, eLabInventory, Quartzy, Genemod, Labarchives, ProCuro, RedCap
ProCuro - Used at University of Bristol - Customisable and easy to navigate, have multiple user ID logins, surprisingly smooth output to Excel, compatible with bar code readers. It can be somewhat time consuming to log samples, but probably not different than any other inventory software.
Regularly Defrost
Defrosting freezers should be part of your regular maintenance schedule. It helps ensure there is no build-up of ice on the seals. Ice also takes up storage room and can give you the illusion that your freezer is full, making you think you need a new one. Plus, if the temperature probe is covered in ice, the actual temperature can be off by 5°C.
To defrost a freezer
A. Move out your samples on a Friday evening
B. Unplug and prop the door open (Check manual for proper turn-off sequence)
C. Place towels or cardboard underneath the door to catch the water
D. Let the freezer sit for the weekend to dry out
E. On Monday, remove the towels/cardboard (Once cardboard is dried, it can be recycled)
F. Sanitize
G. Turn on again
H. When freezer has reached operating temperatures, move your samples back
Do an Annual Clean Out
Most labs, especially those who do not have, or have out-of-date inventories, do not know what is in their fridge/freezer. Freezer clean-outs conducted in labs at UC Davis and the CDC found that 10-30% of items stored in refrigeration units were no longer needed or no longer viable. Doing a freezer clean out makes sample finding faster. It also frees up room in existing freezers, enabling consolidation, and reduces the need to buy new freezers.
Label your samples well. When people don’t know what the samples are, they tend to put them back in freezer just-in-case.
Also have a protocol in place for people leaving the lab. They should go through and dispose of all their samples with the exception of a few that can be gifted or need to remain in archives. However, ensure that these samples now have a new owner specified. These samples now belong to that person and they are responsible for it.
Check your Operating Temperature
An ultra-low temperature freezer set to -70°C instead of -80°C uses up to 40% less energy. In addition, it causes less stress on the compressor, which will increase the life of your freezer and decrease the risk of unexpected failure. Also, the freezer releases less heat, meaning that it will cost you less to cool down the room.
There have been some publications proving that DNA, RNA, antigens, viruses and competent cells are stable at -70°C for more than 20 years. A list of samples which researchers are storing at -70°C can be found here. Please add your samples!
There are a number of publications on this topic:
PON1 LT stability -20, -70,.pdf (170.9 KB)
RNA stability 4, -20, 10 FzTh ISBER Poster 2011.pdf (68.5 KB)
Serum AntiOX LT store -20, -70 Jansen.pdf (136.7 KB)
Upright ULF T variability BBI Poster.pdf (40.4 KB)
Viral Stability -20 CVS2008.pdf (281.7 KB)
-70 for microorganisms.pdf (43.9 KB)
-70 for storing protein.pdf (264.9 KB)
Room Temperature Sample Storage.pdf (533.9 KB)
-20 for storing DNA.pdf (229.0 KB)
DNAstorageandquality-1.pdf (421.1 KB)
DOI: 10.1128/JCM.42.3.1257-1259.2004
DOI: 10.1007/s42398-023-00297-2
DOI: 10.1186/1476-511X-11-53
This reasoning extends to normal freezers. For example, we’ve noticed that Australian labs set their freezers to -30°C whereas in North America and UK, they are only set to -20°C.
Ensure the thermometer is not covered in ice and functions properly. Use a second temperature probe if necessary.
Convincing your collegues to go from -80°C to -70°C
- Show them the published papers about biomolecule/cell storage (see above for links)
- Share with them the sucesses at other Unis and the lists of things they store at -70°C (see above for link)
- Tell them about the history of freezers - back in the day when -80s used to be -60s
- It appears that -80s became popular mainly due to successful marketing.
oc8b00705-compressed.pdf (787.7 KB)
- Rationalize with them using the recystalization points of water
- Discuss with them the “this is the way we’ve always done it” mentality - For example, there are some labs who set their ULTs to -86°C and some labs set their -20°C to -30°C. But the research they do is the same as ours… does the extra 6°C (and 10°C) means ours are not stored properly?
- Dispel the myths. No, -80 is a default set point NOT because it is close to the temperature of dry ice.
- Keep a back up or have a control. Keep one copy of that all important DNA in a -80°C freezer that you share with many other labs. Then keep the rest of your samples in the -70°C. If the worst happens, you can always reproduce from that one copy. Also, store your quality control samples with your unknowns, so you can compare to be sure.
Downgrade your Cold Storage
A -20°C freezer consumes 80% less energy than a ULT freezer and room temperature storage costs almost nothing. By storing your samples and reagents at warmer temperatures, massive energy savings can be accrued.
Many reagents and samples do not require storage at ULT temperatures. For example, there is evidence that DNA can be stored in a standard -20°C freezer. -20 for storing DNA.pdf (229.0 KB)
here
Look to buy DNA, plasmids, regents, and testing kits that can be stored at room temperature. In addition to saving energy, these products don’t require refrigeration in the supply chain. They don’t need to be stored cold at the supplier and don’t require dry ice, ice packs and Styrofoam boxes when shipped to you.
ThermoFisher estimated that their Custom Primers and TaqMan® Probes divert 5,062 cubic feet of expanded polystyrene (also incorrectly known as Styrofoam) and reduced their carbon footprint by 38 tons CO2e per year.
SampleMatrix® by Biomatrica® (Millipore Sigma) allows storage and shipping of biological materials at room temperature without degradation. DNA or RNA is added to the matrix at the bottom of the tube, dried down and when needed, eluted out. This is great for long term storage or backup DNA/RNA copies. - Product may be discontinued
For shipping and storing plasmids, spot on blotting paper. When you need it stuff it into an Eppendorf tube, and let it soak in some water.
Antibodies can last decades in the fridge. I know a lab that has antibodies fractionated in ethanol from like the 80s, and they can still use it. It’s the conjugation and/ or the conjugated moiety that is unstable, if the antibody is conjugated.
Increase Storage Density
Most labs use fridge/freezer boxes that store only 81 samples (9x9 dividers) or 100 samples (10x10 dividers). In order to maximize existing space, consider switching to high-density storage (13x13 dividers) or smaller tubes. This will allow you to fit more samples in a single fridge/freezer.
Combine Storage with Other Labs
If your lab does not need a whole fridge/freezer, you can share with an adjacent lab. This keeps your fridge/freezer full, which increases efficiency, and reduced your need to buy and run extra fridge/freezers.
Consolidating freezers into one room (i.e. having a freezer farm) is more efficient because it allows you to install a dedicated air handler to capture rejected heat and exhausted out of the building.
Purchasing
A fridge/freezer is a piece of equipment you are purchasing that, from the day it is delivered, will be on 24/7/365 until it fails.
There are many other considerations, such as insulation, inner-door insulation and gaskets, sealing gaskets, refrigerant type, configuration/layout, compressor run time percentage, heat exchanger type, noise output, and heat output, when deciding on the most sustainable freezer for your lab needs.
As a shortcut, look for Energy Star® rated freezers. These freezers use 60% less energy than standard-efficiency models.
Minimum Standards
Look for fridges and freezer perform better than the standards below:
ULT freezers:
13.5 watts/litre/day or less
If larger than 500 L, 10 kWh/day or less
-20C Freezer
2.5 watts/litre/day
1.5 kWh/day
4C Refrigerator
2.5 watts/litre/day
1.5 kWh/day
The actual energy consumption depends on many factors. Read the paper by Gumapas and Simons (2013).
Considerations
Larger units use energy more efficiently, but don’t buy a freezer larger than your requirements. If possible, partner with another lab to share a freezer.
Chest freezers keep cold temperatures significantly better than upright units, but require more floor space and may be more difficult to find samples.
Spark-free freezers are only necessary if used in labs containing combustibles.
Take the manufacturer’s data with a grain of salt. Their energy figures often do not represent actual use. In addition, test conditions vary between manufactures. Request information about their testing conditions when evaluating a freezer’s energy numbers. Energy Star® has a standard test protocol for companies to use. Although we find that they still do not represent actual use, the test conditions are standardized across the board and helps when comparing between manufacturers.
When comparing energy usage data, convert all to kWh/litre. Much of the data is provided without accounting for the freezer/fridge size.
Choose units where there is
- A set temperature display vs just a dial
- A display with the actual temperature
Do not choose units with auto-defrost cycles
Opt for drawers - Green Light Labs measured that if you removed the drawers from a -20C freezer the temperature rise following door opening is 3x higher
Disposal
Appropriate disposal is extremely important because many contain chlorofluorocarbon (CFCs). CFCs are ozone-depleting and only very specific recyclers can deal with them appropriately.
If you are purchasing a new unit, check to see if your new supplier will take back the old one.
Suppliers must take back freezers in:
EU (EU Waste Electronics [WEEE] regulations).
Other
Don’t place fridges and freezers right up against the wall. Heat needs to be able to escape from the back to allow for efficient heat transfer.
Don’t forget to reuse (or share) racking from old units.
Participate in the International Freezer Challenge
Switching out for New
Without a full LCA, in general, it’s more sustainable to continue using equipment until it fails before replacing. This is because the production, shipping and refrigerants used in that old freezer have a significant carbon foot print that usually exceeds the carbon footprint of the extra energy use - especially if your lab uses electricity from renewable sources already.
But energy saving technology has indeed really improved over the years a 2007 ULT freezers uses 50% more energy than newer 2014 ULT freezers. It’s something to consider.
Liquid Nitrogen Cell Storage
Minimize the amount of time the door is open - Have a clear inventory of what is being stored.
- store the most frequently accessed samples on the top rack
Do an annual clear out - Think carefully about what items really need to be stored here.
Share with other labs - Minimize the number of Liquid Nitrogen storage units
Downsize - Larger units are more efficient, but oversized is a waste. Get the smallest unit that fits your needs.
Maintenance - Check the seals regularly
Dry Ice Alternative
Try using metallic beads (for dry waterbaths) or aquarium pebble gravel. Cool them in your ULT freezer (or store them there if you have room). The freezing rate was found to be a little faster than dry ice.
Source: nihms-667350.pdf (1.2 MB)
Heading 1
Heading 2
Heading 3
This article is a stub. You can help by expanding it. Get Involved!