Participate in the National Freezer Challenge 2025!

Introduction

Cold storage is essential in scientific research, but it also cases a high energy demand for laboratories. Ultra-low temperature (ULT) freezers operating at -80°C use about as much electricity as two average Dutch households. Freezers at -150°C or systems using liquid nitrogen consume even more. In addition, hospitals and research institutes have a large number of -20°C freezers, which also often use a lot of electricity.

During the National Freezer Challenge, action is taken to reduce CO₂ emissions and save costs. By cleaning out unnecessary or outdated samples, valuable storage capacity is freed up, reducing the need for new freezers. In addition, freezer contents can be consolidated, which in some cases may result in freezers being shut down.

On this page, you will find all the necessary information about the National Freezer Challenge 2025!

The National Freezer Challenge takes place at three levels:

Department

The Freezer Challenge participants clean out the freezers and keep track of how many boxes they have emptied using a scoring sheet. They share their results with a designated departmental coordinator from their department. This can be a lab coordinator, a local green team or an enthusiastic colleague that wants to coordinate this initiative locally. The departmental coordinators serve as the point of contact within the department for the challenge and will collect the results from staff members in their department via a Microsoft Forms form.

Institute

The institute coordinator collects the results from all departments within the participating institute and shares them with the national working group. The institute coordinator is also the point of contact within the institute for questions about the challenge. In addition, the institute coordinator determines the details of the challenge within the institute, for example, whether an internal prize will be awarded to the department that has shown the greatest commitment to the challenge.

National

The national working group of the Freezer Challenge, part of the NFU working group "Sustainable Laboratories", compiles all national results, which will be presented at the beginning of 2026. In addition, several clean-up initiatives from participating institutes will then be highlighted nationwide. Every UMC in the Netherlands is represented in this working group and already has an assigned institute coordinator. Do you not work in a UMC but would still like your institute to participate in the challenge? Then you can register your institute for participation via Green Labs NL using this link.

Participating Institutes

Would you like to participate in the Freezer challenge with your institute? Register your institute using this form

National Freezer Challenge Resources

Information for Participants

Communication material

All other required documents will be shared by your local Freezer Challenge coordinator

Frequently Asked Questions

About the Challenge

The National Freezer Challenge is an initiative that will start on September 1 within institutes in the Netherlands. The challenge is inspired by the international concept and aims to promote energy savings and sustainable freezer management in laboratories (Ref). The challenge is organized by the seven University Medical Centers (UMCs) in the Netherlands and Green Labs NL.

The challenge is organized by and for Dutch UMCs, together with the NFU sustainability working group and Green Labs NL.

Yes, absolutely! You can register your institute for the National Freezer Challenge via this form. Has your institute already communicated about the Freezer Challenge internally? Then registration via Green Labs NL is no longer necessary. Contact your institute's Freezer Challenge contact person for more information about participation.

To promote:

  • Awareness and insight into the energy consumption of laboratory freezers.
  • Cleaning out unnecessary samples.
  • More efficient use of freezer capacity, possibly leading to reorganization and the shutdown of freezers.

As a departmental coordinator, you compile the questionnaires filled in by colleagues in your department. This gives you an overview of the freed-up space and which freezers contain a lot of empty storage capacity. The questionnaire is already created in Microsoft Forms and can be distributed within your department by email.
At the end of the challenge (December 31, 2025), you add up the results of all participants in your department and send them to the institute coordinator. A separate questionnaire will be shared later in December, allowing you as a department coordinator to easily share the results. These include:

  • The number of participants in your department
  • The number of cleaned-out boxes and samples
  • The number of freezers set at -70°C

In addition, as a departmental coordinator, you will have an overview of which freezers are largely empty. It will be your task (together with your colleagues) to consolidate freezer contents where possible, so that freezers can be (temporarily) switched off.

Each UMC automatically participates in the challenge and already has a designated institute coordinator, who is the central contact within the organization for the challenge. This person receives all necessary information from the national working group to set up the challenge.

Other hospitals and institutes that want to participate can appoint their own institute coordinator and register via this link.

Within your department, appoint one or more people to coordinate the challenge (the department coordinator). This could be a lab manager, the local green team, or an enthusiastic colleague who wants to contribute at the departmental level.

This person will receive all the practical tools to set up the challenge within your department, including manuals, communication materials, and a questionnaire to collect the results of the clean-up initiative.

Everyone can then individually clean up their freezers and keep track of how much space has been freed. You have until the end of the year to do this. We supply an optional scoring sheet that you may use to keep track of the amount of space you free up. Make sure you share your clean-up results via the questionnaire before December 31.

The answers to the questionnaire are collected by the departmental coordinator, aggregated, and then forwarded to the institute coordinator.

No, there will be no official winner. However, honorable mentions will be given to departments or institutes with inspiring or innovative contributions. If your institute does want to award a prize internally to the department that has cleaned out the most, that is of course possible. This can be arranged internally by the institute coordinator.

Date

 Activity

1 September

Start National Freezer Challenge (registration possible)
31 December

Deadline for submitting the results of participants to department coordinators

The Freezer Challenge is a practical tool for complying with the new ISO 15189:2022. The standard requires a risk-based approach: materials may be disposed of when the risk of negative impact is low or nonexistent. Furthermore, the standard emphasizes sustainable resource management and strict adherence to retention periods—no longer storing prevents wasted freezer capacity and energy. The Freezer Challenge fully ensures this: disposal is carried out according to policy, with traceable disposal and documented accountability steps. Participation not only strengthens quality and compliance but also contributes to sustainability and the efficient use of laboratory resources.

To further support participants, the national working group has developed a risk analysis for the Freezer Challenge. This demonstrates that disposal is fully compliant with ISO 15189:2022.

About the Sustainable Use of Freezers

A ULT at -80°C consumes on average 4000–7000 kWh per year, comparable to two to three average households in the Netherlands. Freezers set at higher temperatures can also use a lot of electricity, and within larger institutes there are sometimes hundreds of freezers in lab departments. In addition, freezer energy consumption increases due to:

  • Poor organization of freezer content or lack of an inventory, resulting in the freezer door staying open longer.
  • Frequent door opening.
  • Poor placement – too close to a wall or other equipment, and insufficient ventilation.
  • Poor maintenance (defective seals, dust in condenser grid/filter).

Yes, more and more organizations are setting their ULT freezers to -70°C instead of -80°C. This results in an average electricity saving of 28% per freezer (Ref). In the past, all freezers were set to -70°C, but around the year 2000, when freezers became capable of reaching lower temperatures, -80°C was adopted as the new standard. Increasingly, laboratories are switching back to -70°C to reduce labs' footprint. Scientists record in this database how long different samples are stored at -70°C. In some cases, samples have been stored successfully at -70°C for over 10 years without issues. In addition, companies are also adopting -70°C as the new recommended storage temperature for their products.
Please note: Always check whether this is permitted within your protocols and research frameworks.

 

The difference is actually minimal. Warming up to -20°C from -70°C takes about 19 hours. From -80°C, it takes 30–60 minutes longer depending on the location in the freezer where it is measured, with a total of 19.5 hours (Ref). The difference in warming up until -50°C is also minimal.

 A good registration system (such as a LIMS or Excel) provides:

  • Insight into which samples are still needed and should be kept.
  • Insight into ownership of samples and opportunities for cleanup, e.g., when redundant samples are present or colleagues leave.
  • An overview of samples, which makes searching convenient and prevents the door from having to be opened repeatedly or for a long time.
  • Efficient use of freezer space.
  • Avoidance of duplicate storage or unnecessary freezer expansion.

  • Discuss with the owner or responsible researcher whether storage is still needed. If they are no longer employed, consult with the manager or department head.
  • It can help to provide concrete numbers: how many samples are involved? You can also calculate the impact of those samples by dividing the freezer's energy consumption by the volume of stored samples.
  • Handle according to retention periods or ethical guidelines.
    • For research that does not fall under WMO legislation (in Dutch: Wet medisch-wetenschappelijk onderzoek met mensen), there are no legally established retention periods (Ref).
    • Different retention periods have been agreed for diagnostic samples for each expertise.  
      • See the Association for Clinical Genetic Laboratory Diagnostics (VKGL) guidelines here (in Dutch).
      • See the guidelines of the Dutch Association for Pathology (NVVP) here (in Dutch).
      • The Dutch Association for Clinical Chemistry and Laboratory Medicine (NVKC) is currently busy drawing up recommendations/guidelines.
  • Document and dispose of samples safely.

Consider joint cleanup actions as a team or department, such as the National Freezer Challenge.

  • Lower energy consumption = reduced CO₂ emissions.
  • Lower maintenance and repair costs.
  • Better use of space and resources, allowing freezers to be shut down. See, for example, this post!
  • Increased awareness and collaboration within teams.

 Yes, check out the information below:

People working on this project

Joep Sprangers
UMC Utrecht
Aram de Haas
Amsterdam UMC
Mandy Erkelens
Leiden UMC
Esmee Kiewiet-Kasteleijn
Erasmus MC Rotterdam
Fred van Opzeeland
Radboud UMC Nijmegen
Anouk de Boer-Poelstra & Megha Pandey-Upadhyay
UMC Groningen
And with support from all other members of the National NFU working group 'Sustainable Laboratories'