The bags of frozen veg that sit in your freezer may have come from far-flung locations, transported through a lengthy cold chain that kept them at a consistently-low temperature of -18 °C. This number has become the global industry standard for freezing food. But now a report published for COP28 by a large team of international cold chain experts suggests that -18 °C may be unnecessarily cold and energy-consuming for the purpose it serves.
In fact, they find that increasing the global set point by a mere three degrees could avoid emissions equivalent to the amount that 4 million cars produce each year.
Freezing food is a critical method to help feed a growing world population: in fact if we found a way to refrigerate the 12% of produce that is wasted annually and prevent its spoilage, that food alone would feed an estimated 1 billion more people. And yet cold chains are the ultimate climate catch-22. On the one hand, by preserving food, freezing prevents a large chunk of emissions that would result from fresh produce going bad and wasting away. On the other hand, freezing food consumes huge amounts of energy, and therefore contributes to global emissions itself.
According to Yosr Allounche, one of the report’s authors, the global -18 °C ‘set point’ for frozen produce is a somewhat random number, selected in the mid-20th century as an international standard. This temperature corresponds to 0 degrees Fahrenheit, so it was “probably a round, easy number to remember,” says Alllouche, who is director general of the International Institute of Refrigeration, an independent intergovernmental organization that draws together scientific and technical evidence on cooling. “However, it proved to be a safe temperature to store and provide quality food.”
But with this in mind, the question on the researchers’ mind was: do we really need cold chains to be, well…quite so cold? The summary report Allouche co-authored with colleagues, titled Three Degrees of Change, surveyed the beneficial consequences of increasing that temperature to -15 °C, as well as the costs of sticking with -18 °C.
Currently, freezing food at -18 °C means that worldwide cold chains consume 484 terawatt hours (TWh) per year, the authors say. To put that into context, one terawatt hour is equivalent to the annual electricity consumption of 150,000 people living in the EU. Bearing in mind a rising global population and the expansion of cold chains to more parts of the world, this energy consumption is expected to substantially grow.
How would that change if temperatures were curbed to -15 °C? With this increase, the industry could reduce energy consumption by 25 TWh per year, the report calculated. That’s equivalent to the electricity consumption of Kenya, twice over—a change that would avoid 17 metric tons of greenhouse gasses, which is about the same amount of emissions generated by 4 million cars. “Increasing frozen food temperature by 3 degrees represents a significant energy win,” Allouche says.
This relatively minimal temperature increase in cold chains would also offset the need for 11.4 gigawatts of new wind energy generation, costing $15 billion (the researchers assumed future energy generation is renewably-sourced) that would otherwise be needed to power expanding cold chains.
What’s more, Allouche explains that this lowered temperature poses no risk to food. “Food safety is not an issue from the moment food is stored below -12°C, as all microbial growth is inactivated.” Meanwhile the report notes that for every degree decrease below -12°C, energy consumption increases by 2-3%.
It therefore seems like a no-brainer to turn the dial up on global cold chain temperatures: it’s a small change that could deliver huge potential benefits. But, the researchers caution that we need further research, particularly into the nutritional quality of food under new temperature regimes, before we leap to make any big change.
Some studies already show that produce like spinach can maintain its nutritional quality at -15 °C for up to three months. But more data is needed for different produce types. Existing research also indicates that the way food is handled before it’s frozen can alter its quality at subzero temperatures, so Allouche noted that we need more investigation into which practices help to ensure the best possible produce in -15 °C frozen food.
With -18 °C so embedded in the global supply chain architecture, changing that temperature will require changing minds—and global policies. Allouche believes that international regulation this “is the only way to bring up a new international set point.” And such big decisions need research to convince policymakers to make the change.
That’s what Allouche and team will be working on next, as they build their research summary into a full report, to be published in September 2024. “These findings give good reasons for ‘3 degrees of change’ to be further explored,” Allouche says.
Allouche et. al. “Three Degrees Of Change: Frozen food in a Resilient and Sustainable Food System.” International Institute of Refrigeration; Centre for Sustainable Cooling. 2024.
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