Yesterday I was in the cornershop for a last minute addition to dinner. As I was rooting around amidst the frozen yorkshire puddings for some part-baked garlic bread, I was reminded of a niche climate campaign that I don’t think I’ve written about before: Move to -15.
Move to -15 is a coalition of partners in the frozen food sector who are campaigning for warmer freezers – or less cold freezers, to be more accurate. It is widely accepted that -18 to -23 centigrade is the optimal freezer temperature in the UK. If you have a freezer at home, it is likely within that range or slightly colder. So are the ones in the shops, and in the trucks delivering frozen items to them, and the warehouses they pick up from, and so on down the cold chain.
The -18 standard was set in the early days of refrigeration, almost a century ago. At the time, freezers were relatively primitive and slower to reach temperature. The supply chain itself was less developed. Despite a century of improvements in logistics and in technology, the standard is still -18C.
It doesn’t need to be. The freezing process begins at 0, and food remains stable and entirely safe at warmer temperatures. What matters more is the speed and efficiency of the moving and handling along the way. Inefficient logistics won’t deliver a stable product even at -18, whereas a well functioning system would be perfectly fine at -15.
That’s the argument that Move to -15 make, and there are multiple benefits to resetting the standard three degrees lower. That three degree cut in temperatures means less energy spent on electricity, saving money and cutting carbon emissions. Moving to -15 would save 5-7% of the energy use in the supply chain on average, 10-12% in some contexts. If that doesn’t sound like a huge amount, it’s worth remembering just how big the cold chain is across the globe. The global energy saving at -15 would be equivalent to twice the annual energy consumption of Kenya.
With a century of conventional wisdom mandating a minimum of -18, a lot of people will want to know if it’s safe to store food at -15. The industry knows this, and so Europe’s leading frozen food company, Nomad Foods, did a study recently. You might not recognise Nomad Foods, but you probably know their brands – Bird’s Eye, Findus or Iglo depending on where you are in Europe. They also own Goodfella’s pizza, and the Aunt Bessie’s I was digging through in the cornershop.
They studied a variety of foods at four different temperatures, from -9 to -18, and assessed any change in quality over time. None of the foods showed any deterioration at -15, and as a result Nomad have thrown their weight behind the Move to -15 campaign. Their support could make a big difference. It was Bird’s Eye that invented the flash freezing process in the first place. They have the most to lose if the industry were wrong, and so their support could well nudge anyone who was on the fence.
Would it be better to stick at -18, just to be on the safe side? No, because even -15 has three degrees of slack before you get any deterioration, and even then most items are entirely safe at -12. Minus 15 is actually the optimum, and -18 is over-freezing.
There is one sticking point however. While almost every food is fine at -15, ice cream is an exception and can crystalise in unpleasant fashion if it gets much warmer. There are a couple of ways around this. One is to keep ice cream freezers at a colder temperature, since they’re often in their own freezer anyway.
A more interesting idea is the one developed by Unilever. They created production methods that create ice cream that is stable at -12, and then gave away the research so that anyone can use the technique. If widely adopted, ice cream could stop being the problem child of the cold chain and lead the way on warmer freezers.
There’s a good chance that you won’t hear about this again for a while, if ever. Move to -15 is a business to business campaign. The idea is being discussed in industry journals and conferences. If it does get adopted, there will be a lot of people to convince and a long roll out. But maybe, one day in a few years time, I’ll be searching for garlic bread in an imperceptibly warmer freezer, and the world will be saving 17.7 million tonnes of CO2 a year at absolutely no cost.
The Earthbound Report 
I used to think that -18degC was scientifically established as optimum for freezers, until one day I realised that it is in fact merely 0degF.
In other words, despite looking as though -18degC is a carefully chosen value for freezers, it is just what looked good to users of the Fahrenheit scale.