Why Some Out-of-Season Imports Are Sustainable Anyway

The cleanest sustainability story is that local and seasonal always beats imported and out-of-season. The real picture is more nuanced. Some out-of-season imports are quietly more sustainable than their hothouse local equivalents, and being honest about that makes the conversation more useful rather than less. It also stops shoppers making swaps that feel virtuous but change very little, while missing the ones that genuinely matter.

Local does not always win

Growing tomatoes in the depths of winter in a cold country usually means heating a greenhouse, and that warmth has to come from somewhere. A tomato raised this way can carry a heavier carbon footprint than one grown outdoors in a sunnier region and moved across a border by lorry or ship. The word “local” describes distance, not method, and method is often where most of the energy goes. When you buy a pale February tomato from a heated glasshouse a few miles away, the short journey home is doing very little to offset the fuel burned to grow it. The same logic applies to peppers, cucumbers and soft salad leaves, all of which sulk in cold soil and tend to be raised under glass or plastic when grown locally out of season.

It helps to picture where the energy actually goes. A heated glasshouse has to hold a summer climate against a winter outside, night after night, for the whole life of the crop, and the boiler runs whether the harvest turns out large or small. A field in a warmer region borrows that heat from the sun at no cost, then spends energy only once, on the trip north. Set the same tomato side by side, one grown under glass close to home and one grown in open ground far to the south and shipped, and the surprising winner is often the traveller. Distance is printed on the label and easy to worry about; the heating that dominates the footprint is invisible, and so it tends to be ignored.

The comparison that actually matters

For any given dish there are usually three honest options: in-season local, out-of-season local (typically greenhouse-grown), and out-of-season imported (typically from a warmer but not tropical climate). The common mistake is to compare only the first and the third, then declare local the winner and stop thinking. The more useful comparison is the second against the third. For many vegetables the out-of-season import beats the out-of-season greenhouse on energy, on footprint and often on flavour, because the sun has done the work the greenhouse boiler would otherwise have to do. Only for a narrow band of produce, mainly air-freighted items, does the import slide into being the worst of the three.

Air freight is the real outlier

Most of the worry about food miles quietly falls away once you know how the food actually travelled. Produce that arrives by sea or by land carries a small per-portion transport footprint, even across long distances, because a single vessel or lorry moves an enormous quantity in one trip. Air freight is the genuine exception, with a footprint far above the sea-shipped equivalent. The honest target, then, is not imports in general but air freight in particular. Volume is almost a red herring here: a whole container ship of bananas works out to very little per banana, while a small tray of flown-in herbs carries a heavy load per gram. The mode of transport matters far more than the quantity.

How to spot the flown-in items

Spotting air freight is easier than it first looks. Highly perishable produce sent fresh over long distances, such as berries from the other side of the world, fresh tropical leaves and delicate soft herbs, is the classic signature, because such things would spoil on a slow boat and so must fly. Hardier produce such as citrus, apples and root vegetables, along with anything frozen, almost never flies. Storage life is a reliable proxy: if a fresh item could not survive several weeks in transit, and it has clearly come a very long way, it most likely came by plane. Checking the country of origin on the label, then asking whether that item could plausibly travel slowly, will answer the question more often than not.

A few habits turn this into a quick check at the shelf. Read the country of origin first, then weigh it against the calendar: a fragile summer fruit sold fresh in the middle of winter, from a country on the far side of the planet, is the strongest hint of a flight. Note the texture and shelf life too, because a berry or a soft herb that bruises in the punnet is exactly the sort of thing that cannot afford weeks at sea. When the same fruit is offered both fresh and frozen, the frozen version has almost certainly travelled by boat or lorry, since freezing removes the race against spoilage that forces the fresh one onto a plane. None of this needs a footprint calculator, just the label and a moment’s thought.

The frozen, tinned and dried advantage

When out-of-season eating is unavoidable, the processed forms are usually the quiet winners. Frozen produce is picked at its peak, frozen quickly and then moved by sea or land, and for most fruit and vegetables it is the lowest-impact way to eat them out of season. Frozen berries in winter beat fresh berries flown across the planet on almost every measure that counts, including price and, often, nutrition. The one condition is a freezer that actually holds its temperature: keep it at 0F (-18C), as the US cold food storage guidance advises, and frozen produce holds its quality and its nutrients well through the winter rather than slowly degrading.

The same guidance is worth following for the rest of the cold chain at home, because a freezer is only as good as the fridge and the worktop around it. Keep the refrigerator at 40F (4C) or below, so that the fresh imports you do buy last as long as they can. Treat cooked leftovers as good for 3 to 4 days in the fridge, which is often what stands between a batch of cooking and a binned second helping. And do not let perishable food sit out at room temperature for more than two hours, or more than one hour when the kitchen is above 90F. These are dull numbers, but they are the difference between a kitchen that stretches a shopping trip and one that quietly leaks it.

Tinned and dried foods deserve the same defence. Tinned tomatoes, dried beans and lentils, tinned fish: all are shelf-stable, low-impact ways to eat foods outside their growing season, and the processing is not a sustainability failure but a piece of quiet infrastructure that has served kitchens well for generations. One point worth clearing up is the date stamp, which puts many people off perfectly good tins and packets. On most foods that date is a quality guide, not a safety deadline. Except for infant formula, these labels are not even required by law, and a “best if used by” date marks flavour rather than danger, according to the USDA guidance on food product dating. A tin a little past its date, with no bulging, leaking or off smell, is almost always fine to eat, which means fewer shelf-stable staples end up needlessly binned.

The honest catch of packaging

There is one fair objection to leaning on tins, jars and freezer bags, which is that all of them arrive wrapped. Containers and packaging are the single largest category of municipal solid waste, making up about 28 percent of what is generated, according to the US Environmental Protection Agency. That is not a footnote, and it deserves taking seriously. The resolution is not to pretend the packaging is free, but to keep it in proportion. Steel tins and glass jars are among the most widely recycled materials there are, and both can go round again without losing quality. A thrown-away portion of food, by contrast, carries the footprint of everything that went into growing, moving and chilling it, which usually outweighs the wrapper it came in. Buying the loose fresh import and letting half of it rot is rarely the greener choice just because it dodged a tin. The sensible reading is to prefer packaging that recycles cleanly and judge the wrapper against the far larger cost of wasting the food inside it.

Do not let waste undo the maths

There is a much bigger lever sitting behind all of this. The transport savings from any clever shopping choice are wiped out the moment the food is thrown away uneaten, and home kitchens are where most of that loss happens. Households account for around 60 percent of all food wasted worldwide, roughly 631 million tonnes in 2022, according to the UN Food Waste Index Report. That works out at about 79 kilograms of food per person each year, and, taken together, close to 1 billion meals are thrown out across the world every single day. Set against numbers like those, the gap between a shipped import and a greenhouse tomato is small.

Frozen, tinned and dried foods have a further quiet advantage here: they wait patiently in the cupboard or freezer, they do not demand to be cooked by Thursday, and they let you use exactly the portion you need and no more. Choosing the longer-lived version of a food is often a larger sustainability decision than agonising over where it was grown. A bag of frozen peas opened a handful at a time sidesteps the slow spoilage that turns a virtuous fresh purchase into landfill by the weekend.

A sensible order for out-of-season eating

None of this overturns seasonal eating, which remains the simplest and mostly correct rule of thumb. It just adds a sensible order for the times when out-of-season eating is going to happen anyway. Reach first for frozen, tinned or dried versions. Reach second for fresh imports that travelled by sea or land. Reach third for local greenhouse produce. Leave air-freighted fresh items for last, kept for the rare occasions when freshness genuinely cannot be substituted.

Kept in that order, the categories stop blurring into one another. You need not feel guilty about a winter avocado from a sunnier region that arrived by ship, and you might reasonably think twice about a tray of flown-in summer berries in January. Treating the two as morally equivalent leads to wrong decisions in both directions: passing up the reasonable import out of a vague unease, then reaching for the costly one because it looked no different. A flexible ladder like this quietly builds a more sustainable kitchen than a strict no-imports rule ever could, and it asks less willpower to maintain.