The energy we eat

Fertilizers, machinery, processing, refrigeration, transport, cooking and waste.

Before you cook, a lot of energy already happened

The kitchen is the visible stretch of a much longer chain

When someone lights the stove to cook, that is only the final stage, and often a fairly small one, of an energy chain that began much earlier and in very different places. The nitrogen fertilizers that made much of modern agriculture possible are manufactured from natural gas, which acts simultaneously as chemical feedstock and as the energy source for the process. Tractors and irrigation systems consume fuel or electricity directly in the field itself. After harvest, greenhouses, industrial processing plants, cold-storage chambers that maintain the cold chain, packaging that protects the product during transport, and ships, trains or trucks that move it to the point of sale all consume additional energy at every stage, on top of needing to maintain food-safety conditions throughout the journey.

Transport is not always the factor that weighs the most

There is a very widespread intuition that the distance a food has traveled — so-called "food miles" — is the most important environmental factor when choosing what to buy. The available evidence does not generally support that intuition: large-scale lifecycle analyses, such as Poore and Nemecek's 2018 study, estimate that transport accounts, on global average, for around 6% of a food's total carbon footprint, while agricultural production itself and the associated land-use change usually weigh considerably more. This does not mean transport is irrelevant in every case: products regularly flown by air, or supply chains with particularly high losses, do add a significant energy cost. But as a general rule, what you eat matters far more than where it comes from, because the vast majority of long-distance food transport happens by ship, a comparatively efficient mode of transport per tonne carried.

Cutting waste saves the whole chain, not just the cooking

At home, covering a pot while it boils, matching the flame size to the actual size of the pan, using a pressure cooker or microwave when the final result allows it, and cooking several portions at once instead of repeating the process several times all genuinely, if modestly, reduce the energy consumed in the cooking itself. But avoiding throwing away a meal that has already been fully prepared has a much larger effect, because that waste does not only lose the cost of having cooked it: it also irrecoverably loses all the energy invested in growing, processing, transporting and preserving that food at every earlier stage of the full chain.

A sustainable diet also has to feed the person following it

No global figure for a food's environmental impact should, without further nuance, become an individual medical prescription: each specific person's health, their food culture, their real access to different foods, and their territory's agricultural conditions matter as much as the average environmental-impact figure. That said, some decisions are robust across most reasonable contexts: reducing the waste of food already produced, moderating consumption of the highest-average-impact products without necessarily eliminating them entirely, taking advantage of locally available seasonal produce, and properly storing food so it lasts longer in good condition are decisions that almost always reduce real energy and environmental cost without compromising the nutrition of whoever adopts them.

What really matters

  • Avoid waste before anything else: throwing away a meal already prepared loses the entire energy chain invested in producing it, not just the cost of cooking it.
  • "What" matters more than "where from": transport is usually a small fraction of a food's total footprint; agricultural production and land-use change weigh more in most cases.
  • Take advantage of the season and store food well: it reduces the need for prolonged cold chains and out-of-season transport.
  • Moderate, don't ban by decree: the highest-average-impact products don't have to disappear entirely from a reasonable diet; moderating their consumption already reduces impact substantially.
  • In the kitchen: cover the pot, match the flame size, use pressure cooking or the microwave when the result allows it, and cook several portions at once.

Don't turn a global figure into a medical prescription

Individual health, food culture, real access to food, and a territory's agricultural conditions matter as much as any environmental-impact average. These priorities are robust across most contexts, not a universal mandate.

The numbers, with their source

A third of the food produced in the world is lost or wasted

According to a study commissioned by the FAO, roughly a third of the food produced worldwide for human consumption — on the order of 1.3 billion tonnes a year — is lost or wasted somewhere along the chain. More recent data from UNEP and the FAO break that figure down: 13% of the world's food is lost in the supply chain before reaching the consumer, and a further 19% is wasted at the retail, food-service and household stages. In 2022, around 1.05 billion tonnes of food were wasted while 783 million people went hungry.

Sources: FAO — Cutting food waste to feed the world; World Resources Institute — How Much Food Does the World Really Waste?.

Food waste, almost five times aviation's emissions

Food loss and waste account for between 8% and 10% of global greenhouse gas emissions every year, almost five times the total emissions from the aviation sector, with an estimated economic cost of one trillion dollars a year.

Source: UNFCCC — Food loss and waste account for 8-10% of annual global greenhouse gas emissions.

Transport, only around 6% of a food's average footprint

Poore and Nemecek's (2018) lifecycle analysis, covering nearly 40,000 farms in 119 countries, estimates that transport accounts, on global average, for around 6% of a food's total carbon footprint — far behind agricultural production and land-use change, which usually dominate the final result.

Source: Our World in Data — Food choice vs. eating local.

What this table is missing

These figures are global averages; a specific product routinely flown by air, or a local supply chain with particularly high losses from inadequate refrigeration, can completely reverse these general proportions for that specific case.

Sources