The most detailed life cycle analysis of food waste ever offers eye-popping revelations

2023-03-24

Food loss and waste contributes half of the annual emissions arising from the whole global food system. This enormous figure was recently revealed in a Nature Food study—which, among other revelations, highlighted the role of just four nations in generating almost half that amount, along with the surprisingly high emissions toll of lentils and wheat.

Several studies have drawn up estimates of food system emissions. But this study provides the most holistic and thorough estimate of food loss and waste emissions to date.

To get there, the study authors mapped the emissions associated with any food loss or waste across nine lifecycle stages in 2017, spanning food’s journey from farm to plate (or bin). They did this at the country level, and looked at four major food groups containing 54 types of food.

First of all, this revealed a staggering 9.3 gigatons of carbon dioxide-equivalent associated with food loss and waste: that’s around half the total gob of carbon released by the global food system each year. It’s also double the estimates made in previous research.

Digging into this considerable figure produced a wealth of insights. Firstly, the so-called ‘supply-embodied emissions’ of food—emissions linked to unintentional food loss or wastage on the farm, during storage, transport, processing, retail, and in the final stages of food consumption—generated around 6 of those 9 gigatons in 2017. That’s a huge share, equivalent to two months-worth of emissions generated by burning fossil fuels.

Food transport and processing associated with lost or wasted food are major sources. But in particular, the researchers highlight the impact at the consumer stage, which generates 35% of those embodied emissions. That’s more than from the wholesale, trading, and retail stages combined, which contributed 11%. In fact, reducing just one-third of the consumer-stage emissions in China and the United States would be comparable to the emissions produced during the processing and transport stages of the food system globally, the researchers calculate.

The remainder of food loss and waste emissions—2.84 gigatons of CO2-equivalent, or about one-third—occur at the end-of-life stage, which comes down to how the wasted food is disposed of, and how well it’s managed after that.

Looking at the lifecycle is just one way to visualize where emissions occur: this is also influenced by food type. Meat, as might be expected, had a far greater overall emissions impact than plant-based foods when lost or wasted, largely due to the higher impact of production at the farm stage. Yet, this didn’t hold across all lifecycle stages. In fact, rather surprisingly, cereals and pulses like lentils and wheat accounted for the largest share—up to 75%—of all emissions when wasted or lost at the end-of-life stage.

That’s partly due to the large amount that’s consumed and therefore also wasted globally compared to meat, but also because these foods have a comparatively high carbohydrate content, which emits large amounts of carbon and methane.

Geography matters in this equation too. The study found that four nations—the United States, China, Brazil, and India—account for a whopping 44% of all supply-embodied emissions, and 38% of total emissions at end-of-life, mainly due to large populations and greater production and consumption or meat in these regions.

Socioeconomic factors and the degree of technological development also determine how much food gets wasted or lost in individual countries, or how it’s dealt with when it is. For example, more developed nations or those with a higher relative GDP may show reduced emissions on the end-of-life stage, because they’re better equipped with innovative technologies like anaerobic digestion to reduce and capture these emissions in place.

These facts and figures are just a sampling of the many discoveries that the study made, which is its strength: the detailed, comprehensive picture it paints of food loss and waste may help pinpoint where changes need to happen to bring emissions down, the researchers hope. At the very least, it reveals that there are many routes to action.

One broad brush measure could be to halve food waste and loss outright, which would cut 4.65 gigatons of CO2-equivalent emissions from the global picture each year, or a quarter of emissions from food prediction overall, they found. Interestingly, almost exactly the same amount could be cut by halving global meat consumption.

Significant, and perhaps in the short term more realistic, reductions could also be achieved by awareness-raising about food waste to reduce the huge contribution that consumers make. Or, by increasing the global spread of waste-management techniques like composting and anaerobic digestion. In fact, the study finds that a 50% increase in the market share of emissions-busting technologies would curtail food waste emissions by 15%.

The challenge is undoubtedly huge. But perhaps the study’s biggest takeaway is that this huge emissions problem is avoidable. With coordinated action, new technologies, and dietary flexibility, we may be able to turn food loss into a win.

Zhu et. al. “Cradle-to-grave emissions from food loss and waste represent half of total greenhouse gas emissions from food systems.” Nature Food. 2023.

Anthropocene, 24 March 2023
; https://www.anthropocenemagazine.org