Food waste has a surprising impact on climate change

Each year, hundreds of millions of tons of food never make it from the kitchen – or grocery shelf – to the table. Instead, they end up in landfills, where rotting lettuce leaves and stale bread emit methane, a greenhouse gas roughly 28 times more powerful than carbon dioxide at trapping heat.

According to the United Nations, food waste now accounts for up to 10 percent of global greenhouse gas emissions – more than the entire aviation sector. If wasted food were its own nation, it would trail only China and the United States in annual climate pollution.

Food waste and climate repercussions

Robert Sanders, an assistant professor of marketing and analytics at the University of California San Diego’s Rady School of Management, has spent the last decade examining why so much edible food goes to waste and how policy interventions can bend the curve.

In a recent interview, Professor Sanders argued that trimming food waste may be the single fastest, most cost‑effective way to curb climate repercussions.

“It is nearly impossible for the globe to meet emissions targets set forth by the Paris Accords without reducing waste from the food system,” he warned.

Food waste: Hiding in plain sight

Although lawmakers and the public often focus on tailpipes and smokestacks, Sanders points out that the leftovers scraped off dinner plates or the strawberries that spoil in grocery back rooms punch far above their weight.

The methane produced as they decompose lingers in the atmosphere for about a decade but delivers an intense burst of warming during that period, making short‑term action on food waste a potent lever for averting near‑term climate tipping points.

“Reducing food waste is pretty much the most actionable measure humanity can take to mitigate greenhouse gas emissions in the short and medium term,” he noted. Yet when Professor Sanders first surveyed academic literature, he found a puzzling gap.

Policymakers were proposing rules to standardize expiration‑date labels, nonprofits were urging composting mandates, and states were drafting landfill bans – all based on assumptions that lacked rigorous field evidence.

That knowledge vacuum, he said, motivated him to run controlled experiments in real grocery aisles and back‑of‑house storerooms, tracking how shoppers and retailers actually behave when incentives change.

Good intentions, limited results

One headline solution embraced by several U.S. states is the food‑waste landfill ban. In theory, prohibiting retailers from tossing unsold produce or expired milk forces businesses either to donate surplus food, send it to anaerobic digesters, or pay composting facilities instead of dumping it.

In practice, Sanders’ research, conducted with colleagues at multiple universities, shows uneven results.

“My co-authors and I investigated the efficacy of the first five food-waste bans in the United States, and we found that only one state, Massachusetts, has been successful at diverting food waste away from landfills,” said Professor Sanders.

The reason appears twofold: enforcement and infrastructure. Massachusetts imposes clearer, better‑publicized penalties.

Additionally, the state offers businesses a robust network of composting centers willing to accept spoiled goods. Elsewhere, minimal fines and scarce processing facilities make compliance optional.

Dynamic pricing: Matching supply and demand

If strict bans are a blunt instrument, Sanders argues that pricing algorithms offer a finer scalpel. Roughly a tenth of all wasted food is chucked by retailers because perishables pass their sell‑by date still sitting on the shelf.

Shoppers routinely pay the same sticker price for milk expiring tomorrow as for jugs good for another two weeks, so predictable spoilage is baked into store margins. Sanders’ field studies suggest a market‑based alternative: dynamic markdowns.

By feeding inventory data, expiration horizons, and historical demand into a computer model, a grocery chain can automatically lower prices on soon‑to‑expire yogurt or ground beef several times a day. This nudges bargain‑hunters to snap up aging stock before it goes bad.

The benefits compound: less landfill methane, lower operating costs for stores, and cheaper staples – often fresher and less processed – for budget‑conscious customers.

“To an economist, it’s actually really weird that grocery stores don’t dynamically price their perishables,” Sanders observed. “Why should you, the consumer, be paying the same price for milk that will expire one week from now as you would for milk expiring three weeks from now? Not only is it unfair, it’s inefficient.”

Label confusion: An unproven culprit

Industry groups and some legislators have long asserted that ambiguous date stamps – “best by,” “sell by,” and “use by” – drive shoppers to bin perfectly edible food. California recently passed AB 660, mandating standardized phrasing meant to reassure consumers.

Yet Sanders cautions that no large‑scale, real‑world experiment has demonstrated the strategy’s effectiveness. “There’s still no scientific evidence of how these date-label formats actually affect purchases and waste in the field – that is, when real choices are made,” he said.

Until randomized trials produce hard numbers on consumer behavior, he ranks uniform labeling lower on the priority list than measures that directly raise disposal costs or reward timely purchasing decisions.

Household food waste habits matter

While systemic fixes target upstream inefficiencies, Sanders said everyday eaters remain the final link in the waste chain. Composting food scraps is helpful, but prevention trumps recycling.

He advocates meal planning, accurate head counts for events, and reminding yourself to eat leftovers long before they become science projects. In California, where municipalities now provide curbside green bins, he urges residents to keep those organic carts in regular rotation.

“Composting is better than sending food to landfills, but it’s best not to create food waste to begin with,” he said.

Funding the science

Sanders’ investigations into how consumers make expiry‑date decisions recently hit a roadblock when cuts to federal climate‑research budgets stalled a National Science Foundation grant.

The project would have generated large data sets on purchasing patterns in response to markdowns tied to shelf life – information the USDA and FDA have explicitly requested.

In the meantime, he and his collaborators are scouting alternative funding to improve food waste, underscoring the broader challenge of studying pragmatic climate solutions in an era of tightened purse strings.

Chipping away at a massive issue

Momentum is building: grocery giants in Europe have rolled out dynamic‑discount apps, while startups in the United States pilot real‑time pricing software for deli counters and bakery racks.

Policymakers, however, still debate whether to expand landfill bans or subsidize compost facilities without proof of impact.

Professor Sanders believes the fastest progress will come from connecting rigorous field experiments with scalable technology. Only then, he contends, will the world chip away at a problem large enough to rival the emissions of the aviation industry.

Until that happens, methane will keep seeping from landfills – one wilted lettuce leaf and one expired gallon of milk at a time.

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