Price Signals Cut the Carbon Footprint of Lunch

In February 2026, France published its National Strategy for Food, Nutrition and Climate, which calls for environmental labeling, support for collective dining and financial policies that make sustainable food more accessible. A field experiment at HEC Paris shows how differently those levers can work in practice. The clearest response came from the price tag. At the first price level that made low-carbon meals slightly cheaper than  high-carbon meals, the average carbon footprint per meal fell 26.8 percent.

A canteen becomes a policy laboratory

Yurii Handziuk and Stefano Lovo tracked the lunch choices of more than 4,000 students, staff and faculty members from August 2021 to June 2023. Their data covered nearly 140,000 meals and 81 main dishes. The HEC Paris canteen offered an unusually controlled setting: it is the main affordable lunch option on a campus located outside central Paris, purchases are recorded through individual cards, and anonymized identifiers allowed the researchers to follow individual choices over time.

The experiment compared three approaches. Carbon-footprint information was displayed beside each dish from November 21, 2022, with a colored grade, the kilograms of carbon dioxide equivalent per portion and a comparison with car travel. Red meat was removed from Thursday menus from September 2022. During four weeks in March and April 2023, the researchers also introduced a bonus-malus pricing system that discounted dishes below the median carbon footprint and raised prices above it.

To isolate the effects, the researchers compared behavior with the previous academic year and controlled for changes in the daily menu, weather, canteen attendance and wider online interest in the term “carbon footprint.” The same customers could therefore be observed before, during and after the different interventions.

The composition of the menu already shaped what people bought. A rise in the average carbon footprint of the dishes offered on a given day was associated with a roughly similar rise in the footprint of the meals purchased. The experiment therefore tested both sides of the choice: what the canteen made available and how customers responded to information and price.

Labels reached people, prices moved them

The information campaign was highly visible. In a follow-up survey, 88.65 percent of users said they had noticed the carbon-footprint information, 81.56 percent considered it reliable, and 98 percent of respondents correctly understood the basic meaning of the posters. Yet the labels produced no statistically significant reduction in the carbon footprint of the meals purchased.

That result contrasted sharply with an earlier online exercise involving 642 people from the same community. When participants chose from a hypothetical menu, adding carbon information reduced the footprint of their stated choices by about 30 percent. Their actual canteen purchases after the survey showed no comparable change. The field experiment captures the familiar gap between what people say they would choose and what they buy when taste, routine and price are present.

Concern about climate change did not identify a group that reacted more strongly. The researchers also found no stronger response among users who noticed the labels, trusted the information or reported greater patience about future outcomes. They interpret this pattern as consistent with consumers recognizing that one lunch has a negligible effect on global warming and choosing the dish they prefer.

The price relationship mattered

Before the experiment, menu prices were negatively correlated with carbon footprint: some of the most carbon-intensive dishes were also among the cheapest. The bonus-malus system reversed that relationship. Prices changed according to the distance between a dish’s footprint and the menu median of three kilograms of carbon dioxide equivalent per portion.

The first adjustment, valuing carbon at €0.10 per kilogram, brought prices and carbon footprints close to a neutral relationship and had no significant effect. Once the relationship became positive, choices shifted quickly. At €0.25 per kilogram, the average footprint fell 26.8 percent. It fell 32.9 percent at €0.50 and 42.6 percent at €1.00. Each time the original prices returned, customers reverted toward their earlier choices.

The posted menus made the trade-off concrete. In one example at the €0.25 level, a vegetarian plate with a footprint of 0.3 kilograms fell from €5.00 to €3.65, while beef balls with a footprint of 5.6 kilograms rose from €3.80 to €5.10. Consumers retained access to both meals, while the price ordering now matched the carbon ordering.

The policy also lowered what customers spent on average, because demand moved toward cheaper low-carbon dishes. Average spending per meal declined 4.2 percent at the €0.25 level, 7.1 percent at €0.50 and 32.8 percent at €1.00. The researchers estimate that the first effective setting cost the canteen about €0.21 for each kilogram of carbon dioxide equivalent avoided. The trial was designed to test behavior rather than balance the canteen budget.

A restriction changed meals and attendance

Removing red meat from Thursday menus produced a large change on the day itself. The average footprint of meals purchased on Thursdays fell 64.2 percent, or 2.1 kilograms of carbon dioxide equivalent per portion. Across the full week, the estimated reduction was between 10 and 12 percent.

Customers did not compensate by ordering more red meat on other weekdays. Thursday attendance, however, dropped 15 percent. The weekly estimate therefore depends on what absent diners ate elsewhere. The lower figure assumes they found their usual dishes outside the canteen; the higher figure assumes their replacement lunches were as low-carbon as those bought on campus.

The result shows both the power and the limit of restricting supply. A canteen can remove a high-carbon option and immediately change the meals it serves. Some customers may respond by leaving the setting where the policy applies.

People favored the policy that preserved choice

The follow-up survey tested whether the most effective intervention could also win support. After the findings were explained, 92.18 percent of respondents chose one of the two approaches that had reduced emissions: bonus-malus pricing or supply restrictions. Pricing was roughly twice as popular as removing red meat, and about two-thirds preferred it when asked to choose directly between the two.

That preference matched the flexibility built into the system. High-carbon dishes remained available, while customers paid more for them and less for low-carbon options. Carbon information also retained broad support: 93.26 percent wanted the footprint displayed, even though the field experiment found that labels alone did not change purchases.

Preferences also reflected existing diets. Respondents who favored doing nothing had chosen meals averaging 5.6 kilograms of carbon dioxide equivalent. The average footprints of those supporting bonus-malus pricing or the red-meat restriction were 21 percent and 18 percent lower, respectively. The result suggests that policy choices were connected to the personal costs and benefits respondents expected from each option.

The setting limits how far the results can be generalized. A university or company canteen can adjust relative prices while keeping customers because it offers convenience and subsidized value. A commercial restaurant acting alone could lose high-carbon customers to competitors. The authors see greater potential in collective dining and in products where the low-carbon alternative delivers a similar experience, such as electricity from renewable rather than fossil sources.

A budget-neutral version would require taxes on carbon-intensive choices to finance discounts on lower-carbon ones, or another mechanism that transfers the cost among consumers. Those proposals were outside the field test. Its central result is concrete: when the price ordering reflected the carbon ordering, people changed their lunch.