DAILY SCIENCE

Researchers tested 72 ways to get groceries to your doorstep. So which is most climate-friendly?

Spoiler: All of the home delivery options had lower emissions than in-store shopping using an internal-combustion vehicle
November 29, 2022

Grocery delivery is associated with lower carbon emissions than in-store shopping, according to a new analysis. The findings suggest that some of the changes to grocery stores and shopping habits spurred by the COVID-19 pandemic also have the potential to be good for the climate. But strategies borne of old-fashioned frugality can help too.

The new results are in line with past studies that have shown that various delivery options have a smaller carbon footprint than in-store shopping. But many of those previous studies have been about general retail, not grocery shopping specifically. And grocery-specific studies haven’t included all of the steps involved in e-commerce or evaluated all of the options for so-called last-mile transport.

In the new study, researchers calculated the greenhouse gas emissions associated with getting a 36-item grocery order (the average size of online orders) from a grocery warehouse to a customer’s residence. They tested a total of 72 different pathways with 28 last-mile transportation options, including 10 home delivery, 6 in-store, and 12 curbside pickup options.

The new study includes the emissions from moving goods between locations (including by refrigerated transport), as well as from lighting, refrigeration, and other energy needed to run stores and micro-fulfillment centers—small, automated, in-store warehouses that some grocery chains have begun to set up in response to the COVID-era surge in online ordering.

Among the pathways the researchers investigated, the classic grocery shopping scenario—driving a gasoline vehicle to shop in-store—has a relatively large climate impact. Not surprisingly, driving an electric vehicle instead shrinks the carbon footprint.

 

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Curbside pickup of groceries picked from a micro-fulfillment center is also associated with lower emissions than in-store shopping, because these facilities are more compact and energy-efficient to run than retail stores, the researchers report in the journal Environmental Science & Technology.

And having groceries delivered is also more climate-friendly than driving to the store to get them. The findings point to the importance of last-mile transportation as the dominant contributor to the carbon footprint of grocery shopping, the researchers say.

“If you own a gasoline powered vehicle, home delivery is a better option in urban areas,” says study team member Greg Keoleian, director of the Center for Sustainable Systems at the University of Michigan in Ann Arbor. “If you live in a rural area, home delivery may not lead to energy or carbon reduction depending on the delivery route and vehicle,” he adds.

Grocery delivery tends to save on carbon emissions because a single vehicle can take the most efficient route to deliver orders to multiple households. Along the same lines, an individual can reduce the impact of grocery shopping by combining trips. The scenario modeled in the study, which assumes a person stopping by the grocery store on the way home from work, halves the carbon emissions of the shopping trip.

Similarly, shopping half as frequently reduces emissions by almost half, the researchers found. The same principle applies to getting groceries delivered: delivering more items in a single trip rather than half as many in two trips is more climate-friendly—although stocking up too much can also contribute to food waste, the researchers acknowledge.

Meanwhile, those special trips to pick up a single forgotten item have a massive climate impact: “a refrigerated item has 96% lower emissions if purchased as part of the 36-item basket than if purchased alone,” the researchers write.

Overall, the results highlight the importance of meal planning, grocery list making, and planning ahead to reduce the number of driving trips, Keoleian says.

The researchers also investigated the impact of emerging delivery technologies such as robotic vehicles that can deliver four grocery orders over a 10-mile route, sidewalk robots that can deliver a single grocery order with a four-mile route, and drones to deliver single items. For customers who live within two miles of a grocery store, the sidewalk robot is the most carbon-efficient delivery option, and the drone is the most efficient option for delivery of a single item.

The team is investigating the climate impact of other aspects of the food system, including reusable versus single-use restaurant takeout containers, Keoleian reports.

Source: Kemp N.J. et al.  “Carbon footprint of alternative grocery shopping and transportation options from retail distribution centers to customer.” Enivronmental Science & Technology 2022.

Image: ©Shutterstock/rblfmr

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