Does Grocery Delivery Really Cut Down on Emissions?

Recent study determined where the sustainability rubber meets the road
Lynn Petrak
Senior Editor
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Grocery Delivery Teaser
Researchers at Carnegie Mellon University found that the greatest emissions benefit is from ordering at the nearest grocery store.

As the e-comm business continues to come into its own, with some retailers changing their fulfillment models and others embracing new technologies to get products to consumers, a recent study shows that there is some wobbliness to the notion that online shopping is more efficient and sustainable than in-person shopping.

According to a study published earlier this summer in the journal Transportation Research, there are a large number of variables that undercut the assumption that having groceries delivered by a service that fulfills many orders in a day cuts down on emissions that would have been generated by more individuals traveling to retail locations.

[Read more: “SPECIAL REPORT: The Greener Grocer”]

Researchers at Carnegie Mellon University took many of those variables into consideration and determined that some delivery situations can reduce carbon dioxide emissions while other circumstances can lead to a notable increase in emissions over brick-and-mortar visits. In fact, it's the sheer number of scenarios that makes conclusions about the efficiencies of the digital space more unreliable.  For example, people often stop and pick up groceries on their way home from work, meaning that it isn’t necessarily a dedicated two-way grocery visit. And they don’t always go to the same store, depending on their tastes and time availability.

“It is possible that switching to online grocery shopping could potentially reduce the number cars on the road when delivery routes serve multiple homes, improving congestion and reducing emissions. However, this could also potentially lead to system-wide inefficiencies, exacerbating congestion and emissions within a region if it ultimately leads to more trips to and from grocery stores,” the researchers wrote.

The team at Carnegie Mellon used existing research and applied travel pattern data to a case study in Seattle, Wash., to gauge changes in peak hour congestions and emissions. through their demand modification process and traffic simulation process. They found that the start location of deliveries had the largest impact on emission and traffic and determined that the beneficial impact was greatest when groceries were delivered from a store closest to the consumer.

Substitution and batch size were other key factors. “The more substitution occurs, the more reductions in congestion, energy and emissions occur. Batch size also determines the level of impacts and has a non-linear effect. The majority of improvements occur when the batch size increases anywhere between 1 and 3, and after this we start to see diminishing returns,” the researchers noted.

Ultimately, switching to off-peak hours has a more positive effect on congestion and emissions, the study showed. That’s a choice that consumers can and often make, but simply having groceries delivered from the closest grocery store is a harder sell.

“Assigning delivery orders to the closest store to the customer is not the scheme that exists today, so we conclude that current online grocery delivery is likely increasing emissions, and perhaps also increasing congestion in Seattle if not enough deliveries get shifted to off-peak hours,” the group concluded. “The reason behind this is that most of the replaced trips in the case study were not dedicated grocery shopping tours, but were trips optimized by the customers themselves by adding them to their tours when on the road for something else.

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