Ordering items for delivery from the local store may help customers minimize their carbon footprints.

Computer simulations of shopping trips and deliveries in the United Kingdom allowed researchers to estimate the carbon emissions associated with each item purchased through different means. On average, deliveries by a local shop resulted in less than half as much carbon dioxide being emitted per item as deliveries by online-only retailers, which deliver items through package distribution centers, researchers report online February 26 in Environmental Science & Technology. Local deliveries also boasted lower emissions than in-person shopping.

Environmental scientist Sadegh Shahmohammadi and colleagues simulated thousands of instances of someone purchasing a cartful of items, such as personal care and houseware products, either in-person or online. To reflect real-world shopping and delivery conditions, the team factored in emissions estimates for activities such as powering storage warehouses, transporting items in different types of vehicles and walking versus driving to a store.

Greenhouse gas emissions associated with local store deliveries averaged about 0.07 kilograms of CO 2 per item, compared with 0.18 kilograms for orders from online retailers and 0.1 kilograms for in-person shopping.

Deliveries by local shops tend to be greener than those from online retailers because people ordering from a single store usually buy a bunch of stuff at once, explains Shahmohammadi, who worked on the research while at Radboud University Nijmegen in the Netherlands. Online retail shoppers, on the other hand, often get items delivered piecemeal — racking up a higher carbon footprint over multiple deliveries.

Bundling items for single delivery could help online shoppers curb their carbon emissions, the authors say. Meanwhile, in-person shoppers can shrink their footprints by looping supermarket trips in with other errands, or by biking to the shop instead of driving.