But staying aloft for long with a heavy load is energy-intensive. Drones could be combined with trucks that drive to local transport nodes, and then hand over to drones for the last mile.

Or perhaps ground-based robots? This year, both FedEx and Amazon announced plans to deploy these smart, autonomous hampers-on-wheels along our sidewalks, dodging pedestrians and crossing at the lights. Lowe’s already has plans to deploy with FedEx, and FedEx says it is talking to Pizza Hut and Walmart about doing their deliveries as well.

Low-tech options

Some say low-tech is still the best route to low carbon. Many European cities have companies such as Deliveroo using bicycle couriers for fast, zero-emission meal deliveries from local restaurants. The system could be extended for other goods. Ford recently developed software that could summon bike couriers to take parcels in a suburban London neighborhood the last mile from truck to front door. 

Lockers in shopping malls also get around the last mile problem for online retailers. Customers are given a code and pick up their own package. But if you drive there, the carbon gain is lost.

Bicycle-based delivery now used for restaurant meals could easily be adapted to online purchases. Photo courtesy of TaylorHerring from Flickr, licensed under CC BY-NC-ND 2.0

The new kid on the block is crowd-shipping — hitchhiking for parcels. Start-ups like Roadie promise to “connect people who have stuff with driver already heading that way.” Drivers make bids to deliver. Right now in some places, half of all crowd-shipping trips are made specially for the delivery, while another third take long detours. So the potential carbon saving disappears. But the more people join in, the more efficient it could be.

The bottom line

The bottom line? Online shopping can be greener than driving to the store. Novel last-mile alternatives to conventional delivery trucks stand to make it even more environmentally friendly.

But the devil is in the details. If we bundle our orders, and avoid the speedy delivery option, we boost the environmentally friendly quotient. (Imagine if we were offered a “green shipping” button when choosing dispatch options?) Other tips for reducing delivery’s environmental impact: Do be in when the courier calls. Don’t buy on a whim and then take up the “free return” option.

Oh, and don’t binge on stuff. Some say the real danger from online shopping is it encourages us to buy stuff we wouldn’t otherwise. The purchase that doesn’t happen has the lowest delivery carbon footprint of all.