Click for Climate Change: Study Finds Online Purchases 'Greener'

Online shopping is better for the environment than traditional brick-and-mortar retailing — 15 times better when it comes to carbon emissions, according a new study.

The study by market research firm GigaOm Pro and sustainability consulting group MindClick GSM took two identical $100 purchases, one done online and the other at a store, and compared them head-to-head.

Report author Dave Norem used Carnegie Mellon’s Economic Input-Output Life Cycle Assessment (EIO-LCA) model and publicly available emissions data to compare the carbon footprints of the two purchasing methods.

The model for online purchases included shipping, but excluded the emissions associated with the purchaser’s personal computer, which was estimated at 0.067 kWh and deemed negligible.

The in-store purchase model assumes the shopper makes a 20-mile round-trip drive to the store and back home again.

It’s a simplified model with room for adjustments here and there, but it’s hard to imagine that anything would drastically decrease the distance between the emissions associated with each type of purchase.

According to Norem, the model and resulting comparisons work best when applied to large and well-established retail companies with existing e-commerce sites and support, Target or Kohl's, for example. But the model still works when comparing a large online-only retailer, like Amazon, with a company that has both Internet and brick-and-mortar sales.

The drive to the store is part of the cost, but the store itself adds significantly to the total, the study found. Scaled to a $100 purchase, the building for one purchase produced 25.5 kg of CO2-equivalent, largely through the heavy carbon footprint involved in powering all those lights and keeping the temperature steady.

The study adds in 14 kg CO2-equivalent for the drive to and from the store to purchase that single item, compared to 2.57 kg of CO2-equivalent for the same package's movement as part of a larger shipment.

While it might seem like the large warehouses needed to fulfill online orders would bump up the emissions associated with online shopping, Norem points out that both shopping modes need these warehouses.

“Retail Distribution Centers consolidate incoming vendor shipments, and create outgoing shipments that are specific to a particular store, region or customer,” he explains. “With a small difference in the type of outgoing shipments, both the online or in-store purchasing scenarios are assumed to be identical to a warehouse as managed for online shipments. Put another way, Amazon's distribution center is very similar in size and scope as one for Target.”

While his report focused on Black Friday versus Cyber Monday, Norem says the results apply to online versus brick-and-mortar retailing in general.

Carnegie Mellon’s Green Design Institute found came to a similar conclusion earlier this year in a study showing how Buy.com’s e-commerce practices resulted in 35 percent less energy consumption and carbon dioxide emissions than what is produced in the traditional retail-shopping model.

In the recent months, online retailers have taken to using their lower emissions as a promotional tool to win more customers. Buy.com heavily promoted the results of the Carnegie Mellon study. Spud!, an online grocer serving the west coasts of the United States and Canada, frequently touts the statistic that its service helps avoid 120 car trips and that its local purchasing policies eliminate 1,000 food miles on average.