E-shopping is greener

A new study by Carnegie Mellon’s Green Design Institute can make students feel better about how their online purchases affect greenhouse gas emissions.

The study was led by H. Scott Matthews, associate professor of civil and environmental engineering and director of the Green Design Institute, and it compared the energy consumption and carbon dioxide emissions associated with customers purchasing a flash drive from a traditional retailer to purchasing the same item from

A traditional retailer’s supply chain typically operates by shipping goods from manufacturers to distributors who then ship to regional warehouses to store the goods, finally shipping them to actual retail stores.’s Internet retail model eliminates these intermittent steps and associated carbon dioxide emissions by shipping directly from distributors to customers through a parcel service.

“In a study of this nature with numerous variables, we took great care to estimate average- case performance using simulations and approximations,” Matthews said. “We were able to show that in the majority of cases studied, the e-commerce model does perform better than shopping at traditional retail in the areas of carbon dioxide emissions and energy consumption.”

According to the study, ground shipping in’s model uses 35 percent less energy and carbon dioxide emissions than a traditional retail model; when express air shipping is used, the difference is smaller, but still in favor of the e-commerce model.

Emissions from such factors as individual packaging and delivery, as well as computer and data center use, apply only to the commerce model.

The most significant element, however, only applies to the traditional method of purchasing: 65 percent of the emissions associated with the traditional model result from customer transportation to and from the retail store.

“These results are surprising to me; I never would have guessed that customer transportation is such a huge factor,” said junior decision science major Andrea Tan.

Many Carnegie Mellon students make purchases online of everything from books to clothes to electronics.

“I’ve been buying online a lot more since I came to college,” said Natalie French, a first-year civil and environmental engineering major and eco-rep. “It’s easier for me to buy something online than to take time to go to the store.”

“For me it’s all about the time,” remarked Anna Lenhart, a junior civil and environmental engineering major and vice president of Carnegie Mellon’s Engineers Without Borders chapter. “If I need something right away then I will buy it in a store, but if I can wait for shipping, I will definitely purchase online.”

While students interviewed said they wouldn’t likely change their purchasing habits in light of these results, French added that she likes buying online even more now because “it gives me more hours in a day and saves the world.”

Some students like the idea of going green while saving money. “I buy online because it’s cheaper; reducing carbon emissions is icing on the cake,” said Eddie Yuen, a junior civil and environmental engineering major and eco-rep.

The study, “Life Cycle Comparison of Traditional Retail and E-Commerce Logistics for Electronic Products: A Case Study of,” can be found at