West Lafayette, Indiana - Shoppers sitting down at their computer to take advantage of online sales are helping the environment, said a Purdue University professor.

Online shopping has grown consistently over years, with online sales accounting for 9 percent or more of all holiday spending.

Gregory Shaver, a professor of mechanical engineering, said the resulting home deliveries push the possibilities of online shopping benefiting the environment.

"If you are no longer driving from your house to the mall, then the goods you are buying online often are being delivered," he said. "That shifts the freight transportation from your vehicle to larger freight trucks. They're often powered by diesel and are inherently more efficient."

Shaver said the significant growth of e-commerce during the past 15 years has resulted in more of the larger delivery trucks on the road.

"Larger vehicles are operated by fleet operators who pay attention to their bottom line," he said. "And these vehicles are built specifically to efficiently move goods. That translates to less fuel use. With less fuel usage, there are less carbon dioxide emissions and less greenhouse gases."

Shaver noted that recognized environmental benefits, and increased use of freight trucks, increase the need for investments to further improve those larger delivery vehicles.