Craigslist and other such websites where people go to unload unwanted items may be encouraging behavior that benefits the environment, according to research from Penn State.

Using Craigslist and other online exchanges to post advertisements for items they want to get rid of may result in more people selling or giving away these unwanted items than simply having them end up in some landfill, according to Suvrat S. Dhanorkar, assistant professor of supply chain management at Penn State.

Looking at data concerning Craigslist, in particular, Dhanorkar determined that whenever the site entered a geographic market, a 2 to 6 percent drop in that market’s annual municipal solid waste occurred.

"Consumerism has grown exponentially — I don't want to take a side whether that's good or bad — but that's a fact and it's going to grow," said Dhanorkar. "As more and more countries become wealthier, the people there are going to consume more, but while consumerism is here to stay, the waste need not be. We may be able to let consumerism grow while, at the same time, we can also cut back on the surplus or waste that is being generated in the system by reusing more products."

As a result, Dhanorkar predicts that item exchange sites could eradicate millions of tons of landfill waste, potentially saving billions of dollars in waste management costs.

"In the case of New York City, the city spends about $2.3 billion annually on managing the 7.8 million tons of municipal solid waste, which is generated by 8.5 million people," said Dhanorkar. "According to the estimates, a 2 to 6 percent reduction in municipal solid waste, owing to Craigslist entry, would lead to approximate annual savings worth millions of dollars for large cities. That's millions of taxpayer dollars that could be diverted from managing waste to other needs."

Likewise, Dhanorkar believes that in large cities, the estimated 2 to 6 percent decrease in municipal solid waste brought about by sites like Craigslist could also spur a corresponding reduction (an estimated 200,000 to 600,000 tons) in greenhouse gases.

The study is published in the journal Management Science.