Online textbook rental company Chegg is working with the company Eco-Libris on its commitment to plant one tree for each textbook rented on its Web site.

The goal of Eco-Libris is to promote “sustainable reading,” and to achieve that end the company offers visitors to the site the ability to “balance out” their books by buying one tree per book at a cost of one dollar a tree.

The Web site offers a wide variety of college textbooks available for rental rather than for purchase, meaning costs are lower and books are reused. Since the tree planting depends on each rental transaction, one book can generate a significant increase in vegetation.

“Every time a book is rented a tree is planted, so you get a lot of bang out of one book,” said Maria Reiling, Chegg’s vice president of marketing.

There are a variety of online textbook rental companies with eco-friendly or humanitarian agendas, but Chegg is the only one with a tree-planting program.

However, Eco-Libris is the company that actually organizes planting, via nonprofit organizations in the United States and the United Kingdom that work in Nicaragua, Belize, Guatemala, Honduras, Panama and Malawi.

Chegg decided to start working with Eco-Libris this past fall after becoming aware of research indicating more than four million trees a year are used to make textbooks in the United States alone. To counter the resultant deforestation, Chegg formed a partnership with Eco-Libris last autumn and has funded the planting of more than 100 acres (equal to 25 city blocks) to date, Reiling said.

Tree planting is important for some students, but others focus on the bottom line when choosing a textbook vendor.

Junior Krista Seabrook found out about Chegg from her mother, who read an article in Newsweek that featured several online textbook rental companies.

“I like that they do [plant trees], but it was not a motivating factor,” she said. “The reason I chose them is because they let you highlight [the books.]”

Seabrook has been using the Web site since the beginning of the school year, and estimates that she has saved about $50 a quarter on books for her international studies classes.

Chegg recently added Plant a Tree USA as a partner, and continues to look for other organizations with the same business and environmental values.

“The founders [of Chegg] have focused on saving money and helping the environment, right from the start,” Reiling said. “We are always trying to find new ways to expand on that.”