If you’ve been hankering for a resource that culls the best of eco-friendly travel suppliers, look no further.

Sustainable Travel International (STI) launched its Green.travel site today, which boasts a list of about 4,500 travel suppliers that employ some level of sustainable practices, covering tour operators, cruise lines, hotels and resorts, and more.

Because there are varying degrees to just how green a company is, Green.travel also unveiled a new five-tier rating system—the Green Suitcase—which helps consumers determine the level of commitment a company has to being truly sustainable. The system is based on the progress the companies have made in incorporating sustainable travel principles into their business practices. The more vested a supplier is in being green, the more suitcases they will be awarded.

Green.travel has been in the works for years, according to White Salmon, Wash.–based STI, a non-profit organization dedicated to providing education and outreach services in the travel industry to support environmental conservation and to protect cultural heritage while promoting cross-cultural understanding and economic development.

“The initial companies listed include STI partners, lodges and tour operators certified or rated by a third party—for example Fair Trade Tourism South Africa, our marketing to our network, and community-based tourism entities,” said CEO Randy Durband.

“The criteria and ratings are determined very carefully by STI experts who work directly with GSTC, the global body for travel certification,” added Durband.

Global Sustainable Tourism Criteria (GSTC) was established at the World Conservation Congress in 2008 and is a set of 37 voluntary standards that “help protect and sustain the world’s natural and cultural resources while ensuring tourism meets its potential as a tool for poverty alleviation.”

There is no charge to be included or promoted on Green.travel, should a company meet the criteria for listing, nor any commission fees or similar monetary incentives involved in any of the online recommendations, bookings or transactions, said spokesperson Alexia Nestora.

“In the coming months, we’re hoping that large to small travel companies that support the principles of sustainable travel will immediately recognize the benefits to them and their ideals by becoming part of Green.travel,” Nestora said. “Our vision, as we state on our home page, is ‘that through working together, trip by trip, we can protect the environment, preserve authentic cultural heritage and promote the social and economic well-being of local communities.’”

In addition to listing and ranking green companies in order to help people learn about sustainable travel practices, the site’s online booking program will automatically take 1 percent of a client’s reservation costs and donate it to credible, well-managed sustainable travel initiatives.

For more information, visit Green.travel.