TripAdvisor’s GreenLeaders program has doubled its hotel participation, from 1,000 to more than 2,000 participating properties, since its launch in April.

The travel site says this makes GreenLeaders the largest national green hotel program that directly assesses eco-friendly practices.

Participating brands include Best Western, Carlson Rezidor Hotel Group, Fairmont Hotels & Resorts, Marriott International and Select Registry, as well as numerous independent hotels.

Additionally, the American Hotel & Lodging Association (AH&LA) has integrated TripAdvisor GreenLeaders’ minimum eco-friendly requirements as part of its Green Guidelines. Now accommodations meeting the AH&LA guidelines will also qualify for the TripAdvisor GreenLeaders program.

To meet TripAdvisor GreenLeaders’ minimum requirements, hotels must:

• Track energy use on a regular basis (at least quarterly).
• Use at least 75 percent energy-efficient light bulbs.
• Have a current and active towel re-use plan in place.
• Have a current and active linen re-use plan in place.
• Recycle at least two types of waste.
• Train staff on green practices.
• Educate guests on green practices.

The TripAdvisor GreenLeaders program considers a property’s holistic approach to sustainability and ranks them based on four levels of participation — bronze, silver, gold or platinum — which is displayed on the property’s listing on the TripAdvisor site. The more green practices a hotel has in place, the higher its TripAdvisor GreenLeaders level.

AH&LA first launched its sustainability guidelines in 2008, and has updated its existing 11 guidelines to 14 aligned with TripAdvisor GreenLeaders’ criteria, including two new guidelines from the program: how to train staff on implementing green practices and how to provide information to guests on the hotel’s green practices. The additional aligned criteria are towel and linen re-use programs, using energy-efficient light bulbs, tracking energy usage, and recycling.

TripAdvisor GreenLeaders was developed in partnership with the EPA’s Energy Star program, the US Green Building Council, and the United Nations Environment Programme. Since the program’s launch, more than 100,000 travelers have searched for green hotels on TripAdvisor, the travel site says.

One of TripAdvisor’s GreenLeaders — Marriott — decreased landfill waste per occupied room in its Americas region by 4.9 percent from 2011 to 2012, the company announced in its 2013 sustainability report update.