The U.S. Postal Service may be in the red but they’ve been promoting going green this holiday season.

“The Postal Service is one of the greenest mailing and shipping companies in the world,” said Thomas G. Day, chief sustainability officer. The eco-friendly options offered by USPS include mailing and shipping supplies, free package pickup and holiday cards printed on recycled paper available in 2,000 Post Offices.

“We have a ‘fleet of feet’ delivering mail the greenest way possible, by walking,” Day added. “Nearly 9,000 of our carriers will be delivering holiday mail on foot this season. And we also have nearly 80,000 ‘park and loop’ routes, where carriers will drive vehicles from the Post Office to neighborhoods and then deliver those holiday packages and cards on foot.”

The Postal Service will have delivered a total of 16.5 billion cards, letters and packages between Thanksgiving and Christmas Eve using various alternative fuel vehicles in the largest civilian fleet in the world of 215,000 vehicles. Alternatives utilized by USPS include three-wheeled electric vehicles with zero gas emissions that operate at a cost of only 2 cents a mile, as well as vehicles that can operate on compressed natural gas, propane, ethanol, and fuel cell. There’s also 30 large all-electric trucks delivering holiday mail in Manhattan.