DENVER -- Wooden key cards will be given to guests at 35 Denver-area hotels during the DNC as part of the convention's green push.

Boulder-based Sustainable Cards has spent years developing a way to create the cards and is donating them to the delegate hotels in hopes of getting bigger contracts with those chains later on.

Sustainable Cards CEO Greg Hartmann said 240 million plastic key cards are discarded every year, which he said is the same as burying seven 777 airplanes in a landfill.

Hartmann said he knows many of his cards will also end up in the landfill, but said because they're made of wood, they'll biodegrade. They're also a sustainable resource, because new trees can be planted to replace those used to make the cards.

Hartmann also said that because they're simply wood shavings, and not processed plastic, even the process of creating them is better for the environment.