Kate Harrison, author of "The Green Bride Guide," talks to NBC about the benefits of having a green wedding (see video below). Harrison said that with 2.2 million weddings annually in the U.S., "everyone doing one little thing 2.2 million times, it really adds up." She said that going green is cost effective. Couples can save as much as 40 percent by making "really simple green choices." At her wedding, Harrison replaced new centerpieces with silver pitchers from family and friends filled with local flowers. One of the challenges of an eco-friendly wedding is making sure "to get your vendors on board," said Harrison, who will soon be launching a green wedding gift registry on her blog thegreenbrideguide.com.