It seemed like a terrific business opportunity. Consumers and businesses were eager to buy eco-friendly products. So in 1991, Wausau Paper Corp. launched its EcoSoft line of paper towels and tissues, made from 100 percent recycled content. It wasn’t exactly a success story. The problem: Wausau’s green marketing was lost amidst a welter of other companies’ eco-friendly claims. The number and variety of claims confused potential customers, who weren’t sure which products were truly green. So purchasers often stopped responding to green marketing. Wausau didn’t give up. In late 2003, it got Green Seal to certify its EcoSoft products as environmentally friendly. Green Seal, an independent nonprofit, tests a wide variety of products and services and inspects manufacturing plants to determine whether a product or service meets Green Seal’s environmental standards. If it does, the product or service can display the Green Seal certification mark. Once Wausau put the Green Seal certification mark on its EcoSoft products, sales soared. In 2004, the market for paper towels and tissues grew 2 percent, but EcoSoft sales rose 16 percent. In 2005, sales jumped an additional 25 percent, and in 2006 sales shot up 26 percent. Thanks to the Green Seal mark, Wausau was able to demonstrate that certain products in its line were truly green, which brought in a lot of new customers. This is part of a rapidly growing trend. More companies around the U.S.,including Westinghouse Electric, Sony, Dell, 3M, GE and Toyotaare using certification marks to prove their green credentials and boost sales. They also are finding the certification process often brings other benefits: It pushes businesses to improve their plants and business processes in ways that significantly reduce their costs. But businesses need to be cautious when using green certification marks. The number of these marks is growing rapidly, and companies should carefully consider the costs and benefits before seeking certification.