Being environmentally conscious is seen as being good for business, but it's important to prove it's not just talk.

CHICAGO (MainStreet) -- When the first Earth Day was held in 1970, it was a grassroots, people-powered movement, with events organized by environmental activists and conservation-minded students. Corporate America was kept on the sidelines.

Fast-forward 40 years, and U.S. companies are eager to align themselves with the Earth Day spirit. Major international corporations from GE(:GE) to Cargill to Coca-Cola(:KO) brag about their sustainability initiatives on their websites, while the world's largest retailer, Wal-Mart(:WMT), has made energy conservation a central message of its corporate marketing. Being environmentally conscious is seen as being good for business, but it's important to prove it's not just talk.

Unlike 1970, many of the Earth Day events we saw Sunday were paid for through corporate sponsorship. Which means going green is seen as being good for business.

But how do you know if a company really walks the walk? It's one thing to say you care about the environment; it's another thing to completely revamp your supply chain to eliminate waste. Small businesses that have invested a lot of time and money into improving sustainability want customers and suppliers to know that their concern for the environment is more than just good PR.

That's why it's become increasingly important for small businesses who take sustainability seriously to get a stamp of approval from an independent third party. It shows customers that the company doesn't just boast of being green, but can back up that boast with specifics.

Certain industries have their own specific certification processes. Organic food, for example, is regulated by the USDA's National Organic Program, while builders and architects can get LEED certification for their projects through the U.S. Green Building Council. Business whose products are not covered through an industry-specific agency can apply to an independent organization that offers green credentials.

The certification group with the longest track record is Green America, a nonprofit organization with impeccable environmental credentials that was founded in 1982. The group assesses businesses based on their environmental practices and social justice initiatives, meaning workers' rights and community involvement are just as important as recycling and conservation.

A small business can get the Green America "Seal of Approval" if it actively promotes positive social change or uses environmentally responsible sourcing, manufacturing and marketing. Companies can also earn the designation of "Green Certified Business" at three different levels (the highest, Gold, is reserved for companies that show leadership within their industry and make social responsibility a core of their mission). The organization works on a membership model, with members given access to assessment tools and educational materials. The organization also encourages peer-to-peer networking through meetings and webinars.

Two other organizations, founded more recently, also offer green certification, with a focus on environmental practices rather than the broader, social justice mission of Green America. The Institute for Green Business Certification assesses all aspects of a company's environmental impact, including waste removal, energy efficiency, water use and carbon footprint. The organization works on a consultant model: A small business is assigned an environmental analyst who works one on one with the company through telephone calls and on-site visits.

Another resource is the Green Business Bureau, which emphasizes the marketing opportunities green credentialing can provide. Companies start by taking an online assessment, then get individualized action plans, suggestions for specific activities and links to online vendors that supply green-friendly products. Members also get a "Marketing Tool Kit" with sample press releases, website keyword suggestions and other strategies for drawing attention to their green credentials.

Now that Earth Day has gone mainstream, it's in every company's interest to show concern for the environment. But consumers have gotten sophisticated, and businesses that that don't back up their environmental claims with concrete actions are quickly accused of "greenwashing" -- a guaranteed way to lose credibility.

Businesses that display a green certification in their office window or on the home page of their website want the public to know that sustainability is a year-round priority. And going through the process of certification might just inspire business owners to make other, even more impactful changes in their day-to-day routines.