With environmental corporate marketing heating up, big agencies are beginning to flex their green muscles.

Today, MWW Group, one of the nation’s top public relations firms, launched a campaign – Take Charge, Initiate Change, Get Green – to reduce waste, conserve energy and become a more environmentally conscious organization.

To start, the firm has partnered with Carbonfund.org to offset its carbon emissions. Among the firm’s new policies, MWW Group will require that all offices recycle aluminum cans, plastic and glass bottles, and where possible, the agency will continue to recycle the hundreds of pounds of newspaper received by its offices. The firm is also changing all bulbs in its offices to energy star fluorescents.

If more top agencies position themselves as green, it could mean trouble for small firms that specialize in green marketing – at least when differentiating themselves to big companies.

A visceral understanding of environmental issues may be the biggest selling point the smaller agencies, like RenewComm, which launched last week, and Dwell Creative, which has been working in the green field since 2000, have.