Walmart and other large companies are pushing their suppliers to reduce packaging, waste and energy use to save companies money and reduce carbon pollution. The goals of zero waste and 100 percent renewable energy are big and audacious. According to Aron Cramer, CEO of Business for Social Responsibility such goals are also necessary. "We won't be able to maintain economic growth if the environment starts to get in the way," he says.  Along with important steps towards a more sustainable supply chain Walmart has an emphasis on energy. "Energy efficiency has to go hand in hand with renewable energy," says Andrea Thomas, Senior Vice President of Sustainability at Walmart. To Walmart renewable energy is a business opportunity and she says they now in a position to start scaling. Aron Cramer agreed with the significance of renewables saying distributed energy could "be a business opportunity for retailers."  A conversation with two top executives on sustainable capitalism.