The U.S. Securities and Exchange Commission has charged two companies and their executives for running a $30 million ponzi scheme to defraud mostly elderly investors, who thought they were putting money into eco-friendly projects.

The SEC filed the complaint against Wayde and Donna McKelvy of Denver-based Speed the Wealth and Troy Wragg and Amanda Knorr of Mantria Corp. in Pennsylvania.

The four defendants reportedly used seminars and webinars to convince more than 300 investors, particularly those who have retired or are near retirement, to buy bogus shares of Mantra. The investors were led to believe that their money went to projects such as a "carbon negative" residential community in Tennessee and the development of a charcoal substitute from organic waste (biochar), the SEC said.

Mantria had claimed to be a major global producer of biochar with many factories. But the company never sold any biochar and had one facility testing biochar for eventual commercial sales, the SEC said. And there was no plan to build an eco-friendly community in Tennessee – Mantria did re-sell vacant lots that were supposed to be used for such a project.

Some of these investors took money out of their retirement plans or home equity to invest with Mantria. The four defendants allegedly told investors that they could enjoy 17 percent to "hundreds of percent" of returns on their investments annually.

The two companies used the money from the investors to pay other investors for their returns. The McKelvys also reportedly received a 12.5 percent commission for their work, the SEC said.