More than 300 investors nationwide were lured into a $30 million Ponzi scheme that focused on "green" investments, according to the Securities and Exchange Commission.

The SEC on Monday charged four people and two companies in the scheme, which it says targeted elderly investors or those nearing retirement to finance projects of Pennsylvania-based Mantria Corp. The projects included a supposed "carbon negative" housing community in rural Tennessee and a "biochar" charcoal substitute made from organic waste.

The SEC's complaint, filed in federal court in Denver, charges Mantria Corp. and Speed of Wealth LLC as well as Wayde and Donna McKelvy, who were previously married and living in the Denver area, and Mantria executives Troy Wragg and Amanda Knorr, and seeks an emergency court order to freeze their assets.

The McKelvys promoted Mantria investments through their Denver-based company Speed of Wealth and particularly targeted elderly investors or those approaching retirement age to finance Mantria's "green" initiatives, the SEC charges. With the help of Wragg and Knorr, they convinced investors attending seminars or participating in Internet Webinars to liquidate their traditional investments such as retirement plans and home equity to instead invest in Mantria, the SEC says.

The SEC alleges that the "green" representations were laced with bogus claims, and investors were falsely promised enormous returns on their investments ranging from 17% to "hundreds of percent" annually. In fact, Mantria's environmental initiatives have not generated any significant cash, and any returns paid to investors have been funded almost exclusively from other investors' contributions, the SEC says.

The complaint alleges the defendants overstated the scope and success of Mantria's operations in several ways to solicit investors. For instance, they claimed that Mantria was the world's leading manufacturer and distributor of biochar and had multiple facilities producing it at a rate of 25 tons per day. In fact, Mantria has never sold any biochar and has just one facility engaged in testing biochar for possible future commercial production. Furthermore, Mantria's only source of revenue has been from its resale of vacant lots for its purported residential communities in rural Tennessee, but those did not generate cash with which to pay investor returns because Mantria provided 100% financing for almost all of its vacant lot sales to buyers using other investors' funds.

The SEC alleges that Mantria and Speed of Wealth used investor funds to pay returns to other investors in typical Ponzi scheme fashion. Mantria and Speed of Wealth also did not tell investors that they kept a significant amount of their funds to pay commissions of 12.5% to the McKelvys.

The SEC's complaint charges each of the defendants with violating the antifraud and offering-registration provisions of securities laws. The SEC also charged all of the defendants except for Mantria with violating broker-dealer registration requirements. The SEC seeks injunctions, disgorgement, and financial penalties from the defendants.