FORTUNE — Craton Equity Partners, a private equity firm focused on companies that “improve the environment and quality of life,” is back in the fundraising market.

The Beverly Hills, Calif.-based firm is seeking upwards of $400 million, according to a regulatory filing. This follows a 2006 debut fund that was capped just south of $200 million. Through the end of 2011, CalPERS reports that Craton’s first fund featured an internal rate of return (IRR) of negative 7.3%.

Existing portfolio companies include Arxx, a maker of insulating concrete forms; Enlink Geoenergy Services, an installer of earth heat exchangers; Liquid Environmental Services, a non-hazardous liquid waste collection and treatment company; and Gazelle, a “recommerce” company focused on used consumer electronics.

Fortune has left a message with Craton, and will update this post if we hear back. In general, private equity firms are prohibited from discussing fundraising efforts.

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