David Gelbaum

Gelbaum is done with philanthropy. He’s already given away most of his fortune and lost much of the rest. Not long after he retired from TGS, a Los Angeles Times report identified him as the anonymous donor who’d been bankrolling the Sierra Club and helped a conservation group buy a large chunk of the Mojave Desert. He acknowledged the gifts and has since disclosed more than $1 billion in giving, including support for Iraq and Afghanistan war veterans and the American Civil Liberties Union. In a handful of interviews, he’s avoided saying much about the source of his wealth. After leaving TGS, Gelbaum bet heavily on green technology: biofuels, solar panels, smart grids. The New York Times reported in 2010 that he’d invested $500 million of his fortune in green companies and given away or paid in taxes most of the rest. He took a role that year as chief executive officer of Entech Solar (ENSL), a Texas company he’d been supporting financially. In 2012, the company announced that it was running out of cash and that Gelbaum had stopped propping it up. Other companies in his portfolio faced challenges. The next year, he and his wife announced they were “not in a position to give more” to charity. Nor did they expect they’d ever be.