Third Derivative (D3) is a climate tech accelerator programme, not a venture fund. Its own About page states it was "Founded by RMI and New Energy Nexus" and that it "launched in December 2020 with 46 companies"; RMI's own launch announcement of 4 June 2020 described it as "a new joint venture called Third Derivative (or D3, for short)". RMI's current boilerplate describes it simply as "RMI's global climate tech accelerator". The programme runs a flexible, remote, roughly 18-month accelerator with two general cohorts a year plus focused programmes (Industrial Innovation cohorts for steel, cement and chemicals; First Gigaton Captured for carbon dioxide removal; the Clean Mobile Power Initiative; and cooling), and states it connects startups to corporate partners, investor partners and RMI's technical network rather than acting as the primary source of capital itself. RMI's 2020 launch announcement described an optional $100,000 seed investment made with investor partners providing the capital. An affiliated investment vehicle does exist: RMI's staff bio for Pilar Carvajo Lucena states that she oversees "the investments of the D3 Accelerator Funds", and D3's Head of Operations bio lists "investment fund operations" among his responsibilities. No size, vintage or assets-under-management figure is published for those funds. D3 says its portfolio numbered 286 climate tech startups from 27 countries as of August 2025 and states that those companies have raised over $3.7 billion since joining; that is capital raised by portfolio companies, not capital managed by D3.