Close icon Two crossed lines that form an 'X'. It indicates a way to close an interaction, or dismiss a notification. Win McNamee/Getty Images This story is available exclusively to Insider subscribers. Become an Insider and start reading now. Elon Musk's XPRIZE revealed on Monday new details of a $100 million contest for technologies that capture and store carbon dioxide. The contest will run for four years and officially launch on Earth Day, April 22. We talked to top VCs including Vinod Khosla in December about which startups to watch, and they offered four that are working on carbon capture tech.