David Keith is a bit fidgety. Maybe that's because venture capitalists have asked to come see his carbon dioxide machine. Maybe it's because the project is running months behind schedule, as experiments so often do. Maybe it's because his critics say it'll never work.
Or maybe it's a taste of excitement, because it seems entirely possible that the trailer-truck-size machine that he's leaning up against is actually going to work.
"It's amazing to see all this talk and paper get turned into hardware," he says. "I really love it."