“In 1909 Carl Bosch perfected a process invented by Fritz Haber which used methane and steam to pull nitrogen out of the air and turn it into fertilizer on an industrial scale, replacing the massive quantities of bird poop that had previously been needed to return nitrogen to depleted soils. Those two chemists top the list of the 20th-century scientists who saved the greatest number of lives in history, with 2.7 billion.18”