CNN — In Nelson Mandela Bay, in the Eastern Cape of South Africa, thousands of hectares of land could one day become the world’s largest green ammonia plant. Ammonia, which is made up of nitrogen and hydrogen, is commonly used as a fertilizer. In the early 1910s scientists devised a way to synthesize it, but before then, the main agricultural fertilizer was guano, bat or bird excrement, which had to be obtained from tropical islands and was in short supply.