One hundred years ago this month, ground was broken in Oppau, Germany, for a plant that would help transform the world-and the Chesapeake Bay. It marked the first industrial-scale attempt to synthesize nitrogen from the atmosphere into a reactive form that could be used for fertilizer, as well as munitions, using a process developed three years earlier by German scientist Fritz Haber.

Although scientists knew that nitrogen made up the bulk of the air we breathe-it's 78 percent of the atmosphere-they had long been stymied about how to convert that into forms humans could use.

Farmers and scientists recognized that food production required adequate nitrogen, and by the late 1800s, nitrogen from massive guano piles from bird droppings in Chile were actively being mined and exported to meet a growing demand, but those supplies were limited.

William Crookes, a British chemist, warned in a famous 1898 speech that "all civilized nations stand in peril of not having enough to eat" and that finding a way to "fix" nitrogen from the atmosphere was the great challenge for world chemists.

Haber was able to convert N2 from the atmosphere using a process involving high pressures and large amounts of energy. The result was 4 ounces of ammonium an hour. The German company BASF purchased the rights to the process, and its scientist, Carl Bosch, got the job of scaling up the process and making it more economical. In 1914, its first full year of operation, the Oppau plant was producing 20 tons of ammonia daily.

Today, more than 100 million metric tons of nitrogen fertilizer produced through the Haber-Bosch process are applied to fields globally, providing three times the amount of agricultural nitrogen than the next largest source: the planting of legume crops such as soybeans and alfalfa which, unlike most other plants, can meet nitrogen needs by fixing it directly from the atmosphere by virtue of bacteria associated with nodules in their roots. (In the United States, the ratio is a bit closer, with about 11 million metric tons coming from the Haber-Bosch process, and a bit less than 8 million from legumes.)

It is hard to overstate the significance of the Haber-Bosch process. In his 2001 book "Enriching the Earth," Vaclav Smil, a distinguished professor of geography at the University of Manitoba, Canada, calls it "the single most important change affecting the world's population-its expansion from 1.6 billion people in 1900 to today's 6 billion-would not have been possible without the ability to synthesize ammonia."

Smil estimated that about 40 percent of the global population owed their very existence to the Haber-Bosch process, without which they would starve.

But the process has been a mixed blessing for humanity, Smil noted. It has provided food for many people, but also led to diet changes-including the consumption of more proteins and increases in corn-derived sugar use-that contribute to increased obesity and food waste.

The ready availability of fertilizer also caused a huge amount of nitrogen to be released into the environment, leading to eutrophication in coastal waters such as the Chesapeake Bay and other problems. Globally, the problem is expected to worsen as more people become more affluent and demand a more protein-rich diet.

"The desire to consume more animal foods is virtually universal but, powerful as it may be, the North American dietary pattern is not only an inappropriate attractor, it is utterly unrealistic," Smil wrote in a 2002 paper calling for altered diets, improved agricultural efficiencies and reduced food waste to moderate "the worrisome human interference in nitrogen's biospheric cycle."

The Haber-Bosch process also has a dark side. Various forms of nitrogen are also critical to manufacture munitions. During World War I, production at the Oppau plant was redirected to support the war effort-an action widely credited for prolonging the fight. The last year of the war, 1918, was also the deadliest.

By World War II, plants around the globe world using the Haber-Bosch process helped to produce munitions for an even deadlier conflict.

The Oppau plant wasn't one of them, though, On Sept. 21, 1921 a silo storing 4,500 tons of a mixture of ammonium sulfate and ammonium nitrate fertilizer exploded, killing 500 -600 people and injuring 2,000 more. The blast was so powerful it was heard 300 miles away in Berlin.