Phrase of the Week: Haber-Bosch Process

November 18, 2011

Referred to by some as the most important technological advance of the 20th century, the Haber-Bosch process fixes nitrogen from the air with hydrogen from natural gas to produce ammonia, a critical component of modern fertilizers. It was the first industrial process to use high pressure to promote a chemical reaction.

Developed shortly before World War I by Fritz Haber, and perfected as an industrial process by Carl Bosch, the process is viewed as a critical component of Earth’s population explosion over the past century. Between 3 and 5 percent of the world’s annual natural gas production – roughly 1 to 2 percent of the world’s annual energy supply – is converted using the process to produce more than 500 million tons of nitrogen fertilizer, which is believed to sustain about 40 percent of the world’s 7 billion people. Approximately half of the protein in today’s humans originated with nitrogen fixed through the Haber-Bosch process.

Because nitrogen molecules are held together by powerful triple bonds, the Haber-Bosch process must use a catalyst of iron or ruthenium within an environment of intense heat (over 800 degrees Fahrenheit) and pressure (roughly 200 atmospheres) to bring together the nitrogen and hydrogen. Each time the gasses move through an industrial reactor, only about 15 percent of the elements convert to ammonia, but by recycling the unfixed nitrogen and hydrogen, overall industrial conversion generally amounts to about 98 percent.

Ironically, while half of today’s global population exists because of the Haber-Bosch process, many hundreds of thousands died during World War I when BASF’s first industrial ammonia production plant was converted from making fertilizers to making explosives.

Scientists working at SLAC’s Stanford Synchrotron Radiation Lightsource have taken an important step toward understanding how microbes in the soil fix nitrogen without high pressures or temperatures. They identified a key atom at the heart of an enzyme called nitrogenase which plays a critical role in converting nitrogen in the air into a form that living things can use.

Researchers hope they can eventually reverse-engineer this enzyme to come up with a more efficient and environmentally friendly alternative to the Haber-Bosch process.