In October 1908, Fritz Haber filed a patent on the “synthesis of ammonia from its elements.”
This achievement led to his 1918 Nobel Prize in chemistry. He collaborated with an industrial colleague, Carl Bosch, to develop the Haber-Bosch process to manufacture large quantities of nitrogen fertilizer as well as explosives. And thus humans faced another “swords and ploughshares” choice.
The implications of Haber’s relentless tinkering in a lab in Germany 100 years ago have been profound.
Since the First World War, producers have applied the energy-intensive Haber-Bosch process with zeal. In the last century, the curve on a graph showing the exponential growth of nitrogen fertilizer use overlaps closely with a curve showing energy use in agriculture and also with another curve indicating the growth of the human population.
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What will the impact be as energy supplies become limited?
The Haber-Bosch process achieves a temperature of 450 C and a pressure of 200 atmospheres to manufacture nitrogen fertilizer. Nitrogen gas molecules, in the form of two nitrogen atoms locked together with triple bonds, make up 78 percent of our air.
Contained heat and pressure split these nitrogen atoms apart and tack on a hydrogen atom to each broken bond of nitrogen atoms to form NH3, or ammonia. For this transformation, we need fossil fuel energy and also natural gas as a source of hydrogen.
In contrast, rhizobia, lowly bacteria on legume plants such as peas, beans and clovers, use enzymes and little energy in the form of carbohydrates from their host plants to do the same job.
Legume plants receive nitrogen from rhizobia, and rhizobia receive carbohydrates from legume plants. This ancient trade deal is ours to exploit and our example of civility.
In 1798, the dour Reverend Thomas Malthus warned that if our human population increased exponentially, food production would still only increase linearly, and the human race could not escape from this law.
A century or so later, Haber appeared to give us the key for our escape. With the generous lubrication of energy, this key worked well. Human population, nitrogen fertilizer use, food production and energy use all increased exponentially.
Today, as energy supplies dwindle and as greenhouse gas emissions increase from the burning of fossil fuels, excess domestic livestock production and excess nitrogen fertilizer, we might do well to heed Malthus’s warning.
It was only a warning, after all, and not a challenge to act as if biological limits do not apply to modern, scientific people. Science based on ecological realism will serve us more effectively than science based on human hubris and fantasies.
Organic farms in Europe and China yield considerably less than conventional farms, but that’s because conventional farms use relatively high nitrogen fertilizer applications per acre. In North America, organic farms produce 90 to 95 percent of the yields of conventional farms and in some African countries, organic farm yields exceed those on conventional farms.
On a global scale, low proportions of farms are organic.
Will we be able to feed the world without manufactured nitrogen?
Many agronomists argue that we cannot, but they tend to assume that we must continue to produce not only similar amounts of food but annually increase amounts to backstop growth.
Others suggest that relying on legume nitrogen while reducing meat consumption, especially from grain-fed animals in feedlots, might address potential food shortages.
Other approaches are to recycle rather than waste nutrients, including human sewage, and to rely more on urban gardens, farming all productive land near cities and adopting organic methods.
What will a retreat from using manufactured nitrogen mean?
Vaclav Smil at the University of Manitoba argues that 40 percent of humans depended on nitrogen fertilizer in 2000. A more recent estimate, published in Nature in October 2008, is that 48 percent, almost half of humanity, depend on nitrogen fertilizer for their food supply.
One-third of the energy consumed in agriculture is used to make nitrogen fertilizer. Even if human populations do not grow, we are also using nitrogen fertilizer to grow biofuel and biomass crops. Thus the demand for nitrogen fertilizer is expected to go beyond the savings from improved efficiencies.
One hundred years ago, the miracle of nitrogen fertilizer helped us crash through restraining boundaries and more became possible. Many people owe their lives to it under the prevalent production methods of today, while fossil fuels decline and greenhouse gases emissions increase.
Ralph C. Martin, PhD., P.Ag. is the founding director of the Organic Agriculture Centre of Canada. Please send comments or questions to 902-893-7256 or e-mail oacc@nsac.ca.
