Nitrogen Fixation and Life

There are many chemical wonders in our world, but few are as important and complex as the chemistry of nitrogen. Nitrogen makes up 78% of our atmosphere. It combines with oxygen to form nitrates and with hydrogen to produce ammonia, both of which are essential for growing our food. Nitrogen fixation, which is how nitrogen gets from what we breathe to what we eat, is an amazing demonstration of design.

First, let us review a little high school chemistry. The atoms of all elements have electrons which give them their properties for forming compounds. The electrons are arranged in pairs with their magnetic poles designed so that in a stable arrangement, one electron’s north pole is matched with its neighboring electron’s south pole. The electrons have various orbitals with different energy levels. The atom is stable and chemically inert if an orbital is filled with all the paired electrons it can hold. For example, neon has 10 electrons. The first two orbitals each have two paired electrons, and the last orbital has six electrons in three pairs. This pairing of electrons makes neon an inert gas which does not combine chemically with other elements.

Nitrogen has an uneven number of seven electrons. So how does nitrogen become chemically stable? The answer is that two nitrogen atoms share three electrons, giving them stability. The two nitrogen atoms bond together to form a diatomic molecule that cannot be easily pulled apart to bond with other elements. How strong is the bonding? To break up a nitrogen molecule into two nitrogen atoms requires temperatures of 400 to 500 degrees Celsius and pressures of 200 atmospheres. So with nitrogen as the dominant element in our atmosphere, the atmospheric gases are stable and inert. Also, nitrogen is not a greenhouse gas that could threaten our temperatures on Earth. How then has God built a system that takes these stable nitrogen molecules and breaks their triple bonds to produce nitrates and ammonia?

If you think this isn’t an important subject, ask yourself where your food comes from? The answer is that 50% of the American diet is produced using artificial fertilizers containing nitrogen, which has been “fixed.” Nitrogen fixation combines that inert gas with oxygen and/or hydrogen to supply the soil with the chemical needed to grow the plants we eat, and which the livestock eat to provide us with meat.

Bacteria accomplish God’s method of nitrogen fixation. The bacteria turn nitrogen into ammonia, which is a nitrogen atom sharing electrons with three hydrogen atoms instead of with another nitrogen atom. Plants known as legumes such as soybeans and peas, as well as bayberry and alder trees, attract bacteria which concentrate in nodules on the plant’s roots. The bacteria turn nitrogen gas into ammonia and nitrates the plants can use. Cyanobacteria in the ocean and cycad plants on the land are also major nitrogen fixers. Scientists are also discovering tropical plants that contribute to the wealth of nitrogen compounds in the soil.

Most of our fertilizers have nitrogen fixed by a method called the Haber-Bosch process. It uses massive amounts of energy to break the triple bonds of nitrogen gas. Producing 500 degrees and 200 atmospheres is expensive, and that is why you pay so much for the fertilizer you use in your garden. God’s methods are free. Scientists are trying to figure out how to recreate God’s nitrogen fixation method to save energy and produce more food.

Many bacteria are beneficial in various ways, and nitrogen fixation is only one of them. This is a great apologetic for God’s wisdom and design in preparing the Earth to provide food for us to eat.

— John N. Clayton © 2020

An excellent article on this topic titled “Out of Thin Air” was published in Science News, April 12, 2008. It is available online at THIS LINK, but a subscription is required to read it.