Nitrogen extraction is one of the most important aspects of our modern economy. However, the environmental impact of the Haber-Bosch process may no longer be sustainable.

100 years have passed since Fritz Haber patented his nitrogen transformation technique that changed the world for the better. However, the process also left indelible scars on the world’s environment. Now, a panel of experts in nitrogen research calls for carbon-free transformation techniques of nitrogen.

Nitrogen is a gas that constitutes 78% of the volume of the Earth’s atmosphere. Simply put, it’s everywhere.

The abundance of nitrogen in the air, however, doesn’t mean that it’s readily available for living beings whose life depends on the nitrogen cycle.

Humans and animals get their nitrogen from proteins in food while plants absorb nitrogen in its mineral form as nitrates from the soil.

Life-giving nitrogen is all around us, yet unattainable.

The Nitrogen Cycle, Simply Explained

The nitrogen cycle plays a vital role for the biosphere as nitrogen compounds like proteins, enzymes, and hormones are all fundamental constituents of organic matter.

The nitrogen cycle starts with “nitrifying microbes” that transform nitrogen gas by combining it with hydrogen to produce ammonia.

In the soil, nitrobacteria break down ammonia into nitrite and nitrate in a process known as nitrification.

Nitrification allows plants to incorporate nitrogen into their metabolism before they are consumed in turn by higher organisms in the food chain.

Animals (and humans) release nitrogenous wastes while alive and, after their death, the nitrogen content in their body reintegrates the soil.

In contrast to nitrifying bacteria, there are also bacteria that act as “denitrifiers” that allow nitrogen to return to the atmosphere.

And the nitrogen cycle is thus closed.

In the sea, some types of algae take over the nitrification/denitrification role played by bacteria.

This is the natural nitrogen cycle that, as is nature’s method, doesn’t leave any loose ends. All living creatures abide by nature’s rules except, of course, us humans.

The “Artificial” Nitrogen Cycle: Nitrogen as a Commodity

We humans need nitrogen not only to survive but also to make our life a bit easier.

Since the Haber–Bosch process was invented, nitrogen has been used to fertilize soils, which is beginning to take a serious toll on the environment.

Read More: Why Have we Been Using Nitrogen Fertilizers?

We also release toxic compounds into the atmosphere in the form of nitrogen dioxide by burning fossil fuels. This eventually comes back to us in the form of acid rain.

The toxic nitrogen byproducts go beyond the combustion of fossil fuels to run our cars and factories. The production of industrial nitrogen itself requires lots of pollutant fossil energy.

To obtain nitrogen industrially, air is liquefied and then subjected to fractional distillation to separate the oxygen and extract liquid nitrogen.

Producing nitrogen through this technique isn’t very efficient in that it leaves impurities in the liquid nitrogen as the oxygen can’t be fully removed.

Also, this widely used technique is energy-intensive. Currently, 2% of the world’s energy output goes into nitrogen transformation into ammonia.

Carbon-Free Nitrogen Transformation Techniques

The Haber-Bosch process, invented almost a century ago, enabled the green revolution that helped sustain growing populations and change the world.

In fact, we can find some of the HB process’ lasting-effects on us, or more exactly, inside us.

According to a review paper in the last issue of Science journal, half the nitrogen atoms in our bodies today comes from the Haber-Bosch process.

The article, “Beyond fossil fuel–driven nitrogen transformations”, was collectively written by several American experts in nitrogen research.

At the behest of the U.S. Department of Energy Office of Basic Energy Sciences, a team of 16 chemists and biochemists from different American universities gathered to discuss our current situation and prospects of the nitrogen industry.

The world has become too reliant on a nitrogen-based economy thanks to the Haber-Bosch process and the flip side is a warming planet. Naturally, this isn’t a process that we can sustain for much longer.

Lance Seefeldt, a biochemist at Utah State University and one of the article authors, says:

[the HB process] was one of history’s technological marvels, but it currently consumes about two percent of the world’s fossil fuel supply and thus, it’s come with a very heavy carbon footprint.”

There’s an urgent need to find more eco-friendly ways to industrially harvest atmospheric nitrogen without compromising the integrity of the environment and biodiversity.

The team thinks it’s time to prompt a radical change:

“Opportunities exist to achieve radically improved, new and different pathways (to achieve nitrogen transformations). But progress in this regard will require a molecular-level understanding of nitrogen transformation reactions, as well as … discovery of new catalytic systems and alternative means of delivering the energy needed to drive those reactions.”

Progress is slow, and it’s certain that nitrogen-based fertilizers will still be used for years to come. But, for us to maintain this scale of agricultural growth, new nitrogen extraction methods need to be discovered through more carbon-neutral means.

How can the Haber-Bosch process be modified, or replaced, for sustainable nitrogen to ammonia conversion?

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