The RePercussion Section: On Fracking and Food, Part 1
by Sandra Steingraber, SEHN senior scientist
This essay is the first of two on climate change and the fertilizer crisis. Next up: Green Hydrogen: Promise or Peril?
Here is a column about how our food ended up riding a tandem bicycle with fracking. But first, breaking all the rules of popular science writing, I’m going to begin with a chemistry lesson.
Let’s talk about nitrogen, which occupies box #7 in the periodic chart of elements.
We all desperately need nitrogen to stay alive. Nitrogen atoms are core components of our genetic material (DNA and RNA) and they are also a key ingredient of amino acids, from which we make all the protein parts of ourselves (under the direction of DNA and RNA), and they also are needed for the synthesis of ATP, which provides us the calories to run all of the above.
You somehow remember the Krebs cycle, right?
Given all that, it might seem like good news to learn that nitrogen comprises almost 80 percent of the air that we breathe into our spongy lungs. More specifically, Earth’s atmosphere is 78 percent nitrogen and 21 percent oxygen (plus one percent other stuff, including hydrogen and carbon dioxide).
Oxygen, of course, is nitrogen’s next-door neighbor, inhabiting box #8 in the periodic chart, and it’s snatched up immediately by the hemoglobin in our red blood cells as soon as it arrives in our lungs. Within a minute of its inhalation, oxygen enters the mitochondria of our cells where it’s put to work breaking apart carbon bonds and releasing energy.
By contrast, we can use exactly none the nitrogen that we breathe in. It just gets exhaled right back out again. And that’s because airborne nitrogen atoms prefer to pair up with themselves, and those N2 molecules are notoriously unreactive, glued together by inflexible triple bonds. *(1)
Plants have it even tougher. Not only do they need nitrogen for nucleic acids, amino acids, and ATP, plants also require nitrogen for chlorophyll, which captures the energy in sunlight to make food via photosynthesis. Nitrogen deficiency in plants looks like slow growth and yellow leaves.
Plants, like animals, cannot just snatch nitrogen out of the air. Instead, out in the ocean, photosynthetic plankton—rootlessly surfing the sunlit surface of the waves—rely on upwellings to bring them nitrogen-rich fish poop (officially “marine snow”) that would otherwise fall to seafloor. Fish poop is Miracle Grow for plankton stocks. Plankton, in turn, provides us half the oxygen we breathe.
Here on land, rooted plants source nitrogen from the soil, where its atoms are bonded to oxygen (nitrates) or hydrogen (ammonium) in chemical combinations that are easier for plants to break apart and manipulate. On land as out at sea, animal poop is a key part of the nitrogen cycle: fungi, worms, and other decomposers turn organic waste plopped out onto the earth’s surface into ammonia. Soil bacteria then convert ammonia to nitrates, which plant roots can easily assimilate.
Land plants have a second trick up their green sleeves. Some plants (legumes) have the ability to construct little housing projects on their roots to quarter nitrogen-fixing bacteria. These microbes possess enzymes capable of pulling N2 molecules apart from each other by offering them free electrons, thus coaxing nitrogen atoms into bonding with hydrogen and making ammonia.
How plants make ammonia from nitrogen molecules: root nodules in legumeceous plants house nitrogen-fixing bacteria equipped with special enzymes.
It turns out that pair-bonded nitrogen molecules floating so abundantly in the atmosphere are not entirely monogamous. They can be convinced to swing with hydrogen, oxygen, or carbon if enough electrons are involved and if the molecules are lined up and held by enzymes in just the right position. It takes a lot of ATPs to accomplish this feat.
Thus do nitrogen-fixing bacteria living in the root nodules of legumaceous plants pay rent to their photosynthesizing landlords in the currency of useable nitrogen.
Okay, who really knows how they imagine their symbiotic relationship. What we do know is that nitrogen-fixing bacteria typically and generously make more useable nitrogen compounds than their plant hosts need, and the remainder fertilizes the soil for all kinds of other plants. Which is why it’s good agricultural practice to rotate soybeans, which possess bountiful root nodules for the nitrogen-fixers, with corn, which is greedy for useable nitrogen but is hapless at striking deals with other organisms to make it for them.
* * *
World War I created multiple domestic problems for its aggressor, the nation state of Germany. One of them was supply chain problems created by Allied blockades, and one of the most vexing of these was its severed connection to saltpeter from the desert coastline of South America, cutting off Germany’s access to sodium nitrate. Also known, tellingly, as white gold.
At the beginning of the 20th century, natural deposits of pure sodium nitrate mined from the Atacama desert of northern Chile—and created through some kind of chemical wizardry involving sea spray, extreme aridity, and torrential rain cycles—were providing 80 percent of the nitrogen used for manufacturing commercial fertilizers around the world.
At this point in human history, Chilean saltpeter had already replaced guano deposits (nitrogen-rich bat feces) mined from Peruvian caves, which had previously held the title as the world’s number one source of useable nitrogen for industrial fertilizers. Guano supplies were exploited to depletion by 1870.
The lack of Chilean saltpeter created for Germany not only a fertilizer shortage for its farmers but a munitions problem as well. And if that seems odd, consider that the bomb that destroyed the Oklahoma City federal building in 1995 was derived from nitrogen fertilizer. Sodium nitrate is not just used to grow crops, it’s also a key ingredient of gunpowder.
Nitrogen both feeds people and blows them up.
Faced with two problems, the German chemists Fritz Haber and Carl Bosch went to work figuring out a way to get nitrogen atoms floating around in the air as triple-bonded molecules to forsake each other and conjugate with hydrogen.
The result was the Haber-Bosch process, which does not at all mimic the methods of nitrogen-fixing bacteria humbly living in the root nodules of pea plants, but instead relies on immense pressure and brutally high temperatures (840 degrees Fahrenheit) to convert atmospheric nitrogen to ammonia by reacting it with hydrogen in the presence of a metal catalyst.
Natural gas is the source of the hydrogen atoms used in the Haber-Bosch process. (Natural gas = methane = CH4.)
In 1920 and 1932, Haber and Bosh were awarded Nobel Prizes for discovering how to synthesize ammonia, the starting point for all nitrogen fertilizers.
It seems important to say here that Fritz Haber is also known as the father of chemical warfare. Haber is the scientist who developed and weaponized chlorine gas for use on the battlefield. Same guy.
* * *
Here’s the even more astonishing part of the story: More than a century later, the Haber-Bosch process is still the dominant method for making nitrogen fertilizer. Which is to say, almost all commercial synthetic fertilizers are created using natural gas as a hydrogen feedstock, and more than 70 percent of the ammonia so created is used for fertilizer. Nitrogen fertilizer is a petrochemical.
How the chemical industry makes ammonia from nitrogen molecules: The Haver-Bosch process in action.
Whereas household ammonia is a water-based solution, the signature white tankers pulled through Midwestern fields contain anhydrous ammonia. Anhydrous means without water, and, because the boiling point of anhydrous ammonia is below zero, it must be stored under high pressure. The white paint on the pressurized tanks keeps the temperatures low.
What those tanks contain is among the most energy intensive products on earth that contributes significantly to the climate crisis. The manufacture of nitrogen fertilizer alone consumes two percent of the world’s energy and is responsible for three percent of global carbon emissions. Manufacturing ammonia consumes, all by itself, five percent of the world’s natural gas supplies. (About 40 percent of the gas is used to supply the hydrogen atoms; the rest of it is burned to generate the necessary heat.)
Hence, the price of fertilizer rises and falls with the price of natural gas. And, hence, with hydraulically fractured shale wells now producing at least 79 percent of U.S. natural gas, our food rides a tandem bicycle with fracking.
Look for Part 2 in our July newsletter!
*(1): The chemical properties of nitrogen are explained elegantly by geologist Robert Hazen in his book, Symphony in C: Carbon and the Evolution of (Almost) Everything (W.W. Norton, 2019). See especially pp. 176-177.