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Editorial: Greening the farm, with chemistry

by Michael McCoy
July 30, 2023 | A version of this story appeared in Volume 101, Issue 25


Sprinkle some Scotts Turf Builder on your lawn, or scoop a bit of Miracle-Gro into water for your houseplants, and you might think fertilizer is a clean, benign substance. Of course, it’s not. Manufacturing the synthetic fertilizers that help farmers feed the world is an energy- and resource-intensive process that stresses our air, land, and water.

Take phosphate fertilizers. In the US, large swaths of Florida and North Carolina have been denuded to remove phosphorus-rich rock from the ground. This phosphate rock is reacted with sulfuric acid in huge quantities to produce phosphoric acid, which is then combined with ammonia to produce ammonium phosphates, the main class of phosphate fertilizer.

In the process, the sulfuric acid reacts with fluorine in the rock to yield hydrofluosilicic acid. Some of this chemical is purified to become the fluoride in our drinking water, but most of it is neutralized and released into the sea.

Producing phosphates is particularly damaging to the environment, but making nitrogen and potassium fertilizers is also resource intensive. We’ve been using the same processes for decades, and they don’t seem sustainable.

In this week’s cover story, reporter Matt Blois writes about a new kind of microbial fertilizer intended to replace ammonia and other synthetic forms of nitrogen (see page 24). Most chemists know that ammonia is produced commercially from diatomic nitrogen and hydrogen using the Haber-Bosch process. As Blois reports, making and using nitrogen fertilizers is, by one estimate, responsible for 5% of all greenhouse gas emissions.

I’m definitely taken by the idea of engineering microbes to generate plant-accessible forms of nitrogen in quantities greater than bacteria typically make in nature. It’s cool, though Blois’s story makes clear that not everyone is convinced the approach works very well.

I’m also a little disturbed by the idea of releasing these microbes into the wild by spreading them across the farms of the US Midwest. I will have to trust that our regulators acted wisely in giving the technology the green light.

Traditional chemistry can also play a role in making agriculture more environmentally palatable. Blois earlier reported about the start-up Nitricity, which is using a solar-driven plasma reactor to turn diatomic nitrogen into a nitric acid solution for fertilizer use.

And I wrote a story in 2020 about a project by the fertilizer maker Nutrien and the chemical company Arkema to capture some of the hydrofluosilicic acid from phosphate fertilizer production and convert it into hydrofluoric acid, the starting point for most fluorine-based chemistry.

We’ve covered other cool applications of green chemistry on the farm, including DSM’s 3-nitrooxypropanol, which is added to the feed of dairy cows to inhibit an enzyme and reduce the amount of methane that cows create while digesting their food. Evonik Industries has invested in a start-up called In Ovo that uses mass spectrometry to distinguish the sex of chickens while still in the egg. In Ovo wants to stop the poultry industry’s grisly practice of killing most male chicks because they don’t lay eggs.

Lots of people argue that the antidote to the ravages of industrialized farming isn’t more technology but rather a return to more holistic, preindustrial practices. It’s a quaint idea (and we definitely shouldn’t be eating so much meat), but this planet has over 8 billion people today. Small organic farms aren’t going to feed us all.

Meanwhile, I was recently heartened by news from Mosaic, one of the world’s largest phosphate fertilizer producers. In January, the company reported making $160 million from selling a Florida golf course it built on top of a former phosphate mine. It turns out that the pits Mosaic left behind could be turned into the dunes, bunkers, and lakes that golfers love.

I’m taking the sale as a small piece of evidence that we can help Earth heal after we’ve damaged it. I hope, with new technology, that the healing can continue.

Views expressed on this page are those of the author and not necessarily those of ACS.


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