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University of Miami Chemists Find Green Way of Producing Fertilizer

University of Miami chemistry professor Carl Hoff stands with one of his grad students, as both wear masks, in front of a Retsch MM500 machine.
Kristin Moorehead
University of Miami chemistry professor Carl Hoff stands with Oswaldo Guio, one of his graduate students, in front of a Retsch MM500 machine.

As we head into the South Florida rainy season and the first year that Miami-Dade County has banned fertilizer to help improve Biscayne Bay, University of Miami chemists are looking at another way to clean up fertilizer — by changing how we make it.

UM chemistry professors Carl Hoff and Burjor Captain worked with two graduate students to discover a way to improve the production of fertilizer.

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The traditional method of producing fertilizer is called the Haber process. It was invented by Fritz Haber and Carl Bosch in Germany during World War I. Their discovery of using nitrogen in the air to create ammonia used in fertilizer won them Nobel Prizes.

This process has become the industry standard, but it’s not perfect. The method involves the burning of fossil fuels or coal for energy, and produces chemical byproducts that are toxic to the environment and contribute to climate change.

“About half of the hydrogen produced in the United States is used to make fertilizer. So that’s a huge amount of energy. If you save 10% of the energy used in making fertilizer, that would be a really significant thing,” Hoff said.

However, Hoff and Captain have discovered a way of using byproducts of the Haber process to create more fertilizer using greener energy. The process involves a machine called the Retsch MM500. This machine grinds materials into super-fine nanoparticles that absorb gas.

After about six days of continuous mixing, the chemists are able to convert the pollutant nitrous oxide — commonly known as “laughing gas” — into a usable component found in most modern fertilizers.

“I like to say our process is faster than a compost heap,” Hoff said.

Hoff and Captain said they applied for a provisional patent for their process. They hope to renew their funding grant from the Department of Energy to continue their research.

Kristin Moorehead is a 2021 WLRN summer intern and recent graduate of the University of Florida with a B.S. in Telecommunication.