Jun 06, 2020

Information key to keep fertilizer plants safe

Residents of the agriculturally rich Valley were reminded on April 17 that fertilizer is not just the unpleasant ingredient to a bountiful crop or garden it — can be explosive.

The small town of West, Texas, about 20 miles north of Waco, was like any other small town that has a fertilizer plant before that night. It might smell at times, but other than that, the thought was there was nothing to worry about.  

Then a fire started and a chain of events that is still under investigation led to a massive explosion that left buildings flattened and an estimated 14 people dead.  It was so powerful that it registered as a small earthquake.

The plant produced ammonium nitrate, which is commonly used as a fertilizer and has high nitrogen content. Nitrogen is used to enrich soil and happens naturally, but the natural process on its own is too slow and is stimulated with fertilizer, said Fresno State inorganic chemistry professor Melissa Golden.

Ammonium nitrate is stable typically and is produced on a massive scale worldwide, Golden said.  However, when ammonium nitrate is exposed to high temperatures, it can become explosive.

There is more energy stored in the chemical bonds of ammonium nitrate than when broken down into nitrogen gas, oxygen gas and water in the gaseous form, Golden said.  When that process occurs, the extra energy has to go somewhere, and heat can greatly accelerate the release of energy.

“That’s where the heat comes out,” Golden said. “The heat encourages that reaction it gives it enough energy to get that reaction started.  You increase the temperature of the gasses, they are going to expand and the more gas you have the more pressure is going to build.”

The result is a before-and-after picture of small town that looks like it was bombed in a war.

Firefighters and emergency services that responded to the fire in West bore the brunt of the explosion when it occurred, with at least 11 first responders dying in the blast.  For Capt. Ryan Michaels, spokesman for Cal Fire/Fresno County Fire, the best protection for firefighters in this situation is information.

“There are a lot of hazardous chemicals stored throughout Fresno County,” Michaels said.  “As long as we are doing inspections, evaluating and looking at what we are up against, it will increase the safety margin we have.  The unknown is what is so dangerous.”

Michaels said an inventory is updated with locations that have dangerous chemicals on site to give first responders as much information as possible.

Ammonium nitrate is just one item on the list of potential chemical hazards that firefighters have to be prepared to meet on a given call to a fire.

“Ammonium nitrate can be volatile, but it is not the worst chemical out there,” Michaels said. “When we respond, hopefully we know what we’re up against and change our tactics. We may take a more defensive approach, but it is on a case-by-case basis.”

In the end, the accident was another reminder for Michaels that danger is always present, whether you are fighting a fire in Fresno County or a small town in Texas with fewer than 3,000 people.

“Those types of incidents can happen anywhere,” Michaels said. “It does make you reflect on what you are up against every day.”

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