For his part, Mitchell believes the more likely culprit is ammonium nitrate.

Several days after the blast, investigators discovered the plant was storing 1,350 times the amount of ammonium nitrate required for oversight by the U.S. Department of Homeland Security (DHS).

Fertilizer plants and depots must report to the DHS when their inventory of the substance reaches 400 pounds or more.

“We’ve known since the early 1900s when we first began manufacturing nitrogen fertilizer that ammonium nitrate is, potentially speaking, a very combustible substance, used in the first bombing of the World Trade Center in 1993, the Oklahoma City Bombing in 1995 and in the improvised explosive devices (IEDs) used to kill to many people in Iraq, Afghanistan and other regions of the world,” Mitchell says. 

“If this is true and the plant stockpiled this much ammonium nitrate, it certainly could account for the huge fireball seen 40 miles away and the earthquake-like jolt that was strong enough to register on the Richter scale,” Mitchell says.

However, since the Oklahoma City tragedy, the federal government has undertaken strenuous efforts to limit of availability and use of ammonium nitrate.

Consequently, there is little incentive for small farmers, much less, home gardeners to use it.

“Today, small farmers and gardeners would find it difficult, if not impossible to find it,” Mitchell says. “Small fertilizer companies simply don’t carry it because of the security and reporting requirements associated with it.”

On top of that, transporting more than 1,000 pounds of it requires a special permit — and 1,000 pounds is only enough to fertilize two acres of corn.”

While some farmers think they may be purchasing ammonium nitrate, the vast majority of fertilizer used on Alabama crops is a blend of urea and ammonium sulfate, which can be used just like ammonium nitrate, Mitchell says.

“Unlike ammonium nitrate, though, this is not an oxidizer, meaning it will not explode,” he says.

Mitchell says Alabamians who live near fertilizer dealers should rest comfortably, because no dealer in the state handles anhydrous ammonia and only very few still stock ammonium nitrate, and even then only in small amounts.

The only ammonia plant in Alabama is near Cherokee, located in the northwest corner of the state.

Even so, Mitchell is concerned that the recent incident will generate unjustified fears about fertilizer transportation, storage and use.

Mitchell’s colleague, Frank Owsley, an Alabama Extension specialist and Auburn University professor of animal science, worries that the recent incident will only worsen the deepening divisions along what he describes as the urban/rural interface, the regions of the country where sprawling subdivisions are rubbing up against farmland, pastures and forestland.

The explosion not only destroyed 75 homes but also a local school and nursing home, all of which were established after the fertilizer plant was built in 1957.

“People who want to escape the hectic life of the big city have a right to build homes and live in or near areas where farming has traditionally been the cornerstone of the economy,” Owsley says.  “On the other hand, they must understand that farms and ranches operate within a larger economic infrastructure, which includes stockyards, dealerships, and, in some cases, fertilizer plants.”

Mitchell says Americans also should remember that the industrial process of ammonia manufacture, developed in 1913, is responsible for feeding 3 out of every 4 people today.


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