One thing could be methane from improperly stored manure waste. Not sure if that facility used anhydrous ammonia on crops, or even if they grew their own feed crops.
Still trying to figger out what blew hard enough to kill 18K cows. The Texans do indeed know how to blow up a load of fertilizer. Remember in the 1940’s that French ship was taking on a load of nitrate in Texas City and blew the whole thing up? But that was a ship load.
Really hard to visualize a dairy keeping enough dry nitrate in one pile to do that much damage? Most agricultural uses liquid fertilizer now which doesn’t do that anyway. And that black smoke we saw had more than fertilizer and cow hide in it?
Maybe the cows were getting new shoes and their recap machine blew?