Pure speculation on my part, but maybe that's better for the environment because it's not being burned as it's used?

Make the airplane light for landing. Many large aircraft takeoff heavier than their max landing weight.

They burned twice that much fuel getting the plane into the air, flying an hour and a half, then having to turn back.

It'll turn into CO2 eventually. For now, it's just contributing to smog.

Well, having the plane crash and catch on fire upon attempt at landing would have been substantially worse for the environment.

Of course it's true its better than crashing. It's just if we go up the chain of events perhaps better restraints or a checklist could have prevented this altogether. I wonder if they do post-mortems in logistics

"I wonder if aviators do post-flight debriefs." Good gravy. This is like your nontechnical relative saying "my cousin is good with computers; how hard can programming be?"

What about the cargo loaders? Unless you think the pilots loaded the horses?

Sigh . . . Donny, you're out of your element.

Once they sign for the aircraft, the pilot in command is legally responsible for all aspects of safe aircraft operation regardless of who did what work before.

That's just, like, your opinion, man.

dumped where/how?

If it makes you feel better, owing to kerosene being highly volatile, the conventional wisdom is that at or above 5,000 feet something like 98 percent of it will have evaporated by the time the remainder reaches earth, by which point it will have been spread out over a large area.