Yeah, I have major problems with this also... not an expert in body disposal, but one thing I distinctly remember from discussions on the topic, is that "it takes a lot of heat to reduce a body to ashes". Bonfires won't do it; cremation ovens are set super high for a reason. Plus it would stink to high heaven, as others have pointed out.
I think that is somewhat of a misnomer.
Unfortunately, through the years we have seen several cases where the victim's body was burned by the murderer, and all LE was able to recover were ashes, and charred bone fragments.
Some accelerants like gasoline being poured directly on the body itself can reduce the remains to a ashen, and a fragmented state. It burns at a very high heat, and if it is repeatedly put on the remains it burns even faster.
That is how many farmers, and ranchers cremate dead animals. It is very doable when consuming the remains. It doesnt take that long either as some may think.
An example in a recent murder trial was when Daron Wint poured gasoline directly on 10 year old Philip in his midsection setting him on fire.
The fire had not been started for that long either before the neighbors saw the smoke, and from when the fire department came, and put the fire out.
However when little Philip's autopsy was done only the top half of his body was there , but from his midsection down was completely destroyed, and gone from the accelerant which was gasoline.
Jmhoo
I have a Kia Optima. Doesn't mean I'm any less of a human!