WARNING: THIS SECTION IS NOT FOR THE SQUEAMISH
Many people are bothered by the idea of being buried in the ground. People don't like the idea of slowly decomposing or being "eaten by worms."
Cremation, by contrast, seems quick and clean.
The truth is, though, that cremation is neither quick nor clean.
Because the oven is closed and the process is not seen, it seems as if the horrors of open-air cremation don't exist. Perhaps we prefer not to think about it.
In the chamber, nothing has changed. Let's see what actually happens to the body.
Step 1: Checking the Body
Crematory workers poke the body to check for implants, pacemakers, hip replacements, etc. All of these can damage the oven equipment and are therefore cut out by crematory workers prior to the body being inserted into the oven.
Step 2: The Burning
The oven is heated to approximately 1,800 degrees. The body moves about (1), with expansion and contraction of muscles and sinews common due to the intense heat. After a short while, the body becomes dehydrated and bursts into flames. As described by W.E.D. Evans in The Chemistry of Death:
The coffin is introduced into the furnace where it rapidly catches fire, bulges and wraps, and the coffin sides may collapse and fall, exposing the remains to the direct effect of the flames. The skin and hair at once scorch, char and burn … the muscles slowly contract, and there may be a steady divarication of the thighs with gradually developing flexion of the limbs … Occasionally there is swelling of the abdomen before the skin and abdominal muscles char and split; the swelling is due to the formation of steam and the expansion of gases in the abdominal contents. Destruction of the soft tissues gradually exposes parts of the skeleton. The skull is soon devoid of covering, then the bones of limbs appear, commencing at the extremities of the limbs where they are relatively poorly covered by muscles or fat, and the ribs also become exposed. The small bones of the digits, wrists and ankles remain united by their ligaments for a surprising length of time, maintaining their anatomical relationship even though the hands and feet fall away from the adjacent long bones. The abdominal contents burn fairly slowly, and the lungs more slowly still … the brain is especially resistant to complete combustion during cremation of the body. Even when the vault of the skull has broken and fallen away, the brain has been seen as a dark, fused mass with rather sticky consistency, and the organ may persist in this form for most of the time required for the destruction of the remains … Eventually the spine becomes visible as the viscera disappear; the bones glow whitely [sic] in the flames, and the skeleton falls apart. Some bones fragment into pieces of various sizes while other bones remain whole. (2)
Put simply, cremation is not peaceful, quiet, or calm. It is a harsh, odorous (3), loud act of violence committed against the body of a human being, a recently deceased loved one.
Step 3: The Separation
Once the burning is complete and the remains cool down, bone fragments are separated from the rest of the remains. A simple (or blue-collar) crematory worker sifts through the remains by hand with a magnet to separate out any non-bone material such as dental fillings, bridge work, hip joints, etc.
Step 4: The Grinding
Next, the bone fragments are swept out and the crematory operator "processes them" into fine granules. Alternatively known as pulverizing or grinding, these processors use a rotating or grinding mechanism to chop the bones down to very fine powder.
Perhaps repulsed by the idea of grinding Grandma, the ancient Greeks and Romans did not pulverize bones, thus explaining why their urns were larger than modern ones. Today, grinding is standard practice in the United States and Western Europe.
Conclusion
Some people are squeamish about burial. Certainly, decomposition is not pretty to contemplate. However, decomposition is a natural process that occurs to all (formerly) living beings. Though not pretty, it is the natural way of the earth.
Cremation, on the other hand, is loud, violent, disgusting, and artificial.