Crematoriums run at ~1600 degrees F. It takes roughly 2.5 hours to burn off organic matter (still leaving behind bones and teeth that then must be crushed in a separate process).

Heat Energy (calories) = m * c * ΔT m = mass of human ( average: 80.7 kg )

c = specific heat of human body ( 3470 J. kg-1 . K-1 )

ΔT = Change in temperature. ( cremation temp - room temp )

Room Temperature = 26 °C

1600 °F = 871°C

So: H.E. = 80.7kg * 3470 J/kg*k * (871-26)

H.E. = 236624.5 kcal

The energy in a kg of coke(coal) is 8000 kcal/kg. So one body would (under IDEAL conditions) take 236625kcal/8000kcal/kg = 29.57 or about 30kg (66 pounds!) of fuel to burn.

To cremate say 3-6 million jews, therefore, it would take around 100,000-200,000 metric tons (220,462,280-440,924,560 pounds!) of coal.

That is an awful lot of coal (i.e. impossible) for a country that couldn’t heat its homes, operate its tanks or fly it's aircraft etc. because of beyond-critical fuel shortages.

Also when coal is burnt, it generates around 5-10% of its weight in ash. So, I'll be generous and say 5%. So 9 million kg of ash from the fuel. The average adult leaves ~2.5kg of bone fragments, teeth and ash from cremation. So we have 9 million + 2.5x6million = 24 million kg of ash.

That is a lot of remains to just disappear and leave no trace. Makes one think.