You can't burn the fats whole.  http://www.dailymail.co.uk/news/article-2786560/Crematorium-set-ablaze-800lb-body-created-flames-caused-ceiling-catch-fire.html Often the drainage can't keep up with the fat fire. You've got to either have an immense setup, or do what they usually do, which is charge double, chop em in half, and burn each half. (EDIT: source: seen it, worked as medical examiner)