First, the question of the whether there's any evidence that decomposed bodies burn much more easily than fresh bodies. ANTPogo has still not offered any empirical evidence for this claim. If you have any such evidence, ANTPogo, you should present it; if not you should admit that you do not.
ANTPogo does quote a passage from Muehlenkamp on the energy content of decomposition byproducts. It does not, however, refute any of my arguments, and it illustrates Muehlenkamp's total ignorance of decomposition beyond what he scratched together with a few google searches.
First among Muehlenkamp's errors is that he relies on sources about decomposition on the surface when he should be studying decomposition in deep mass graves. He uncritically parrots categories (his stages of decomposition) that do not apply there. In fact, his stages of decomposition are not even some kind of general truth about decomposition on the surface, but only the way in which one source has decided to break things up. In particular his much beloved "phase of butyric fermentation" is not much mentioned in the actual published literature on the subject.
The fact that ANTPogo can cite a energy value of 16 MJ/kg for glycerol as evidence that energy content does not decrease with decomposition is proof that he knows nothing about this subject. Human fat has an energy value of ~39 MJ/kg. As 16 is quite a bit less than 39...
Muehlenkamp's utter ignorance is also revealed by the fact that he refers to
the fat's breaking down into glycerol and fatty acids [249] (namely the butyric acid [250] that leads to this stage also being characterized as butyric fermentation)
as though butyric acid [butanoic acid] is the main fatty acid involved; in reality it is not, but just one of the principal
volatile fatty acids (aka short chain fatty acids). This means that it is important in forensics, for instance because it has a strong smell and is relevant to detection by cadaver dogs. But this tells us nothing about burning decomposed bodies, and in absolute terms butanoic acid is a rather minor factor.
As for "this stage also being characterized as butyric fermentation", first of all this is not a standard term accepted in the literature generally. Second, when the term is used it has to do with butyric acid's role in creating a
smell, nothing more. Third, all of this discussion of stages is meant to apply to decomposition on the surface, not decomposition in deep mass graves. To learn about how bodies decompose in mass graves, you need to look at how bodies decompose in mass graves. Study, for instance, the condition of the bodies exhumed from the graves at Katyn - an example which has the added benefit of being located in sandy soil in Poland, just like Treblinka or Belzec. Muehlenkamp avoids doing this, because the data refute his tendentious speculations about decomposition.
Now, on the matter of burial space, ANTPogo writes:
I see, from Carcass disposal: a comprehensive review that there's quite a large disparity in volumes required per carcass as listed in various sources.
For example, it says "Based on the information in Table A2, estimates of the required excavation volume to accommodate mature cattle carcasses include 1.2 yd3 (McDaniel, 1991; USDA, 2001a), 2 yd3 (Agriculture and Resource Management Council of Australia and New Zealand, 1996), 3 yd3 (Lund, Kruger, & Weldon), and 3.5 yd3 (Ollis, 2002)."
That gives a range of .9 m3 to 2.7 m3 required per cattle carcass, neatly illustrating the problem with relying on modern public agency guidelines about animal carcass disposal.
I never asserted that 0.3 cubic meters per body was a strong upper bound, but only that it was a reasonable estimate. The true value could be somewhat higher or lower. For example, one of the main Buchenwald witnesses claimed (see Nuremberg document NO-1253) that during the last weeks of the camp's existence there was no fuel for the crematorium, so that burial pits had to be dug; these were 15 meters long, 6 meters wide, and 4 meters deep, and held 400-600 bodies. That's 400-600 bodies in a volume of 360 cubic meters. With the higher figure of 600 bodies that's 0.6 cubic meters per body, and with the lower figure of 400 bodies that's 0.9 cubic meters per body. In either case, it's quite a bit higher than the estimate of 0.3 cubic meters per body which I offered.
And at the lower number there, .9 m3 per cattle carcass (since 1 cattle carcass is equivalent to 5 sheep carcasses according to "several sources") means that a pit of the dimensions being described could hold just a shade under ten thousand sheep carcasses, a 166% increase over your calculated number, and only 60% of the volume per carcass as the figures you cite.
Mathematics is not your strong point - this is not a 166% increase, but a 66% increase (rounding to 67%, actually). But I'm happy to take the lowest number here, if you like. Let's assume 5 Jews per 0.9 cubic meters; that means that 1,768 cubic meters could hold roughly 9,800 Jews. So where were the other 750,000 buried? The pits that Sturdy-Colls has reported are totally inadequate for the alleged burial, even if we assume that every bit of disturbed soil corresponds to a burial pit. Of course, we know that not all of the pit volume at Treblinka represents graves - consider the large bomb crater reported by Judge Łukaszkiewicz, or the digging carried out by local "treasure hunters".