Half a century ago carcases were flung on the muck heap and mixed in by front loader. No attempt was made to prevent run-off, of which there was plenty. I'm not convinced that sawdust would prevent run-off of the large amount of liquid produced by a decomposing whole adult animal, although if it's in the middle of the heap it might just drain downwards - into the watercourse? I suspect also that the appropriate organisms needed for total and efficient decomposition would not be at home in sawdust. Proper burial underground would still be preferable, although in Britain we now have a good incineration industry. The potential fertility of decomposition is lost during incineration of course, but is preserved in both burial and this composting process.