Cuts from EPA correspondence
As you know, pyrolysis units are not subject to the HMIWI regulations (see, 40 CFR 60.32e (f) and 40 CFR 60.50c (f)). In the regulations, pyrolysis is defined as “the endothermic gasification of hospital waste and/or medical / infectious waste using external energy” (see, 40 CFR 60.51c). In the preamble to final HMIWI regulations, USEPA noted that:
Pyrolysis technology is different from conventional incineration. Because air is generally not used in the pyrolysis treatment process, the volume of exhaust gas produced from pyrolysis treatment is likely to be far less than the volume of gas produced from the burning of waste in an HMIWI. Although conventional combustion does not occur during pyrolysis treatment, there are some emissions from the pyrolysis process (see, 62 Fed. Reg. 48358).
There are a number of noteworthy, additional differences between pyrolysis technology and conventional incineration.
First, pyrolysis technology is an endothermic reaction (absorbs heat) while combustion is an exothermic reaction (releases heat). Second, pyrolysis occurs in the presence of an insignificant amount of oxygen. Third and finally, pyrolysis has an external energy source.