One of the urban myths floating around about Wankel rotaries
is they are dirty when it comes to emissions.
Nothing could be further from the truth.
Here is the smog paperwork on my 2004 RX8.
Certain info has been redacted to protect the innocent.

Note that CO2 is zero or less than .1%. Too little
to measure.

HC are zero parts per million.
CO is .06 PPM.
NO is zero parts per million.

Mazda could lean this engine once in a while
to reduce the fuel burn and still keep NO
under the allowable 724 parts per million.
I have monitored the OBD II and it never
ever goes lean unfortunately. My Honda Odyssey
does in fact go lean from time to time.

All this is despite the fact I add a 1/2 oz of 2 cycle oil
to the fuel to better lube the apex seals. Rumor
has it early 2004 RX8 cars did not have enough apex lube
from the computer controlled metering pump.

Bottom line is Mazda over did it in the smog department.

Paul Lamar