Do you have a composting toilet kd3pc? Note that ALL composting toilets for boats separate the liquids from the solids. Only the Air Head uses a coffee filter, which you don't actually have to use. There is no odor if you use it correctly... ZERO odor. Disposing of liquids is an inconvenience. Urine is sterile- I just dump it in the sea every night. I suggest you visit a boat that has one installed to get the straight poop on it.
I have two in a self sustained cabin, one airhead branded and one before airhead name and it is as you describe. Totally odor free. Months of service for the two of us. Early units did not separate liquids and solids, and every one of them, if not minded well and often...did have issues...odors, and messes. They have come a long way.
In the US, sterile or not, it is illegal to dump the urine...overboard
I have been aboard several boats where the installation was not done as well as it should and the venting, or lack there of, causes odors...or the owner has modified the vent with fans and bends and traps...several others where they just let the liquids go in to the dry stuff....which destroys the process and causes odors, bad ones.
If installed correctly and maintained correctly, they can be an option...