Until people become educated on the subject, unreasonable fears such as Heart's Content is exhibiting will continue and serve to hold back simple solutions such as special bins provided by municipalities for the specific purpose of collecting compostable materials.
The sad fact is that misinformation is holding back progress. People like HC are sitting on city councils and making decisions based on paranoia rather than science.
However, to answer your question directly. Placing the mostly dry contents of a composting head into a stout plastic trash bag and tossing it in the dumpster seems to work for a lot of people. It will still end up in the dump and be returned to the soil. And it won't be any more dangerous than all the diapers that end up there.
a. Is there something better about a cruiser depositing night waste mixed with saw dust in a waste can than disposing of sewage into a sewage treatment plant? To my mind, they are perhaps equal. Both are acceptable with some negatives.
b. The solids are not composted in the airhead of a well used boat--the design is inadequate, the temperatures too low and the rate is too high--they are only partially dried and mixed with stuff. Put the solids in my yard to compost? Like many sailors, that is 1-hour drive from the boat and I'm not trucking it home. There is no "green" disposal possibility anywhere I have ever
cruised. So, while "humanure" might work for some--and I think it is an acceptable idea where there are good composting practices--it simply will not work for most sailors.
c. A properly installed marine head has zero odor; it's a matter of proper installation. There are many old systems that don't work, but likewise there are many old cars that don't run. They're not hard to fix, but perhaps it's not obvious. Proper hoses. Proper venting (large or a filter). Short hose runs. Proper design. I was on my boat today, and it worked just as well as my home facility.
d. Risk of sinking. My through hulls are in a bulkheaded compartment. I don't have siphon breaks, as the head is 4" above the water line and catamarans don't heel much. Really, no risk of sinking in my case. Yes, there are some scary through hull installations out there.
e. As for comments that everything will eventually fail, well, obviously. Air-head sell spare parts too, and from what I'm told, things do break. I over-hauled my MSD system this summer, after 14 years, and it's like new. That seems pretty reasonable. Not difficult. Like "a", this issue is probably equal either way.
f. Hauling crap out vs. pumping-out. Pumping out is really easy in most areas, like getting gas (often the same dock). Hauling crap means carrying something through the salon, down the dock, to a can, and back. And pitching the piss each day. I don't have a poo phobia, not at all. I just know which system is easier.
g. psuedo-composting head needs continuous power. Fan wears out. Danger of fire. Small, but so is sinking.
h. Psudo-composting head needs large vent; if poorly installed these can REALLY take water, drowning the above fan and wetting compost. It's happened. A vent design error on an MSD system only fills the tank, and that is rare.
Yes, a pseudo-composting toilet can work. But I don't believe the case has been made that it is better for most sailors. Some will like it, but not very many. A bucket can work and so can a smelly poorly designed MSD. I offer that most air-head buyers are reacting to a bad msd expereince, rather than choosing with a clear head.
PS. I have designed commercial composting operations (yard waste, presorted household waste, rendering waste), sewage treatment plants (both refinery waste and sanitary waste) and oil and metals recycling facilities: I am neither paranoid nor ignorant.