The best toilet for a boat is a composting one! The smallest, most efficient composting toilet is an AIR HEAD.
The AIR HEAD toilet is a clever device. It keeps the urine separate from the solid matter. The urine can be easily disposed of in many ways - down a drain, in a public toilet even in a hole in the ground (with permission). The solid matter is composted in the unit and need only be emptied after several months to a year, depending on usage. There is a small fan (12 volt - 80mA) which draws air over the compost and ensures good drying and decomposing of the waste. Optionally, with the addition of a solar vent you can be completely independent of battery power.
We sold an initial batch of these in a few weeks and are now getting regular supplies as we are confident they will become the standard fitting on many boats.
Their popularity will be boosted by their small size, needing a space only 16" wide by 19" deep (40cm x 48cm). The unit stands 19" high (48cm). These toilets can be used in houses, motorhomes, caravans, horse-boxes, in fact anywhere that needs a toilet!
Contact us for more information or to discuss the benefits in more detail.