This is the CTS-2000. It is a vacuum toilet. Waste is vacuumed away with a little water, much like a flush toilet at home, and sent through a tube for processing. One advantage is that the tube can be 100 feet long, so the processing can be done far away from you, which is an advantage.
In this case, the waste-handling process is incineration. The blue box in this picture is a propane-powered combustion unit.
It's an interesting device, but it's overkill for a little summer house. The cost is high; 55,000 kronor! And then there's the matter of a big 'ol propane-powered poop processor just outside your home.