If reliable electricity is not an option, the BTS 33 is the way to go. Using a process known as batch composting, the BTS 33 can handle a high volume of usage. Batch composting is a process where you collect a batch of material and then remove it from service so the material can compost without anything new being added to it.
The BTS 33 comes with the same advanced ventilation system as described in previous models, but it works by applying a very different approach. Using the batch compost method, alternating bins are used to compost the material. One bin is placed in the toilet until it becomes 3/4 full, then it is removed outside for further composting and the alternative bin is placed in the unit in order to continue its operation.
Air circulation through the unit occurs due to the natural convection of air through the ventilation pipe. This is induced by the heat that is produced by the composting process, temperature differentials between the inside and outside of the structure, and by the natural chimney effect created by the vent pipe. Installing an optional 12V DC fan into the vent pipe can induce additional circulation of air and increase the capacity of the unit.