A biological toilet, or composting toilet, isn't hooked up to sewer lines. The unit has a seat and a lid, but not a toilet bowl filled with water. How does it function? First, the waste is deposited into the unit in the normal way. After that, natural processes take over: ninety percent of the waste is water, which evaporates into the air. The toilet usually has fans and ventilation to assist in this process. The solid part of the waste then remains in a chamber, where it decomposes. Specialized bacteria digest the waste, given the right combination of oxygen, moisture, and heat. When the decomposition process is complete, the compost from the toilet can be removed and used in gardens and around trees.

Which organizational structure does this text primarily use?