Just like animal waste (manure) and food waste, human waste can be composted successfully and used as fertilizer. Sewage systems in many areas can't always handle the massive amounts of human waste and water supplies become contaminated. As beneficial as composting toilets are, they aren't without problems.
If your composting toilet is working properly, it should be odorless. An odor means that your toilet is not composting the way it is supposed to. Usually, this is because there is not enough dry material to support aerobic (with oxygen) decomposition. The decomposition process for liquid is anaerobic (without oxygen) and very smelly.
Excess liquid is the most common problem with a composting toilet. Some manufacturers may say not to urinate in a composting toilet, but that is beyond impractical. Adding dry material, such as sawdust, can help absorb excess liquid. The best permanent solution to this problem is to have a composting toilet that diverts liquid away from the solid waste.
Removing the Finished Compost
Sometimes, removing the finished compost can be a problem. This is usually due to the system being overloaded. Excess liquid can be the problem, making for a very messy removal. It is important to remove finished compost promptly. You can also help make the process easier by using a lightweight composting medium such as peat moss. Be aware that the most common commercially available composting toilets are only meant for seasonal use and won't be able to handle daily household use.