Every year millions of gallons of water are used to flush American toilets. Most of that water ends up in a waste treatment plant where megawatts of energy (most created by coal/oil/gas) are used to process out the waste, or in a septic system. Septic systems are one of the main cause of eutrophication often leak and cause pollution and are far from a perfect solution to waste water.
In the U.S., approximately 40 percent of all domestic water consumed is flushed down the toilet. One person using an older 5.5 gallon flush toilet will use 13,000 gallons of fresh water per year to dispose of 165 gallons of body waste. New toilets have since moved to 1.6 gallons per flush, but as you can see this is still a large amount of waste water for such a small amount of waste.
What if there was a way to avoid all this wasted water, and wasted energy, while cutting down on the amount of nutrient pollution we put into the world? Just so happens that we already have a way. Say hello to the composting toilet.