Biodegradable soap contains ingredients that can be naturally broken down by bacteria in the soil. Soaps can generally be labeled as biodegradable if more than 90 percent of their ingredients break down in soil within six months.
Most soaps contain chemicals such as triclorocarban and triclosan that do not easily break down and can cause harmful damage to the environment. The chemicals eventually enter water sources, where they are nearly impossible to filter out. Phosphates are another harmful groups of chemicals found in many non-biodegradable soaps. These chemicals basically act as fertilizer, causing large algae blooms that take up the oxygen from the water and suffocate the other plants and animals.
While the chemicals in biodegradable soaps can be broken down in soil and thus usually don't leach into water sources, they do not break down if disposed of in a water source. The breakdown process requires the bacteria in the soil to destroy the soap chemicals. For this reason, all biodegradable soaps should be used sparingly and disposed of by burying it in a hole at least 200 feet from the nearest water source. Do not use biodegradable soaps directly in the water, such as bathing when hiking or camping.