In many places in California, earthworms are used to clean the polluted mud at the end of sewer systems. Tainted land which has passed through the earthworm becomes revitalized soil, and can be sold and used. Reducing garbage can thus be profitable for people.
加州許多地方就利用蚯蚓清理衛生下水道的汙泥，經蚯蚓「生活」過的汙泥，成為「再生土」，再出售利用，垃圾因此減量，也為人們帶來利潤。