Lugworms eat the sand on the tidal flats. They digest anything edible in the sand. The filtered sand is ejected after going through their intestines. In order to get enough to eat, the animal has to process a lot of sand. It eats 3.5 liters of sand per year. Lugworms live in a U-shaped tunnel. They eat sand from one end of the tunnel, forming a funnel on the surface. Whatever is indigestible is pressed out at the other end of the tunnel. This is where the typical spaghetti piles of sand come from.