Add pork spareribs and 8 cups water into a large pot. Bring to a boil over high heat. Skim the foam from the surface until the soup is clear.
While boiling the ribs, prepare the lotus root. Wash lotus root carefully. Peel the root and remove tough ends. Cut into 2 equal parts lengthwise, then chop into irregular bite size pieces.
(Optional) Transfer the ribs and boiling water into a dutch oven, without transferring the cooked blood on the bottom of the pot. This step helps you to get a clear soup in the end. You can skip this if you like.
Place lotus root into the dutch oven containing the ribs (If you skipped step 2, add the lotus root into the big pot with the ribs). Add Shaoxing wine, ginger, and green onion. Bring to a boil over high heat. Cover and cook over low heat for 1.5 to 2 hours, until the ribs almost fall off the bones and the lotus root becomes very tender. If the soup reduces too quickly, add a bit hot water during cooking. Do not add water during the final 30 minutes.
Add salt to taste.
Dipping sauce
Mix light soy sauce, black vinegar, and sugar in a small bowl.
Serve the soup warm with the dipping sauce. Dip the ribs in the sauce while eating.