there are provided to a biodegradable composition containing ground cellulose having a diameter of 300 μm to 1 nm , pulp , and water , a manufacturing method for the same , and a water - proof agent and a molded product using the composition . a molded product manufactured using the biodegradable composition of the present invention has a waterproofing function and an excellent strength for a certain period of time , and when the molded product is discarded , it is biodegraded without damage to the natural environment .