A waste disposer comprising a primary dehydrating chamber, a grinding device, a secondary dehydrating chamber, and a storage chamber. The primary dehydrating chamber is adapted to allow waste to be heated therein to partly dehydrate the waste. The primary dehydrating chamber has: a first waste inlet for receiving the waste, a first vapor outlet for exhausting vapor from the waste, a drainage outlet for draining free liquid from the waste, and a first waste outlet for outputting the partly dehydrated waste. The grinding device is adapted to receive the waste from the first waste outlet and grind the waste to reduce the size thereof. The secondary dehydrating chamber is adapted to allow the ground waste to be heated therein to further dehydrate the waste. The secondary dehydrating chamber has a second waste inlet for receiving the ground waste, a second vapor outlet for exhausting vapor from the waste, and a second waste outlet for outputting the further dehydrated waste. The storage chamber is adapted to receive the waste from the second waste outlet and store the waste in the storage chamber.