Consider a privately owned retail business that sells metal accessories. The business receives approximately 250 lbs of new merchandise every day. Since much of the merchandise sold must be matched to an old sample for verification, most customers bring their old merchandise into the store. Several customers leave their old parts behind to be disposed by the business. It is estimated that about 20 percent of the total amount of metal sold is brought in and left by customers. 

            Of the amount of total merchandise received, approximately 9 percent of the weight is in packaging material (paper and cardboard). Eighty-seven percent of the packaging material is cardboard, of which 60 percent is recycled after the merchandise is unpacked. About 7 percent of the paper and 15 percent of the cardboard is sold with merchandise over the counter. The remaining paper and cardboard is disposed by in the dumpster. 

            The remaining weight of merchandise is metal parts and chemicals. Chemicals make up 11 percent of the total and all but 10 percent are sold daily. The remaining 10 percent is used within the business for cleaning equipment and is disposed of as hazardous waste. Seventy-eight percent of the metal parts are sold per day with the remainder stored internally. Perform a mass balance and a flow diagram. 

 

2. Consider a household that generates a certain amount of waste per day. Of this amount, bottles and cans represent 20 percent (by weight) and are recycled by the family. Twenty percent of the paper waste (32 percent total) is burned in the fireplace. The remaining paper along with the rest of the waste is put into containers for collection. On a given day, 20 lb of consumer goods (food, newspapers, magazines, etc.) are bought into the house. The family consumes 7 lb of food that day, and 5 lb of food is stored. The magazine received represent 5 percent of the paper waste of the day, and they are not thrown away. Draw a materials flow diagram of this problem and calculate the amount of solid wastes disposed of during this day.