Question

# In evaluating the energy implications of the choice between reusable and single use cups, th eenergy required in heating wash water is a key parameter. Consider a comparison between single-use polypropylene (S.U.) and reusable polypropylene (R.U.) cups. The reusable cup has a mass of 45g, while the single use cup has a mass of 3.2 g, both of which require petroleum feed stocks to create. a.) Calculate the number of times the reusable cup must be used in order to recoup the energy in the petroleum required to make the reusable cup b.) Assuming that the reusable cup is washed after each use in 0.27 liters of water, and that the wash water is 80°C (heated from 20°C), calculate the energy used in each wash if the water is heated in a gas water heater with an 80% efficiency. Then, calculate the number of times each reusable cup must be used for the energy required to make the reusable cup and th energy used to heat the wash water to be equal to that of the disposable cup. Assume that1.2 kg of petroleum is required to produce 1 kg of polypropylene and that the energy of combustion of petroleum is 44 MJ/kg. The energy needed to wash cups is given as q MCAT, where c for water = 4.184 J/g K c.) Repeat part b.) assuming that an electric water heater is used (80% efficiency) and that electricity is generated from fuel at a 33% efficiency.  Fig: 1  Fig: 2  Fig: 3  Fig: 4  Fig: 5