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Assignment 2 – LCA Exercises
Problems
1. Choose one product and construct a materials and energy flow diagram, with minimal detail in the pre-manufacturing and manufacturing stages and enhanced detail in the product delivery and use stage. Suggest appropriate actions by the design engineer.
2. Compare the use of virgin paper and recycled paper. Compare from an environmental point of view the use of recycled paper and the use of paper obtained from paper pulp. The recycled paper has been obtained from paper wastes transported in 16-t trucks from a distance of 1000 km. The total emissions of carbon dioxide, CO2, and the generated solids in kg of them are used as comparison parameters. It is desirable to compare the derived effects of the following two scenarios:
• purchasing a 400-g pack of new writing paper at the corner stationery shop • driving to buy a similar pack of recycled paper at an establishment 1 km away.
Only the ELs due to raw materials and transportation are considered. Use the following environmental loads:
EL/kg of recycled EL/kg of pulp
EL paper paper EL/km (car) EL/tkm f 16-t truck)
kgCO2 1.03 1.61 2.16 x 10-1
kg solids 7.06 x 10-2 1.73 x 10-1 7.50 x 10-6 3.46 x 10-1 7.19 x 10-2
tkm is equivalent to a mass of 1 t (1000 kg) transported 1 km.
3. Compare the use of paper towels and an air dryer to drying the hands. Compare environmentally the use of paper towels for drying hands and the use of a hand-dryer supplied with electricity from a gas thermal power plant or from an eolic power plant. The considered comparison parameters are the emissions of carbon dioxide, CO2, and sulfur dioxide, SO2.
Suppose that the weight of a paper towel is 7 g and that the electric hand-dryer is 2000 W and works for 30 s. With these data, determine the best way, from an environmental point of view, to dry the hands. The ELs related to the paper and the use of electricity are assumed to be the following:
Electricity consumption: Ec (kWh); Ec = (2000 (J/s)/1000)(30/3600) = 1.67 X 10-2 kWh.