CM4310 Chemical Process Safety/Environment Fall 04 Homework #3 Solution Fri. 10 Dec., '04 1. Computer Project 5% of course grade: Take the Guided Tour in SimaPro6.0 Start SimaPro6.0 from the desktop using the Start icon on the lower right of the screen. Under CM apps, find the SimaPro6.0 icon. From the opening screen in SimaPro6.0 choose Introduction to SimaPro6 from the Projects window. Click Wizards on the left side top and select Guided Tour and then Guided Tour with Coffee. This tour illustrates concepts of LCA and capabilities of SimaPro 6.0 in the context of a life cycle study of a coffee maker. Go through both "Analyze a product" and "Analyze a product life cycle". Answer the question: which life cycle stage for a coffee maker has the most impact on the environment and why? Write a short summary of your discussion and reasons. How thorough you are will decide the grade for this project. Ans. The main life cycle stages of a coffee maker are 1. the production of the unit, 2. the use of it for making coffee (brews coffee twice per day, 365 days per year, for 5 years, use of electricity), 3. the use of filters (3650 filters), and 4. disposal of the unit in a landfill. The use of the coffee maker The stage with the highest impacts as judged by the single score in SimaPro6.0 is the use stage where electricity is consumed during brewing and keeping the pot warm ((9.2 pts). The next stage is the use of filters with 1.7 pts. Next is the disposal stage with 0.8 pts. Production stage for the coffee maker is only 0.75 pts. Finally, the packaging for the coffeemaker is the lease with 0.1 pts. 2. Comparison of Fluorescent versus Incandescent Light Bulbs Life Cycle Concepts and Abbreviated Analysis Fluorescent light bulbs provide similar lighting characteristics as incandescent bulbs, yet use just ¼ of the energy as incandescent bulbs. Their principles of operation account for this difference in efficiency. Incandescent bulbs operate by passing a current through a thin filament, which heats up until the filament glows and emits light. Thus, much energy is lost as heat. Fluorescent bulbs operate by passing a current through an ionizing gas, containing a mercury compound and a fluorescent compound. The gas does not heat up to nearly the same degree as the filament in the incandescent bulb, and therefore much less of the energy is lost. In this assignment you will apply basic elements of life cycle assessment, with a particular focus on energy and costs. Consider the following data for fluorescent and incandescent bulbs in answering the questions below. Fluorescent Bulb Incandescent Bulb
Light Output, (lumens) 1,700 1,690 Life (hr) 8,000 750 Energy Use Rate (Watt = 1 Joule/s) 26 100 Purchase Cost ($/bulb) 4.22 0.25 Energy Cost ($/kwh) 0.12 0.12 Disposal/Recycle Cost ($/bulb) 0.4 0.0 Data for light, life, and energy use rate from General Electric. Purchase cost based on Wal-Mart price. Energy cost is from Dr. Shonnard s UPPCO bill, Aug. 2004 Disposal / Recycle cost from Mike Kimmel, CheanLites Recycling, Inc., Mason, MI 48854 a. Before considering details of life cycle impacts, estimate the energy savings potential on a national scale of replacing all incandescent bulbs in home (residential) lighting applications with the new energy efficient fluorescent bulbs. Note, one pathway to sustainability involves using less energy to achieve the same societal benefit. In 2002, total US energy consumption was 97.4 quadrillion (10 15 ) BTUs (quad). Electricity in all applications consumes 39.6 quads of primary energy, and residential lighting is 3% of all electricity consumption in the U.S. Knowing that most residential lighting employs incandescent bulbs, to simplify this analysis we will assume that all energy consumption for residential lighting is due to incandescent bulbs. Now, assume that fluorescent bulbs replace all incandescent bulbs. Approximately how much energy can be saved each year in the U.S.? How large is this compared to annual U.S. energy consumption? State your answer on a percentage basis. data Annual USA energy consumption rate 9.74E+16 BTUs/yr data fraction of bulbs now incandescent 1 data electricity demand in USA 3.96E+16 BTUs/yr data fraction of electricity for residential lighting 0.03 data incandescent bulb usage rate 100 Watts data fluorescent bulb usage rate 26 Watts ans. incandescent bulb energy consumption 1.19E+15 BTUs/yr ans. fluorescent bulb energy consumption 3.09E+14BTUs/yr ans. energy saved by fluorescent bulbs 8.79E+14BTUs/yr ans. energy saved in percentage of USA annual rate 0.90 % b. Define functional unit and equivalence in this comparison of fluorescent and incandescent bulbs. How many incandescent bulbs are needed to equal one fluorescent bulb?
Functional Unit Definition: The comparison is based on bulb light output and lifetime of service. Both bulbs provide equivalent light output. The fluorescent bulb lasts 8,000 hours while the incandescent bulb lasts 750 hours. data light output of incandescent bulb 1690 lumens data light output of fluorescent bulb 1700 lumens data lifetime of incandescent bulb 750 hr data lifetime of fluorescent bulb 8000 hr ans. equivalence incandescent bulbs / fluorescent bulb 10.67 c. Develop an inventory of costs over the life cycle for each bulb type. Compare cost over the life cycle for fluorescent bulbs vs. incandescent bulbs. Which stage of the life cycle accounts for the greatest costs to the customer? The costs analysis includes three stages of the life cycle. First, the purchase cost is associated with the manufacture of the bulb, and includes the embedded costs for the manufacture of all materials in the bulb. The second cost is for the use of the bulb over the lifetime, 8,000 hours. The third cost is for recycle of the incandescent bulb. data cost of one fluorescent bulb 4.22 $ data cost of one incandescent bulb 0.25 $ data number of incandescent bulbs 10.67 data cost of electricity 0.12 $/kwhr data cost of recycle of one fluorescent bulb 0.4 $ data lifetime of bulb(s) operation 8000 hr data fluorescent bulb elec. usage rate 26 data incandescent bulb elec. usage rate 100 Fluorescent Incandescent ans. Purchase ($) 4.22 2.67 Use ($) 24.96 96.00 Recycle/Disposal ($) 0.40 Total ($) 29.58 98.67 The majority of the cost for either bulb over the life cycle is in the use of the bulb. d. Develop an inventory of energy consumption over the life cycle for each bulb type. For the bulb manufacture stage of the life cycle, use the following information for packaging and for inputs of materials for each product: (data taken from the life cycle assessment software tool SimaPro6.0 - it is on the network computers, so check it out.
One Fluorescent Bulb packaging: 4.5 g cardboard: Cardboard duplex/tripl: 1000 kg basis 0.117 MJ/bulb packaging: 33 g plastic - PP injection moulded: basis 1 kg 3.925 MJ/bulb bulb: 50 g white glass: Glass (white) B250: basis 1000 kg 0.604 MJ/bulb bulb: 40 g steel: ECCS steel 50% scrap: basis 1000 kg 1.013 MJ/bulb bulb: 10 g plastic: PP injection moulded: basis 1 kg 1.189 MJ/bulb One Incandescent Bulb packaging: 5.25 g cardboard Corr. Cardboard mix 1: 1000 kg basis bulb: 20 g white glass: Glass (white) B250: basis 1000 kg bulb: 10 g steel: ECCS steel 50% scrap: basis 1000 kg 0.171 MJ/bulb 0.242 MJ/bulb 0.253 MJ/bulb Note: MJ = megajoules, There are 3.6 MJ per kilowatt-hour (kwh). Finally, estimate product use stage energy consumption and remember to convert to primary energy using an efficiency of electricity generation of 35%. Organize your energy inventory results by life cycle stage in a neat table. Which stage accounts for the most energy consumption? Ans. One Fluorescent Bulb Total Energy per Fluorescent Bulb, Production 10.67 Incandescent Bulbs Total Energy per Incandescent Bulb, Production Total Energy 10.67 Incandescent Bulbs, Production 6.849 MJ 0.666 MJ/bulb 7.104 MJ The production stage calculation above includes all impacts from raw materials extraction from the environment up until the production of the bulb and out the factory gate. 10.67 Incandescent bulbs consume slightly more energy than fluorescent bulbs during the production stage of the life cycle, but the values are very close and likely within uncertainty. Energy consumed during bulb use data efficiency of electricity generation 35% data conversion of kwh to MJ 3.6 MJ/kWh data conversion of W to kwh 1000 W/kWh data incandescent bulb usage rate 100 Watts data fluorescent bulb usage rate 26 Watts data lifetime of fluorescent bulb 8000 hr Total Energy per Fluorescent Bulb, Use stage 2,139.4 MJ Total Energy 10.67 Incandescent Bulbs, Use stage 8,228.6 MJ Incandescent bulbs consume more energy during the use stage than one fluorescent bulb, by nearly a factor of 4.
Also, the Use stage of the life cycle consumes much more energy than the Production stage. The total energy consumed for Production and Use for both bulb types is Energy consumed during bulb Production and Use Fluorescent bulb 2,146.3 MJ Incandescent bulbs (10.67) 8,235.7 MJ The percent of energy consumed during Use is Fluorescent bulb = 2,139.4/2,146.3 x 100 99.68 % Incandescent bulbs (10.67) = 8,228.6/8,235.7 x 100 99.91 %