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Life Cycle Assessment of a Laptop Computer and its Contribution to Greenhouse Gas Emissions

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Mass production and extensive usage of personal computers such as desktops and laptops contribute to global warming. The demand for higher performance and faster processing capabilities make new models of laptop computers obsolete in a relatively short amount of time: the average lifespan of a laptop is typically between 3 to 4 years. In this paper, a life cycle assessment (LCA) is used to examine the full life cycle of a laptop computer from materials acquisition to manufacturing, use, and end-of-life disposition in terms of contribution to green house gas (GHG) emissions. From this analysis, the amount of GHG produced from the life cycle of a laptop computer is determined.
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Life Cycle Assessment of a Laptop Computer and its
Contribution to Greenhouse Gas Emissions
Anh Hoang, Weili Tseng, Shekar Viswanathan+ and Howard Evans
School of Engineering and Technology
National University
3678 Aero Court, San Diego 92123
ABSTRACT
Mass production and extensive usage of personal computers such as desktops and laptops
contribute to global warming. The demand for higher performance and faster processing
capabilities make new models of laptop computers obsolete in a relatively short amount
of time: the average lifespan of a laptop is typically between 3 to 4 years. In this paper, a
life cycle assessment (LCA) is used to examine the full life cycle of a laptop computer
from materials acquisition to manufacturing, use, and end-of-life disposition in terms of
contribution to green house gas (GHG) emissions. From this analysis, the amount of
GHG produced from the life cycle of a laptop computer is determined.
Introduction
Computers, printers, copiers, fax machines, VCRs, cell phones, and stereos are some of
the electronic devices that are most commonly associated with e-waste. Among this
group, computers are the biggest contributor to the amount of waste being generated
(William, 2004). When old computers become obsolete or lack the required functional
capabilities, they often end up in landfills or get shipped to third world countries, where
the wastes can become a major environmental and health concern (Carro, 2008).
+ Correspondence should be addressed to: sviswana@nu.edu
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A great amount of energy and resources is required to build a laptop computer. A
United Nations University study found that it requires around 1.8 tons of total raw
materials and other natural resources to manufacture an average desktop computer with a
monitor. According to the study, the production process of a desktop computer and a 17-
inch CRT monitor requires 240 kilograms of fossil fuels, 22 kilograms of chemicals, and
1,500 kilograms of water. This is equivalent to a mid-size vehicle (Williams, 2004).
Many of the components that require a great amount of energy during the manufacturing
process, such as semiconductors, are destroyed during the recycling process and are never
recovered. Hence, the author highly recommends that each user tries to upgrade his/her
computer to extend its useful life before sending it to the landfill or putting it up for
recycling (Williams, 2004). To fully understand the impact of a personal computer on
the environment, a detailed study of the life cycle stages of a computer is required. To
accomplish this task, a computer needs to be broken into functional units and each unit
must be analyzed separately in each of the life cycle stages.
Methodology
A study by the U.S Department of Energy estimated that the production and usage
of computers accounted for 2% of the total global greenhouse gas (GHG) emission in the
United States (Masanet et al., 2005). There are an estimated 3.95 million laptop
computers in California. In this study, the amount of GHG generated from the time of a
laptop’s manufacture through its disposal is assessed using life cycle analysis.
Analysis
The main board of a laptop computer includes a printed circuit board assembly
(PCB) and other small electrical parts such as resistors, condensers, and connectors.
3
Manufacturing these electrical parts within the main board is the predominant contributor
to global warming during the pre-manufacture stage because it is during this time frame
that much of the global green house gases are emitted. Substantial quantities of air
pollution, wastewater, and solid waste are emitted during this phase (Choi et al., 2006).
Based on the study by European Commission (2007), the energy used and CO2 equivalent
emission in the pre-manufacturing stage was found to be 1117.72 MJ, of which, 630.41
MJ was electricity energy. This is equivalent to a total emission of 71.15 kg of CO2 eq.
of GHG. Laptop manufacturing is a rather simple process; therefore, no major
environmental impact is observed at this stage. Laptop manufacturing involves assembly
and packaging. These activities require little electricity, and emit little air pollutants,
wastewater, and solid waste. Material extraction, production, manufacturing, and
distribution of a laptop computer are expected to consume about 1634 MJ of energy and
emit approximately 90.51 kg of CO2 eq. (European Commissions, 2007). To calculate the
total GHG emission contribution from the production of a laptop, the number of laptops
produced in the U.S. for this study was obtained from International Data Corporation
(Bell et al., 2008). Table 1 summarizes the total annual number of laptops produced and
annual amounts of energy consumed and GHG emitted.
Table 1: Total Laptop Production, Energy consumption, and GHG Emissions
(U.S., 2008-2012) (Bell et al., 2008)
Year
Laptop
Production Rate
Growth
(%) Over
Previous
Year
Energy
Consumption
GHG Emissions
MJ
Tons of CO2 eq.
"2008"
33,837,000
22.2
5.53E+10
3.06E+06
"2009"
39,048,000
15.4
6.38E+10
3.53E+06
4
"2010"
44,369,000
13.6
7.25E+10
4.02E+06
"2011"
49,439,000
11.4
8.08E+10
4.47E+06
"2012"
52,771,000
6.7
8.62E+10
4.78E+06
The amount of electricity consumed in the product use stage depends on a variety
of factors. The maximum energy output for a laptop computer ranges anywhere from 50
watts to 100 watts (Samwell, 2004). However, a typical laptop rarely reaches its
maximum power capacity. The amount of energy consumed by a laptop depends on both
the type of applications running and on its operational mode. In this project, the
operational mode of the central unit and the monitor is treated as a single unit. The
modes used to estimate the power consumption are ACTIVE (average), SLEEP (average)
and OFF (average). The average power consumption for each operational mode and the
annual power consumption are shown in Table 2.
TABLE 2: Laptop Adjusted Power Consumption and Annual Power Consumption
(European Commission’s Report, 2007)
Electricity
Used
(kWh)
Power Consumed
Per Year (kWh)
Active (Average)
0.032
83.62
Sleep (Average)
0.003
8.99
Off (Average)
0.0015
4.73
TOTAL
97.34
The CO2 conversion factors provided by the California Department of Energy are
used to convert energy consumption (in kWh) into CO2 emissions (in kg CO2 equivalent)
(Price et al., 2002). To get kg of CO2 equivalent, the energy used was first multiplied by
the Carbon factor (0.108 kg C/kWh). The result was then multiplied by 1 kg of CO2/0.27
kg of C to get kg of CO2 emission equivalent (1 kg of CO2 = 0.27 kg of C). Based on this
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conversion, a laptop that consumes 97.34 kWh per year (Table 2) experiences annual
GHG emissions of 38.94 kg of CO2 eq.
Table 3 summarizes the projected growth for U.S. residential laptops from 2008
to 2012. The data on total PCs in Table 3 were derived based on the U.S. projected
population growth from the U.S Census Bureau and estimated PC penetrations in the U.S.
from the U.S Department of Energy (Horvath et al., 2007). Furthermore, an average of
2.59 persons per U.S. household and the U.S. residential PC penetration was 1 PC per
household was assumed (Horvath et al., 2007).
TABLE 3: U.S population and laptop projections (U.S., 2008-2012)
Year
Population
Projections
In millions
No. of
Household
In 1000s
Total Base
PCs
In 1000s
Total
Base
Laptops
(25% of
all PCs)
In 1000s
New
Laptops
18%
In 1000s
New
Laptops
(Pop.
Growth)
Obsolete
Laptops
In 1000s
Total
Laptops
In 1000s
2008
303.598
117,219
117,219
29,304
5,275
259170
5,346
29,492
2009
306.272
118,251
118,251
29,562
5,321
258108
5,395
29,747
2010
308.936
119,280
119,280
29,820
5,368
257143
5,443
30,002
2011
311.601
120,309
120,309
30,077
5,414
257239
5,488
30,260
2012
314.281
121,344
121,344
30,336
5,460
258678
5,534
30,521
The end-of-life of a laptop computer occurs when it no longer meets consumer
requirements or when it simply ceases to function properly. Laptop computers are
usually not replaced because they are worn out or broken, but rather because of an
increase in consumer demands for functionality, demands that are often triggered by the
introduction of new versions of software. The end-of-life is extremely difficult to
analyze due to the fact that not all recyclable parts of laptop computers are recycled.
Often, the recyclable materials are dumped in landfills (Masanet et al., 2005).
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To estimate the primary energy and GHG emissions associated with non-recycled
laptops, the following assumptions are used (Masanet et al., 2005):
1. 92% of obsolete laptops ended up in landfills, 8% get recycled.
2. An average laptop mass of 2.52 kg.
3. An average diesel fuel consumption rate for solid waste collection of 9.1 liters/ton.
4. An average diesel fuel consumption rate for landfill equipment of 5.8 liters/ton.
5. An average energetic value of 40 MJ/liter for diesel fuel.
6. A conversion factor of 3 kg CO2 eq/liter for diesel fuel combustion
This study calculated the total annual energy consumption and GHG emissions
associated with all laptop computer activities. As expected, data analysis showed that the
laptop production and use phases consumed the most energy and emitted the most
greenhouse gas. Energy consumption and GHG emissions for the end-of-life phase were
relatively low compared to other phases. Laptop production and usage accounted for
more than 99% of energy consumptions and greenhouse gas emissions. The total annual
energy consumption and GHG emissions are summarized in Table 4.
TABLE 4 Total Energy Consumption from Laptop Computers (U.S., 2008-2012)
Total Energy Consumption
2008
2009
2010
2011
2012
(MJ)
(MJ)
(MJ)
(MJ)
(MJ)
Production & Manufacturing
5.5300E+10
6.3800E+10
7.2500E+10
8.0800E+10
8.6200E+10
Use Phase
1.0300E+10
1.0400E+10
1.0500E+10
1.0600E+10
1.0700E+10
End-of-life (landfill)
7.3900E+06
7.4600E+06
7.5200E+06
7.5800E+06
7.6500E+06
Recycled (Credit)
8.5500E+06
8.6300E+06
8.7400E+06
8.7800E+06
8.8500E+06
Total
6.5599E+10
7.4199E+10
8.2999E+10
9.1399E+10
9.6899E+10
Based on data analysis for the year 2008 above, laptop computer activities in the
U.S. accounted for a total of 6.5599 x 107 gigajoules (GJ) of energy and 4.210 x 106 tons
of CO2 eq. emissions per year. Currently, California uses 9.54 x 108 GJ of electricity per
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year. The amount of energy consumed by laptop activities corresponded to 7% of total
annual electricity used by California. This is a significant number considering that
California is the most populated state in the U.S. The amount of annual GHG emissions
mentioned above is equivalent to the annual GHG emissions of 700,000 midsize vehicles
or to a single coal fired power plant (“Greenhouse Gas Equivalencies Calculator”, 2008).
Conclusions and Recommendations
This study showed that laptop production and usage still pose a significant threat
to the environment and to the sustainability of natural resources. Based on the study,
some of the specific tasks that can be implemented to reduce energy consumption during
the product use stage include the following:
Turning off computer when not in use
Setting up power management software to minimize energy use
Buying laptop computers with Energy Star label
Requiring the enabling of power management before shipping the product
Educating consumers to understand and use power management in a proper way, and
also offer guidance in purchasing choices
Another factor that can help reduce the amount of energy used during the product
use phase is implementing the installation of multi core processors. A multi core
processor can perform several tasks simultaneously instead of performing one task after
the other. Hence, the operational time for the laptop will be lower, thus forcing it to
consume less energy.
The production phase of a laptop is also energy intensive which indicates that the
production of the motherboard and battery manufacturing are relevant areas to target for
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improvement. It is estimated that only a small percentage of laptops is sent to recycling
centers, while the remainder ends up in landfills or is stored away. To encourage
recycling practice, it is recommended that cities set up multiple recycling centers by
enacting regulations. Another possibility is to make manufacturers responsible for end-
of-life collections and recycling. The United States can implement a regulation similar to
that implemented by the European Union so that obsolete computers and other electronic
goods do not end up in landfills.
References
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Ditch in Ghana. National Geographic. January 2008, p. 64-86.
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and its Effective Recycling Rate. Korean Computer Industry. Ecome Publishers.
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Computer Monitors. Retrieved July 2008 from http://www.ecocomputer.org.
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Energy Consumption and Greenhouse Gas Emissions of California’s Personal
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from www.linuxjournal.com/article/7539
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University. Environmental Science Technology, Volume 38. Tokyo, Japan.
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High Tech Trash: Will Your Discarded TV or Computer End Up in a Ditch in Ghana
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Carro C. (2008). High Tech Trash: Will Your Discarded TV or Computer End Up in a Ditch in Ghana. National Geographic. January 2008, p. 64-86.
An Analysis of Measures to Reduce the Life-Cycle Energy Consumption and Greenhouse Gas Emissions of California's Personal Computers. California Energy Institute Optimization of Product Life Cycles to Reduce Greenhouse Gas Emissions in California Extending Battery Life with Laptop Mode
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Personal Computers (Desktops and Laptops) and Computer Monitors
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Optimization of Product Life Cycles to Reduce Greenhouse Gas Emissions in California
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