20th CIRP International Conference on Life Cycle Engineering, Singapore, 2013. Life Cycle Assessment: A Comparison of Manufacturing and Remanufacturing.
Life Cycle Assessment: A Comparison of Manufacturing and Remanufacturing Processes of a Diesel Engine 1
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Avilon Sebastiao Dias , Hoyeol Kim , Pradeep Kumar Sivakumar , Zhi-Chao Liu , and Hong-Chao Zhang 1 2
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Texas Tech University, Lubbock, Texas, USA
Dalian University of Technology, Dalian, Liaoning, China
Abstract The purpose of this study is to compare the environmental impacts and energy consumption of a newly manufactured and a remanufactured diesel engine with respect to the processes involved in manufacturing of a new diesel engine as well as remanufacturing of a used diesel engine. The result of the study shows that a remanufactured diesel engine is better than a newly manufactured one in terms of the amount of energy consumed in the process of manufacture and the environmental impacts resulting from the life cycle of the manufacturing and remanufacturing processes. Keywords: LCA; Remanufacturing; Diesel Engine 1
INTRODUCTION
According to the Bureau of Transportation Statistics (BTS) the total energy consumption of 28.927 quadrillion BTU in 2007 we have transportation consuming over 22.3 quadrillion BTU per year [1]. This consumption of energy is inevitable as this sector including the heavy trucks and trailer trucks are the backbone of the economy, transporting millions of tons of goods across the country. Over the years we have seen a steep rise in the total consumption of energy and we have had almost a rise of over 1% per year in ten years [1]. The major reason for these vehicles having such a large contribution of energy is due to their extensive driving cycles and also their low fuel economy. It is being realized that the largest component which leads to the most amount of energy consumption in the vehicles is the engine of the vehicle. Thus we have included in this investigation the potential of reusing and remanufacturing the engine of the vehicle.
Figure 1: Energy consumption for the US manufacturing subsectors.
Today when an engine has reached the end of its life we have three options which include landfill, recycling the entire engine where only the materials of the engine is recovered, or remanufacturing the engine and selling it like a new engine which can go on to another life cycle. If recycled, the entire processes such as molding, casting, machining, etc. can be conserved in the process of remanufacturing. According to the Production Engine Remanufacturers Association (PERA), remanufactured engines contribute to almost 2.5 billion dollars which encompasses over 2.4 million engines remanufactured every year [2].
Having little research present on the remanufacturing energy consumption and the energy savings as well as emissions savings that it produces over the manufacturing, this study presents an extensive approach to comparison between the manufacturing and remanufacturing of a large diesel engine to analyze the potential that remanufacturing has in terms of energy savings and reduction in emissions.
In this study we have considered the total energy consumption and the environmental impact of manufacturing as well remanufacturing a heavy duty 6 cylinder truck engines and in doing so we have compared the amount of energy saved and the benefits obtained.
The data from SINOTRUK , commercial truck manufacturing company, was used for the study. The diesel engine under consideration was a 6 cylinders, in-line, water cooled and turbocharged engine. The scope of the analysis includes:
To begin with we quantify the energy consumption of manufacturing and remanufacturing of the engine. In the manufacturing sector itself we have witnessed a large influx of emissions as well as indirect emissions through the use of electricity. The breakdown of the energy consumptions in the United States in the manufacturing subsectors is shown in Figure 1 [3].
The quantification of energy consumption and emissions directly related to the manufacturing of the engine.
The quantification of energy consumption and emissions directly related to the remanufacturing of the engine.
A quantitative comparison between the two processes so as to provide a holistic picture of the benefits of the remanufacturing over that of manufacturing a new diesel engine.
The parts of the remanufactured engine are considered to be of the same quality as that of a newly manufactured one.
In the avenue of remanufacturing we consider the major sub events that would include disassembling, cleaning, refurbishing and reassembling of the parts so as to create a product which is almost like a new one.
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SCOPE OF STUDY TM
20th CIRP International Conference on Life Cycle Engineering, Singapore, 2013
676
2.1
A.S. Dias et al. The focus of the study is on the processes of manufacturing and remanufacturing, but the time of use of the car is not considered in the scope of the study. Functional Unit
The functional unit considered in this study is the production processes of manufacturing and remanufacturing of a diesel engine. 2.2
Manufacturing
Remanufacturing
Energy savings
% Reduction
6,016.68
3,620.16
2,396.52
39.83%
Energy consumption (MJ)
Table 1: Comparison of energy consumption.
System Boundary
Manufacturing In the manufacturing process we consider the entire processes of manufacturing which include raw materials extraction, parts production, and parts assembly as well as the transportation of parts between the production plants. The flow chart of the manufacturing processes is shown in Figure 2.
Resource Coal (kg) Crude oil (kg) Natural 3 gas (m )
Remanufacturing
% Reduction
2,200.00
590.00
73.18%
59.50
48.50
18.49%
17.00
5.23
69.24%
Manufacturing
Table 2: Comparison of resources consumption. 3.4
Figure 2: Flow chart of the manufacturing process.
Environmental Emissions Analysis
Remanufacturing resulted in significant reductions in air emissions as well as water emissions. The production of a new diesel engine produces 3.90 tons of carbon dioxide emissions. The production of a remanufactured diesel engine, on the other hand, produces 1.02 tons of CO2 emissions. Overall carbon dioxide emissions were reduced by 73.88%. The remanufacturing of a diesel engine offered CO reductions of 22.83%, SO2 reductions of 70.80%, etc (Table 3).
Remanufacturing
Pollutant
In the remanufacturing process we consider disassembly of parts, parts cleaning, refurbishing and repairing of parts, finishing of parts, and final assembly. The flow chart of the remanufacturing processes is shown in Figure 3.
Air emissions (kg)
Figure 3: Flow chart of the remanufacturing process. 3 3.1
LIFE CYCLE INVENTORY (LCI) Energy Consumption Analysis
The energy consumption for a new and remanufactured diesel engine was compared. The production of a new diesel engine required 6,016.68 MJ of energy, 1.66 times more than that of a remanufactured engine, which required 3,620.16 MJ. Thus, the use of a remanufactured diesel engine can potentially avoid the extra 2,396.52 MJ of energy that would be required to create a new one. As a result, there were about 40% savings for the remanufacturing of a diesel engine (Table 1). 3.2
Natural Resources Consumption Analysis
There are 3 kinds of natural resources used in the production of a new and remanufactured diesel engine. Remanufacturing offers significant savings in every natural resources consumption category with a range in reductions of 18.49% to 73.18% (Table 2).
Water emissions (kg)
Manufacturing
Remanufacturing
% Reduction
CO
0.89
0.68
22.83%
CO2 (t)
3.90
1.02
73.88%
SO2
11.52
3.36
70.80%
NOx
8.13
3.11
61.79%
CH4
5.90
4.10
30.65%
H2S
0.03
4.48E-04
98.21%
HCL
0.65
0.26
59.68%
CFCs
2.92E-06
7.26E-07
75.15%
COD
5.02
0.40
92.03%
NH4
0.03
0.01
74.07%
Table 3: Comparison of environmental emissions. 3.5
Effects of Remanufacturing
A comparison of the LCI of a new and remanufactured diesel engine shows that remanufacturing provides significant reductions in energy and natural resources consumption, and environmental emissions (air and water). A remanufactured engine requires fewer new parts and less manufacturing than a new engine and is more labor intensive rather than energy intensive. As a result, it can be produced with 39.83% less energy and reduces natural resources consumption by 18.49% to 73.18%. Carbon dioxide emissions were reduced by 73.88%. All other air emissions showed significant savings as well, with a range from 22.83% to 98.21%, and savings in water emissions were between 74.07% and 92.03%.
Life Cycle Assessment: A Comparison of Manufacturing and Remanufacturing Processes of a Diesel Engine In summation, diesel engine remanufacturing offers environmental benefits in the form of increased material productivity and environmental savings. 4 4.1
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this phase of the life cycle contributes to 95% to ozone layer depletion, 89% to climate change, 86% to acidification, 84.7% to respiratory effects (inorganic), 82.3% to respiratory effects (organic), and 65.5% to fossil fuels.
LIFE CYCLE IMPACT ASSESSMENT Methodology and Assessment Model
The Eco-indicator 99, damage oriented method for LCIA, is employed to assess the environmental impact. The main impact categories to be investigated under this study are: respiratory effects, climate change, ozone layer depletion, acidification, and fossil fuels. At each process in manufacturing and remanufacturing, inventory data sets including resources extraction and air/water emissions were collected and classified into the impact categories. Through characterization, the environmental impacts were calculated at each category. Lastly, we investigated which process has the most significant impact on the environmental damage in manufacturing and remanufacturing, respectively. Also, we directly compared the impact of manufacturing with that of remanufacturing on the damages. 4.2
Figure 5: Environmental impacts of remanufacturing.
Environmental Impacts of Manufacturing
Based on the results of characterization, impact indicators at each process were converted into the ratio value to the total within each impact category. An overview of the relative contribution of the different stages of manufacturing to the different impact categories is presented (Figure 4). The stage of raw material mining and production of a diesel engine plays an important role in the total environmental impacts. This process contributes more than 99 % to the most impact categories: respiratory effects (organic), climate change, and fossil fuels. It consumes a lot of fossil fuels such as coal, gas, and oil, and produces a lot of CO2 which influence climate change, and CH4 which affect respiratory effects (organic). On the other hand, materials transportation yields only an insignificant contribution to all the impact categories considered in this study.
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The Comparison: Manufacturing vs. Remanufacturing
In order to compare directly environmental impacts of manufacturing and remanufacturing, firstly, impact indicators within each impact category across each process were summed up by manufacturing and remanufacturing, respectively. Next, the results for each impact category have been normalized to the largest total impact. The environmental impacts of manufacturing and remanufacturing were compared for different impact categories and presented in a diagram (Figure 6). The highest contribution to a particular impact category is indicated with a 100 % bar. The following figure shows the damage assessment results. Comparing the life cycle stages of the manufacturing and remanufacturing, it is remarkable that all of impact categories such as respiratory effects, climate change, ozone layer depletion, acidification, and fossil fuels have the greatest contribution to the overall environmental impacts by manufacturing of a diesel engine. In other words, remanufacturing of a diesel engine has lesser contribution to the environmental impacts when compared to manufacturing of a diesel engine.
Figure 4: Environmental impacts of manufacturing. 4.3
Environmental Impacts of Remanufacturing
The relative contribution of remanufacturing a diesel engine to the total environmental impacts is presented (Figure 5). It can clearly be seen that the components remanufacturing of a diesel engine significantly contributes to all of impact categories. More specifically,
Figure 6: Comparison of manufacturing and remanufacturing.
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A.S. Dias et al. CONCLUSION
From the analysis conducted above it is quite evident remanufacturing process is better than the manufacturing of the amount of energy consumed in the process environmental impacts resulting from the life cycle manufacturing and remanufacturing processes.
that the in terms and the of the
This study can be further expanded to consider the use phases of both a newly manufactured engine and a remanufactured engine. The major impact from an engine could be realized during the use phases of the engine. The consumption of fuel and lubricants would be quantified based on an assumption that the new engine travels for 192,000km in 15 years during its lifetime and consumes 10L for every 100km. The same approach can been used for a remanufactured engine but in the remanufactured engine there has been a lot of conflicts with data procurement as the remanufacturing companies challenge that their engines work at the same standards as a new engine, but some customers using these engines do not agree to the assertion made by the remanufacturing companies. Hence this problem can be solved by means of considering a ‘sample space’ of a certain number of trucks, and the operation of these trucks can be monitored so as to give more quantitative results thus resulting in a more holistic comparison between the two engines by including the use phases in which they are being used.
This will lead to develop a more quantified study which will actually convey on whether it is economical as well as environmentally feasible to use a remanufactured engine as compared to a newly manufactured engine. 6
REFERENCES
[1]
Davis, S.C., Diegel, S.W., Boundry, R.G. (2009): Transportation Energy Data Book Edition 28. Prepared by The Oakridge National Laboratory for the US Department of Energy.
[2]
Smith, V.M., Keoleian, G.A. (2004): The Value of Remanufactured Engines: Life-cycle Environmental and Economic Perspectives, Journal of Industrial Ecology. Vol. 8, No. 1-2, pp. 193-221.
[3]
U.S. Energy Information Administration (2007): 2002 Energy Consumption by Manufacturers.
