Life Cycle Environmental Impact Evaluation of Newly Manufactured Diesel Engine and Remanufactured LNG Engine

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ScienceDirect Procedia CIRP 29 (2015) 402 – 407

The 22nd CIRP conference on Life Cycle Engineering

Life Cycle Environmental Impact Evaluation of Newly Manufactured Diesel Engine and Remanufactured LNG Engine Junli Shia,b,*, Tao Lia, Zhichao Liua, Hongchao Zhanga,c, Shitong Penga, Qiuhong Jianga, Jinsong Yind a

Dalian University of Technology, Dalian 116023, China b

Dalian Polytechnic University, Dalian 116034, China

c

Texas Tech University, Lubbock, TX 79409-3061, USA

d

Zhangjiagang Furui Special Equipment CO., LTD, Zhangjiagang 215637, China

* Corresponding author. Tel.: +86 15504949305; fax: +0-000-000-0000. E-mail address: [email protected]

Abstract The application of Liquefied Natural Gas (LNG) in vehicles is considered to be an important way to solve the energy and environmental problems. In China, many waste diesel engines are beginning to be remanufactured to LNG engines. In this study, a life cycle assessment is carried out to quantify the energy saving and environmental emission of a remanufactured LNG engine and newly manufactured diesel engine, both engines are compared by means of material usage, cumulative energy requirements and environmental emissions over the entire life. The results show that, compared with diesel engine newly manufacturing, LNG engine remanufacturing could reduce 42.62% of primary energy demand (PED); the environmental impacts reduction of acidification potential (AP) and nutrient enrichment potential (EP) could reach to 69.61% and 71.34%, which are most distinct; global warming potential (GWP) and photochemical ozone formation potential (POCP) can be reduced by 46.42% and 43.90% respectively. Keywords: Life cycle assessment(LCA); remanufacturing; liquefied natural gas (LNG); diesel engine; environmental impact

1. Introduction China is one of largest energy and resource consumption country in the world. Considering the immense environment pollution and large resource consumption [1], automobile industries can not shirk their responsibilities. By 2014, there more than 140 million vehicles in China; manufacturing and driving of the automobile consume a lot of metal, oil and other mineral resources. The oil consumption of the automotive industry has outstripped 1/3 of the total consumption. As for the air pollution, automobile exhaust contributes 38.5% of CO, 11.7% of CO2, 87.6% NOx and 6.2% of SO2. In addition, scrapped automobiles not only produce a lot of waste, but also occupy land resources. Face with these serious environmental problems, government and automobile manufacturers are exploring ways to minimize the effects of the activities on environment by providing “greener” products and using “greener”

processes. Remanufacturing, as the ultimate form of recycling, is an excellent production mode [2], which could restore the used products of high value-added into like-new condition to get great benefits of energy saving and emission reduction, in addition to the economic benefits [3,4]. Due to its significant effects on energy saving and emission reduction, automotive components remanufacturing has become an important direction for industry sustainable development [5,6]. In China, more and more waste diesel engine of automobile are being remanufactured to Liquefied natural gas (LNG) engine. Former researchers have studied the environmental gains from remanufacturing on the automotive industry or devices [7,8,9]. Liu et al. [10] have studied the environmental benefits of remanufactured diesel engine compared to newly manufactured diesel engine. Moreover, there are also researches about the fuel benefit of LNG vehicles; studies suggested that the use of LNG vehicles could reduce much energy consumption, CO emissions, and CO2 emissions

2212-8271 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of The 22nd CIRP conference on Life Cycle Engineering doi:10.1016/j.procir.2015.01.029

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compared with the diesel counterpart [11, 12]. The previous studies are mostly focused on the economic and environmental benefit of remanufacturing in automotive (or engine), or fuel advantages of LNG compared to diesel. However, there are few studies about the environmental benefit of remanufactured LNG engine compared with newly manufactured diesel engine. This LCA study intend to evaluate the environmental benefits of remanufactured LNG engine compared with newly manufactured diesel engine and identify the largest negative impact on the environment during the whole life cycle of the two engines.

2.3. Methods and database Life Cycle Assessment (LCA) methodology would be applied in this study. LCA is a “cradle-to-grave” approach for assessing industrial systems, which enables the estimation of the cumulative environmental impacts resulting from all stages in the product life cycle [13]. The data related to energy requirements, air/water emissions are referred from the CLCD (Chinese Life Cycle Database). CLCD is a Chinese local life cycle database developed by IKE Environmental Technology and Sichuan University, which is on behalf of China market average industrial level [14].

2. Goal and scope definition 3. Life cycle inventory analysis 2.1. Goal and scope 3.1. Materials for newly manufacturing /remanufacturing Engines is the key component of automobile, automobile manufacturers treat engine as the competition highlight, and pay more attention to energy consumption, exhaust emissions and environmental protection. The goal of this LCA study is to evaluate and compare the energy consumption and environmental impacts of two kinds of engines: a newly manufactured diesel engine and a remanufactured LNG (Liquefied Natural Gas) engine. The engine under this LCA study is SINOTRUCK WD615.68, with six in-line cylinders, maximum output power of 250 kW, and a total displacement of 9.726 liters. We define the total driving distance is 300,000 kilometers (km), which is the average lifetime of this type of engine. 2.2. LCA system boundary The system boundary of this LCA is shown in Fig. 1. The life cycle of the two engine include: raw/additional material production, materials transport/old diesel reverse logistics, components manufacturing/remanufacturing, engine transport, diesel/ LNG engine usage and old engine recycling.

The materials consumed in engine newly manufacturing are mainly steel, cast iron, aluminum and Al-Si alloy. As for the LNG engine remanufacturing, there are some additional materials, such as, cast iron, copper and rubber, which used to modify and refurnish the engine; diesel as well as kerosene are the main cleaning materials during component cleaning process. The respective quantities of the main materials used in manufacturing/remanufacturing are shown in Table 1. Table 1. Main materials used in manufacturing/remanufacturing. Materials for manufacturing Steel Cast Iron Aluminum Alloy



Quantity(kg) 195.05 584.64 41.23 35.32



Materials for remanufacturing Cast Iron Aluminum Copper rubber Diesel Kerosene

Quantity (kg) 37.37 28.01 3.05 7.50 16.5 10.3

3.2. Materials transport / old diesel engine reverse logistics Shanghai Baosteel is the materials provider of steel and cast iron for SINOTRUK. The materials are transported by truck (carrying capacity: 10t, truck consumes gasoline only), and the distance is 800 km. The other materials transport was not taken into consideration due to the small quantity. Old diesel engines are recycled back from 4S shops by truck (carrying capacity: 50t consumes diesel only), the average distance is estimated to be 720 km. The corresponding transportation unit in CLCD can provide the energy inputs and emission outputs. 3.3. Parts manufacturing/ remanufacturing Electric energy is the main energy input for engine newly manufacturing and remanufacturing, 8,266.36 MJ (2,296.21 kilowatt-hours [kWh]) of electric energy is required [15] for a new diesel engine manufacturing, and an LNG engine remanufacturing requires 3096.18 MJ (860.05 kWh).

Fig. 1. System boundary of newly manufacturing and remanufacturing

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3.4. Transportation of diesel /LNG engine The two types of engine are both sent to the 4S shop for sell by truck (carrying capacity: 50t consumes diesel only), and the average distance is also about 720 km. 3.5. Use of diesel /LNG engine The consumption of diesel and LNG in usage phase is calculated in Table 2. The energy inputs and emission outputs of diesel and LNG production are cited from the unit “diesel production” and “liquefied natural gas production” in CLCD. Because of the data deficiency about engine operation in CLCD, the emissions data of engine operation are cited from the public Ecoinvent 2.0 Database, the unit process are respectively “Operation, passenger car, diesel” and “Operation passenger, natural gas” because of the similar process. Table 2. Energy consumption of diesel and LNG engine

Characterization uses characterization factors to convert and combine the LCI results into factors of impacts to human and ecological health [13]. The characterization factors used in this paper are referred to as GBT2589-2008 [17] and IPCC2007/2002 [18]. Normalization uses a selected reference value to express indicator data in a way that could compare impacts categories [13]. Normalization reference value selected in this paper is cited from Wenzel et al., [19]. Table 5 shows the characterization and normalization results. Table 3. Life cycle inventory of newly manufactured diesel engine (Unit: Kg) Categories

Raw Diesel Materials Manufactmaterials engine transport uring production transport

Usage

Total

Coal

1.39E+03 4.04E-03 1.34E+03 1.06E-03 5.47E+03 8.21E+03

Crude oil

6.14E+01 4.91E-02 7.99E+00 1.44E-02 7.71E+04 7.72E+04

Natural gas 1.28E+01 8.13E-04 1.21E+01 2.39E-04 3.85E+01 6.34E+01 CO

1.77E+00 1.79E-02 4.71E-01 3.72E-04 7.27E+02 7.29E+02

CO2

2.73E+03 1.26E-01 2.09E+03 5.26E-02 2.25E+05 2.30E+05

Item

Diesel engine

LNG engine

SO2

7.19E+00 2.03E-04 7.28E+00 6.50E-05 1.73E+02 1.88E+02

Driving distance

300,000 km

300,000 km

NOx

4.43E+00 2.03E-03 6.02E+00 1.59E-03 6.34E+02 6.44E+02

Fuel efficiency

25 L/100 km

3

26.5 m /100km

CH4

6.77E+00 8.53E-04 6.18E+00 2.47E-04 1.31E+03 1.32E+03

Density

0.85 kg/L

0.716kg/m3

H2S

2.88E-02 1.96E-07 1.00E-03 5.65E-08 3.00E-01 3.30E-01

Total mass

63,750 kg

56,922kg

HCL

2.58E-01 1.48E-06 5.90E-01 3.80E-07 1.94E+00 2.79E+00

3.6. Old engine recycling Both of the newly manufactured and remanufactured products are recycled for another remanufacturing period; therefore, the analysis about this phase is conducted in the next system, that is to say that, the materials and energy required and emissions generated in the “old engine recycling” are considered in the next remanufacturing process. “Old engine recycling” in fact is included the whole remanufacturing process. From above analysis, the final life cycle inventory (LCI) results of the two engines are shown in Table 3 and 4, in which the materials and energy input into engine newly manufacturing and remanufacturing are quantitative converted into the primary energy of “Coal”, “Crude oil ” and “Natural gas”. The environmental burdens of energy input and emissions output are cited from CLCD. 4. Life cycle impact assessment According to ISO 14042, life cycle impact assessment (LCIA) should at least include the following steps: classification, characterization, and normalization. In this LCA study, five environmental impacts categories are assessed, which are: Global warming potential (GWP); Acidification potential (AP); Nutrient enrichment potential (EP); Photochemical ozone formation potential (POCP); and Primary energy demand (PED). PED includes three nonrenewable resources (coal, crude oil and natural gas). The base method for the analysis is the CML 2000 (baseline) developed by Guinèe et al. [16].

CFCs

1.28E+01 9.48E-05 2.82E+01 7.90E-12 4.21E-05 4.10E+01

BOD

4.84E+00 9.65E-05 1.13E-01 8.76E-05 4.70E+02 4.75E+02

COD

5.57E+00 3.93E-04 3.90E-03 1.03E-04 5.51E+02 5.57E+02

NH4

2.94E-02 1.79E-05 1.90E-01 2.48E-06 1.28E+01 1.30E+01

Table 4. Life cycle inventory of a remanufactured LNG engine (Unit: Kg) Additional Old diesel LNG RemufactCategories materials engine engine uring production transport transport Coal

Usage

Total

5.31E+02 6.76E-01 5.02E+02 6.76E-01 1.41E+03 2.44E+03

Crude oil 6.10E+01 9.20E+00 2.99E+00 9.20E+00 8.40E+02 9.22E+02 Natural 7.90E+00 1.52E-01 4.53E+00 1.52E-01 7.00E+04 7.00E+04 gas CO 4.47E-01 2.37E-01 1.76E-01 2.37E-01 4.60E+02 4.61E+02 CO2

9.98E+02 3.35E+01 7.82E+02 3.35E+01 1.92E+05 1.94E+05

SO2

1.14E+01 4.14E-02 2.73E+00 4.14E-02 7.77E+01 9.19E+01

NOx

2.76E+00 1.01E+01 2.25E+00 1.01E+01 1.14E+02 1.39E+02

CH4

3.13E+00 1.57E-01 2.31E+00 1.57E-01 5.13E+02 5.19E+02

H2S

5.23E-01 4.49E-05 3.75E-04 4.49E-05 2.42E+00 2.95E+00

HCL

1.90E-01 2.42E-04 2.21E-01 2.42E-04 1.45E-01 5.57E-01

CFCs

1.73E+00 5.01E-09 1.06E+01 5.01E-09 5.19E-04 1.23E+01

BOD

1.17E+00 5.58E-02 4.24E-02 5.58E-02 1.90E+01 2.03E+01

COD

1.42E+00 6.58E-02 1.46E-03 6.58E-02 2.33E+01 2.48E+01

NH4

1.14E-02 1.58E-03 7.11E-02 1.58E-03 3.07E+01 3.08E+01

5. Result and discussion 5.1. Entire life cycle comparison From Table 3 and 4, most items of the environmental impacts are reduced to a certain extent by LNG engine

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remanufacturing. Fig.2 shows the detailed LCI result of each item, Because the values of the data span to a long range, a log scale is used to pull it down to a more tractable range. It can be found that the largest reduction item by LNG remanufacturing is achieved in HCL and NOx, which account for 80.00% and 78.46% of the total emissions in manufacturing. Regarding resources consumption, the greatest savings is observed in crude oil consumption, which accounts for 98.52% of the total crude oil consumption in manufacturing. However, several items such as natural gas consumption and H2S emission are much increased due to the consumption and combustion of LNG during the LNG engine usage stage.

Fig. 2. LCI results comparison of the two engines

Based on Table 5, Fig. 3 presents the normalization results percentage comparison of a remanufactured LNG engine compared with the newly manufactured diesel engine. It is clearly found that, the reduction in AP and EP are most distinct; PED, GWP, AP, EP, and POCP respectively be reduced by 42.62%, 46.42%, 69.61%, 71.34% and 43.90%.

Fig.3. Environmental impacts comparison of the two engines.

5.2. Environmental impacts of different life cycle stages for two engines From Table 5, Fig. 4 and 5 illustrate the environmental impacts of different life cycle stages of the two engines. A log scale is also used here to put the data to a more tractable range. It is clearly showed that, all of the environmental impacts are predominant by both of the engine usage stage. In the life cycle of a newly manufactured diesel engine, PED and GWP are two main environmental impact categories and largely determined by raw material production and engine usage. Materials and engine transport stages account for only a small fraction of total environmental impacts. It is worth mentioning that, POCP contribute large portion in raw materials production phase due to more CO emits. As to the life cycle of LNG engine remanufacturing, components remanufacturing and LNG engine usage contribute the most results of PED, GWP, and AP due to large electricity and LNG consumption. The stages of old diesel engine and LNG engine transport create more influences in EP due to the fuel combustion.

Table 5 Life cycle impact of manufactured diesel and remanufactured LNG engine Mass(kg) Impact Substances category Manufacturing Remanufacturing

Characterization

PED

GWP

AP

EP

POCP

factor

Coal

8.21E+03

2.44E+03

0.714 Kg ce

Crude oil

7.72E+04

9.22E+02

1.429 0.909

Natural gas

6.34E+01

7.00E+04

CO2

2.30E+05

1.94E+05

1

CH4

1.32E+03

5.19E+02

25

NOx

6.44E+02

1.39E+02

320

CO

7.29E+02

4.61E+02

2

SO2

1.88E+02

9.19E+01

1

NOx

6.44E+02

1.39E+02

0.7

H2

3.30E-01

2.95E+00

1.88

HCL

2.79E+00

5.57E-01

0.88

Characterization Result Manufacturing Remanufacturing

Normalization Result Reference value Manufacturing Remanufacturing

1.16E+05

6.67E+04

828

1.40E+02

8.06E+01

4.71E+05

2.52E+05

8700

5.41E+01

2.90E+01

6.42E+02

1.95E+02

36

1.78E+01

5.42E+00

1.04E+03

2.99E+02

62

1.68E+01

4.82E+00

3.11E+01

1.75E+01

0.65

4.79E+01

2.69E+01

Kg COeq

Kg SO2eq

NH4

1.30E+01

3.08E+01

3.44

NO

6.44E+02

1.39E+02

1.35

COD

5.57E+02

2.48E+01

0.23

CO

7.29E+02

4.61E+02

CH4

1.32E+03

5.19E+02

0.03 Kg 0.007 C2H4 eq

Kg NO3eq

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7. Conclusion and recommendation

Fig.4. Life cycle environmental impacts of the manufactured diesel engine

Fig.5. Life cycle environmental impacts of the remanufactured LNG engine

6. sensitivity analysis Sensitivity analysis is conducted to measures the extent that changes in the LCI results and characterization models affect the impact indicator results [13]. Because engine usage stage brings the predominant contribution to environmental impacts, the variation of engine use lifetime may cause great change of the result, it is necessary to conduct the sensitivity check for engine usage in “Fuel production” and “Engine operation”. In this study, single factor sensitivity analysis method is used for significant data elements, “driving distance” is considered as the single factor, and the sensitivity analysis results are shown in Table 6. Table 6 Sensitivity analysis results for two engines use Sensitivity of fuel production (%) Sensitivity of engine operation (%) Impact category Manufactured Remanufactured Manufactured Remanufactured diesel engine LNG engine diesel engine LNG engine PED

98.2

98.7

0

0

GWP

14.6

32.9

83.6

63.1

AP

30.6

75.7

65.9

7.3

EP

21.4

18.2

77.1

43.9

POCP

31.8

31.5

67.6

68.1

From Table 6, it is clearly found that for both fuel production, PED is much sensitive to “driving distance”, GWP as well as POCP of both engines operation is relatively sensitive to “driving distance”. It is also showed that AP is much closely related to the LNG fuel production, AP and EP are closely related to diesel engine operation.

This study compared the energy consumption and environmental emissions for a newly manufactured diesel engine and remanufactured LNG engine based on LCA methodology. Five impact categories are considered: PED, GWP, AP, EP and POCP. The results point to the fact that LNG engine remanufacturing can largely reduce the energy consumption and environmental emissions, the reduction is mainly because of materials reuse and less emissions. It is also showed that in the life cycle of the two engines, environmental impacts are predominant by engine usage, and engine use lifetime is the determining factor for environmental impacts. The fuel of diesel be changed to the LNG is no doubt increased the consumption of natural gas, and the engine remanufacturing requires added labor, energy, and processing capital to recover the raw materials. Meanwhile, for LNG engine remanufacturing, due to the uncertainties and unknown conditions of the returned old products, the environmental benefits are not as the same, especially in engine remanufacturing stage. Nevertheless, because the predominant benefits are mainly in use stage, the advantages of LNG engine remanufacturing are still obviously. This study only considered five mid-point environmental impacts categories and neglecting some other categories (such as ozone depletion potential (ODP)), on the other hand, end-point environmental impacts are not take into account. It is challenging to incorporate more environmental impacts categories and even further end-point environmental impacts into evaluation, further efforts are needed. It is must state that, compared with previous LCA researches about engine remanufacturing, this study considered the LNG engine remanufacturing and extend the system boundary to engine usage stage, which makes the LCA study on this field be more complete and meaningful. Acknowledgements: The authors gratefully acknowledge the support of Jinan Fuqiang power Co., LTD, Zhangjiagang Furui Special Equipment CO., LTD and the National Basic Research Program of China (Grant No. 2011CB013406). References [1] Hu ZG, Yuan JH, Hu Z. Study on China's low carbon development in an Economy Energye Electricitye Environment framework. Energy Policy 2011; 39:2596-2605. [2] Steinhilper R. Remanufacturing: the Ultimate Form of Recycling. Disponívelem.1998. http://www.reman.org/Publications_main.htm(accessed 15.06.12.). [3] Guide J, VDR, Jayaraman V, Srivastava R, Benton WC. Supply-Chain management for recoverable manufacturing systems. Interfaces 2000;30 (3): 125-142. [4]Smith VM, Keoleian GA. The value of remanufactured engines life-cycle environmental and economic perspectives. Journal of Industrial Ecology 2004; 8 (1-2):193-221.

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