Diesel Engine Block Remanufacturing: Life Cycle Assessment · Life cycle assessment (LCA) is a...

Diesel Engine Block Remanufacturing: Life Cycle Assessment

Hong-Chao Zhanga*, Tao Lib, Zhichao Liub and Qiuhong JiangbaDepartment of Industrial Engineering, Texas Tech University, Lubbock, TX, USAbSchool of Mechanical Engineering, Dalian University of Technology, Dalian, China

Abstract

There has been a growing interest in remanufacturing during the past decade, since it offers manyadvantages to our economy. However, the qualification and quantification of the benefits ofremanufacturing compared to original manufacturing remain confusing to us due to the difficultiesof data collection in complex production processes and the lack of accurate and convincedevaluation method. Life cycle assessment (LCA) is a “cradle to grave” approach for assessingindustrial products and systems, which enables to estimate the cumulative environmental impactsresulting from all stages in a product life cycle. In this book, taking a diesel engine as a case study,a comprehensive LCA is conducted for remanufactured diesel engines, aiming to identify thenegative impact on the environment during the whole life cycle and to analyze the potential thatremanufacturing had in terms of energy savings and environment protections. In order to demon-strate the environmental benefit of remanufacturing, the environmental impacts achieved in thestudy are compared with a newly manufactured counterpart. The results show that remanufacturingof a diesel engine has lesser contribution to all the environmental impact categories when comparedto its original manufacturing; the greatest benefit is EP which is reduced by 79 %, followed by GWP,POCP, and AP which can be reduced by 67 %, 32 %, and 32 %, respectively.

Introduction

BackgroundResource and Environmental ProblemGlobal emissions of carbon dioxide (CO2) – the main cause of global warming – increased by 3% in2011, reaching an all-time high of 34 billion tons in 2011. In 2011, China’s average per capita CO2

emissions increased by 9 % to 7.2 t CO2 (Jos et al. 2012). The International Energy Outlook 2013(IEO2013) projects that world energy consumption will grow by 56 % between 2010 and 2040, andthe industrial sector continues to account for the largest share of delivered energy consumption; theworld industrial sector still consumes over half of global delivered energy in 2040 (IEA 2013).Statistics show that according to the present automobile growth, the volume of the end-of-lifeautomobiles will reach up to six million by 2015, and the large quantity of the discarded cars andengines will lead to resource waste and environment pollution. Increasingly serious resourceconsumptions and environment problems have attracted more and more attention by the societyand businesses. The government is establishing legislations and policies to encourage manufacturersto conduct green design and to explore methods for minimizing the effects of their activities on theenvironment (Zhang and Yu 1999; Kaebemick et al. 2003; MlastasPaul and Zimmemm 2003).

*Email: [email protected]

*Email: [email protected]

Handbook of Manufacturing Engineering and TechnologyDOI 10.1007/978-1-4471-4976-7_111-1# Springer-Verlag London (outside the USA) 2014

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The rapid depleting metal resources bring about a rigorous challenge to car components manu-facturers and halt economic development of China. Statistics show that most of the emissions aregiven out by the processes associated manufacturing industry, among which the metal processingoperations have a major share in the energy consumption. For instance, heavy-duty truck engineswith a large amount of steel and aluminum contribute significantly towards CO2 emissions. Besides,more than 80 % of industrial raw materials are dependent on the supply of mineral resources fromwithin China, and resource reserve shortage has become a major restriction for the development ofthe equipment manufacturing industry.

Modern manufacturing industry is facing the problem of how to reduce the environmental impactsof manufacturing. Some experts have put forwards four steps: understand the sources of the impact,quantify the environmental impact, identify improving opportunities, and then apply impact reduc-tion strategies and assess the effectiveness. Quantifying the environmental impact bridged thepreceding and the following when considering reducing the environmental impacts and quantifyingthe differences between a new strategy and traditional mode. There are two major problems inquantifying an impact in manufacturing: (1) manufacturing is not a stand-alone system and (2) bothinputs and outputs of manufacturing are closely linked to other systems and processes. Duringenvironmental impact control, the impact may shift from one process to another or from one lifecycle stage to another. Due to the two complexities, life cycle assessment (LCA) has to be used fora comprehensive and reliable assessment.

Development of RemanufacturingBefore remanufacturing, material recycling is always applied as product end-of-life strategy.Material recycling could return the consumed product to their original raw material form to beused again, but it requires added labor, energy, and processing capital to recover the raw materials.Normally, the relative costs of material, labor, energy and the contribution of plant and equipmentare the major concerns in product manufacturing. Remanufacturing could preserve much of thisvalue while adding a second life to the product. In contrast, recycling shreds the product in anattempt to recover only the material value. Little or none of the other residual values in the productare retained. Reuse could save the labor from original processing and also retain the function andthe design. The material recovery value chain of recycling, remanufacturing, and reuse is shownin Fig. 1.

Remanufacturing could repair degraded components and put the product back into service, thusretaining the value of the extracted and refined materials (Kumar et al. 2007). Steinhilper saidremanufacturing can avoid between 38 % and 53 % of carbon dioxide generated from newproduction in the 2010 International BIG R Show (Abby 2011). The remanufacturing of vehicles

MaterialExtraction

MaterialProcessing

ComponentFabrication

ProductAssembly

Distribution Use

Recycling

Remanufacturing

Reuse

• Material value

• Product residual value• Energy from casting, machining, etc.

• Labor from original process• Function/design intention

Fig. 1 The material recovery value chain of recycling, remanufacturing, and reuse


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dates back to the 1940s. In 1947, a take back scheme called “Exchange Parts Program”was launchedby Volkswagen to meet raw material shortages after World War II. The program significantlyreduced the material and energy consumption for a large proportion of the components.

Engine remanufacturing is a process of recovering the performances of the used engine afterserious remanufacturing processes based on remanufacturing standard. Being different from theoriginal engine manufacturing and traditional engine overhaul, engine remanufacturing begins withused engine reverse logistics, taking repairable components as processing objects, going throughdisassembly, cleaning, inspection, repairing, and reassembly processes. Once the product isdisassembled and the parts are recovered, the process concludes with an operation not too differentfrom the original manufacturing. Disassembled parts are inventoried, just like purchased parts, andmade available for final assembly. It is being realized that a diesel engine remanufacturing too hasbetter environmental performance than its original manufacture because of the fact that the mate-rials’ shaping processes such as molding, casting, etc. can be avoided. Professor Xu from theNational Key Laboratory for Remanufacturing said that in essence, parts remanufacturing cansave over 70 % of material costs, cut energy consumption by 60 %, and lower overall cost by50 % (Xu 2007). Since 2008, China has been trying to set up several auto parts remanufacturingbases under the direction of the National Development and Reform Commission. However, qual-ification and quantification of the benefits of diesel engine remanufacturing compared to originalmanufacturing remain unsolved due to the difficulties of data collection in complex productionprocesses and the lack of accurate and convincing evaluation methods.

Remanufacturing a qualitative transition of engine, it could give a second service life to an enginewith advantages of high quality and efficiency and low cost and pollution. Remanufacturingimproves sales volume and profit for enterprises as well as brings about considerable environmentalbenefits.

Life Cycle Assessment (LCA) MethodLife cycle assessment (LCA) is a “cradle to grave” approach for assessing industrial products andsystems, which enables the estimation of the cumulative environmental impacts resulting from allstages in a product life cycle, often including impacts not considered in more traditional analyses(EPA 2006).

According to the ISO 14040 and 14044 standards, an LCA consists of the following fourcomponents (see in Fig. 2):

Goal and scope definition

Inventory analysis

Impact assessment

Inte

rpre

tation

Application :• Product development and improvement• Strategy planning• Public policy making• Marketing• Others

Fig. 2 Framework of product life cycle assessment


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1. Goal and scope definition – Determine the type of information that is needed to add value to thedecision-making process. From EPA 2006, the following six basic decisions should be made atthe beginning of the LCA process to make effective use of time and resources:

(a) Define the goal(s) of the project.(b) Determine what type of information is needed to inform the decision-makers.(c) Determine the required specificity.(d) Determine how the data should be organized and the results displayed.(e) Define the scope of the study.(f) Determine the ground rules for performing the work.

2. Life cycle inventory analysis – Quantify energy and raw material requirements, atmosphericemissions, waterborne emissions, solid waste, and other releases for the entire life cycle ofa product, process, or activity. EPA 1995 defined the following four steps of a life cycle inventory:

(a) Develop a flow diagram of the processes being evaluated.(b) Develop a data collection plan.(c) Collect data.(d) Evaluate and report results.

Life cycle inventory (LCI) analysis is the most labor-intensive, time-consuming, and costlyprocess. Inventory analysis involves the collection of data and calculations in order to quantifythe inputs and outputs to the product system over its entire life cycle (ISO 1999).

Currently, the most commonly used inventory analysis methods include simplified LCI,process-based LCI, matrix-based LCI, economic input–output LCI, hybrid LCI, etc. The com-parisons of the major LCI approaches are shown in Table 1.

3. Life cycle impact assessment – Assess the potential human and ecological effects of energy,material usage, and environmental releases, as identified in the inventory analysis.

The following steps comprise a life cycle impact assessment:

Table 1 Comparison between the different LCI approaches

ItemsProcess-basedLCI

EIO-basedLCI

Hybrid approach

Tiered hybridanalysis IO-based hybrid analysis

Integratedhybrid analysis

Datasources

Mass andenvironmentalflows of eachprocess

Commodityandenvironmentalflows persector

Commodity andenvironmental flowsper sector andprocess

Commodity andenvironmental flows persector and process-based LCI

Commodity andenvironmentalflows per sectorand process

Datareliability

High Medium tolow

Depends Medium to high High

Datauncertainty

Low Medium tohigh

Depends Medium to low Low

Systemboundary

Incomplete Complete Complete Complete Complete


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(a) Selection and definition of impact categories – identifying relevant environmental impactcategories (e.g., global warming, acidification, terrestrial toxicity)

(b) Classification – assigning LCI results to the impact categories (e.g., classifying carbondioxide emissions to global warming)

(c) Characterization – modeling LCI impacts within impact categories using science-basedconversion factors (e.g., modeling the potential impact of carbon dioxide and methane onglobal warming)

(d) Normalization – expressing potential impacts in ways that can be compared (e.g., comparingthe global warming impact of carbon dioxide and methane for the two options)

(e) Weighting – emphasizing the most important potential impacts

In conclusion, LCA is conducted to calculate the final environmental impacts indicator by

EI ¼Xn

j¼1

Vk �

Xm

i¼1

EIi � Gi

Rk

0BBB@

1CCCA (1)

where EI is the final environmental impact indicator, Gi is the value of ith substance in life cycleinventory, EIi is characterization factor of ith substance to kth indicator, k ¼ 1 ~ 5, Rk is thereference value of kth indicator, Vk is the weight factor of kth indicator,m is the number of substancerelated to kth indicator, and n is the number of the indicators.4. Life cycle interpretation – Identify, quantify, check, and evaluate information from the results of

LCI and LCIA and communicate them effectively (ISO 1998). Within the ISO standard, thefollowing steps to conducting a life cycle interpretation are identified and discussed:

(a) Identification of the significant issues based on the LCI and LCIA(b) Evaluation which considers completeness, sensitivity, and consistency checks(c) Conclusions, recommendations, and reporting

An LCA can help decision-makers select the product or process which results in the least impactto the environment. In this paper, a comparative life cycle assessment is conducted for an originallymanufactured diesel engine and compared with its remanufactured counterpart, aiming to identifythe negative impact on the environment during the whole life cycle and analyze the potential thatremanufacturing possesses in terms of energy savings and environmental protections.

Technical Processes of Engine Remanufacturing

Technical process flows of engine remanufacturing (shown in Fig. 3) includes disassembly, classi-fication and cleaning, inspection, repairing, reassembly, etc.

1. Full-Scale DisassemblyDisassembly can be defined as the systematic separation of an assembly into its components,

subassemblies, or other groups (Lambert and Gupta 2005). It is an important process in material


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and product recovery since it allows for the selective separation of desired parts and materials.During the engine disassembly, the quick wear parts, such as the piston assembly, main shaftbushing, oil seal, rubber hose, and cylinder head gasket, are discarded directly. These componentsalways cannot be remanufactured or with no remanufacturing value, and they will be substitutedby the new parts when reassembling. The major components after engine disassembly are shownin Fig. 4; some quick wear parts are shown in Fig. 5.

2. Components CleaningAll the parts coming from the disassembly process are cleaned, and the cleaning process

involves washing away dirt and dust from the parts as well as degreasing, deoiling, derusting, andfreeing the parts from old paint (Steinhilper 1998). Several cleaning methods can be appliedaccording to the different materials and contaminations, including pyrogenic decomposition,chemical cleaning, ultrasonic cleaning, and liquid spraying.

3. Inspection and IdentificationInspection of disassembled and cleaned parts is required to determine their reusability and

reconditionability. According to Steinhilper (Steinhilper 1998), there are two important aspect ofinspection in remanufacturing:

Used engine Disassembly Cleaning Inspection Repairing

Parts can be remanufactured

Parts can not be remanufactured

Reassembly Inspection

Recycling

TestingCoatingRemanufactured

engine

Recycling New parts

Intact partsWearing parts

Fig. 3 Technical process flows of engine remanufacturing

Fig. 4 Major components after disassembly


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• Specification of criteria and condition characteristics required for the determination of thecondition of the components

• Development and application of suitable and affordable testing equipment

The testing equipment used for the testing of new parts is generally used after reconditioningthe disassembled parts. During inspection, the components are sorted after testing, those whichcan be reused directly, such as inlet pipe assembly, manifold, oil pan, and timing gear covers etc.,are loaded into the warehouse for reassembly; the failure components which can be repaired, suchas cylinder block assembly, connection rod assembly, crankshaft assembly, fuel injection pumpassembly, and cylinder head assembly etc., are prepared for remanufacturing.

4. Repairing for the Components Which Can Be RemanufacturedSeveral methods and technologies can be applied when repairing the failure parts, for example,

the advanced surface technology applied in surface dimension restoration to achieve a betterperformance compared with original parts, or mechanical manufacturing technology applied toreprocess the remanufactured parts to satisfy the tolerance scope for assembly.

5. ReassemblyThe parts are reassembled into a remanufactured product using the same power tools and

equipment used in the assembly of new parts (Steinhilper 1998).Then the remanufactured engine will go through testing, coating, and package processes. The

effect drawings of the used engine before and after remanufacturing are shown in Figs. 6 and 7.

Case Study: LCA-Based Evaluation of Diesel Engine Block Remanufacturing

Goal and Scope DefinitionThe goal of this study is to analyze the energy consumptions and environmental impacts of originalremanufacturing of a diesel engine with the perspective of total life cycle. Resource and energyconsumptions and air/water emissions are carried out and five environmental impacts which are

Fig. 5 Quick wear components


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Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), andAbiotic Depletion Potential (ADP) are assessed in this LCA.

The engine evaluated in this study is WD615.87 with in-line 6-cylinder, water-cooled, andturbocharged engine having a total displacement of 9.726 L. In this LCA, functional unit is definedas “300,000 km driven using a WD615-87 diesel engine.” The major technical parameters of thediesel engine under analysis are shown in Table 2.

A cradle to gate boundary scope was selected when analyzing the life cycle of the remanufactureddiesel engine, beginning with the used engine recycled back to the workshop through disassembly,cleaning, refurbishing, and reassembly. Due to time constraint and technical restrictions, it isdifficult to track the usage information of a remanufactured diesel engine; it is assumed accordingto the remanufacturer’s assurance. A remanufactured engine has the quality as good as a new engineand, therefore, meets the same fuel requirements as an originally manufactured engine. Moreover, asfor the period of end-of-life disposal, the remanufactured engines are recycled back for another

Fig. 6 Used diesel engine

Fig. 7 Remanufactured diesel engine


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remanufacturing period; therefore, the phase end-of-life disposal is excluded from the evaluationscopes. The components considered in our analysis include the six parts which can be manufacturedin the workshop, including cylinder block, cylinder head, crankshaft, connection rod, gearbox, andthe accessories which are purchased from outside but can also be remanufactured. It was investi-gated that an engine can be remanufactured three to five times. As the failure modes and repairmethods are usually different each time and the remanufactured engine has not reached service life,the given remanufacturing cycle has been considered as the first one. Figure 8 shows the systemboundary of this life cycle assessment.

Life Cycle Inventory AnalysisData ResourcesMaterials Production The materials consumed in the engine components manufacturing aremainly steel, cast iron, and aluminum. As for remanufacturing, there are some additional materialssuch as kerosene, copper, nickel and diesel for refurbishing the components. The respectivequantities of the main materials used in manufacturing/remanufacturing are shown in Table 3.

The raw materials need to be extracted and refined from the minerals and then undergo variousremanufacturing processes to rebuild the engine parts. Energy and resources are used for thispurpose. Aluminum, cast iron, and diesel are the three major materials of diesel engineremanufacturing, which bring about large amounts of energy consumptions and environmentalemissions. The data related to energy requirements, air/water emissions of materials, mining, andproduction phases are referred from the Chinese Life Cycle Database (CLCD) developed by IKE,

Table 2 Technical parameters of WD615.87 diesel engine

Parameter Quantity Unit

Weight 850 Kg

Volume 9,726 ml

Rated power 213 kw

Rated speed 2,200 r/min

Torsion 1,160 N � mTorque speed 1,100–1,600 r/min

Natural resources

Used Engine Recycling

Energy

Components refurbishing

Cleaning

Air/wateremissions

Additional materials production

InspectionDisassembly

/ sorting

Components replaced by new

ReassemblyUsage

End of life disposal

Testing

Fig. 8 A simplified life cycle of diesel engine remanufacturing processes, indicating the system boundary


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China (Liu et al. 2010). The CLCD database can reflect the average production levels existingcurrently. The inventory of unit material production is shown in Table 4.

Reverse Logistics of the Used Diesel Engines According to the investigation, the used dieselengines for remanufacturing are all recycled back from the CNHTC 4S shop by truck (carryingcapacity: 10 t); there are about 170 4S shops in the mainland; the average distance Davg covered forthe old engine recycling is estimated by Eq. 2:

Davg ¼

Xm

i¼1

Di � Ni

Rtotal(2)

where Rtotal is the total recovery number of the used engines, Di is the recycling distance of the oneused engines in the ith 4S shop, and Ni is the number of the used engines recovered by the ith4S shop.

Then, the average distance can be obtained by the investigation, and Davg ¼ 800 km. It isassumed that the truck consumes gasoline only and the transportation inner the plant is ignored,

Table 3 Main materials used in manufacturing/remanufacturing

Materials for manufacturing Quantity (kg) Materials for remanufacturing Quantity (kg)

Steel 188.19 Nickel 0.388

Cast iron 578.83 Cast iron 9

Aluminum 39.9 Aluminum 10

Alloy 32.92 Diesel 14.91

/ / Kerosene 8.8

Table 4 Inventory of unit material production

Inventory(kg)

Production ofnickel

Production ofdiesel

Production ofaluminum

Production ofkerosene

Production of castiron

Coal 1.48E+01 8.58E-02 1.25E+01 1.27E+01 1.11E+00

Crude oil 1.60E+00 1.21E+00 5.11E-01 1.38E+00 4.78E-02

Natural gas 1.25E-01 6.04E-04 1.68E-01 1.04E-01 1.11E-03

CO 2.23E-02 4.02E-04 5.76E-03 1.91E-02 4.84E-04

CO2 2.85E+01 3.75E-01 2.25E+01 2.45E+01 2.21E+00

SO2 1.00E+00 2.62E-03 7.74E-02 8.65E-01 4.68E-03

NOx 1.25E-01 6.04E-04 5.56E-02 1.03E-01 2.33E-03

CH4 8.33E-02 2.05E-02 6.37E-02 7.16E-02 5.15E-03

H2S 6.25E-02 4.71E-06 4.69E-04 4.68E-02 1.11E-05

HCL 5.69E-03 3.04E-05 4.84E-03 4.89E-03 5.22E-05

CFCs 2.15E-08 6.60E-10 3.16E-10 1.84E-08 1.33E-02

BOD 6.02E-02 7.38E-03 9.77E-03 5.18E-02 5.72E-03

COD 6.25E-02 8.65E-03 1.48E-02 5.33E-02 5.98E-03

NH4 2.35E-04 2.01E-04 1.62E-04 2.27E-04 3.02E-05


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the energy consumption and emissions of unit distance when recycling can be obtained by CLCD(shown in Table 5).

Engine Disassembly When the used engines are recycled back to the workshop, they are usuallydisassembled by high-pressure air rifle; the average time for one engine disassembly is 300 min, andit will consume 30 m3 compressed air, which equals 1.2 kg when converted to standard coal.

Parts Remanufacturing The volumes of the materials for the component remanufacturing arequantified in the section of materials production. The energy consumptions for the six parts aremeasured during their remanufacturing processes. The detailed method for data gathering is stated insection “Data Collection in Parts Remanufacturing.”

Air/Water Emissions The data for the air/water emissions have been discussed in detail in the datacollection sheets. The different gases involved are CO2, CO, H2S, N2O, and chlorofluorocarbons(CFC). The water pollution emissions contains ammonia nitrogen, Biological Oxygen Demand(BOD) and Chemical Oxygen Demand (COD). The data about the energy demand and environ-mental emissions are all obtained from the CLCD fundamental database.

Data Collection in Parts RemanufacturingRemanufacturing processes are generally composed of several stages: disassembly, cleaning,testing, repair, inspection, updating, component replacement, and reassembly (Sherwood and Shu2000). The flow diagram of the six parts remanufacturing processes are illustrated for data gatheringand the resource and energy consumption of each part are collected from its remanufacturing line.Figures 9, 10, 11, 12, and 13 illustrate the data collection process of the cylinder block, cylinderhead, crankshaft, connection rod, gearbox, and flywheel.

Table 6 summarized the electricity and material consumptions of engine componentsremanufacturing; the main materials consumed in the engine remanufacturing are nickel, aluminum,cast iron, and kerosene and diesel. Energy and natural recourse consumption and environmentalemissions generated in these materials production can be obtained by CLCD.

UsageAccording to the remanufacturer’s assurance, a remanufactured engine has the quality as good asa new engine and, therefore, meets the same fuel requirements as an originally manufactured engine.It is assumed that the diesel engine is used in a truck, the energy consumed in the usage is mainlydiesel fuel production, and the emissions are generated in the diesel engine operation. The diesel fuelconsumed in the usage is calculated as follows:

Driving distance: 300,000 km, as is defined in the functional unitFuel efficiency: 24 ~ 26 L/100 km, using the average 25 L/100 km (Lambert and Gupta 2005)

Table 5 Inventory of the truck transportation process/tkm

Inventory Coal Crude oil Natural gas CO CO2 SO2 NOx

Mass (kg) 4.04E-03 4.91E-02 8.13E-04 1.79E-02 1.26E-01 2.03E-04 2.03E-03

Inventory CH4 H2S HCL CFCs COD NH4 Dust

Mass (kg) 8.53E-04 1.96E-07 1.48E-06 9.48E-05 3.93E-04 1.79E-05 9.350E-05


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Cleaning

Reman.1

Cleaning

Inspection

Cylinderblock

Reman.2

subsequentprocess 2

20.585kwh

2.3kwh

0.7kwh

Electricity

Coating material

5kg

Electricity

Shotblasting

Incinerationby pyrolysis

Electricity

Diesel7.5kg

0.375kwh

Electricity

0.933kwh

subsequentprocess 1

21.111kwh

Cast iron

Water3.75m3

9kg

Fig. 9 Detailed flow diagram of the cylinder block remanufacturing process (Reman.1 and Reman.2 refer to the cylinderliner substitution and the cylinder liner brush plating.)

Clean 1

Inspection

Reman. 1

Clean 2

Inspection

Remanufacturedcrankshaft

Reman. 2

Postprocessing

kerosene0.2kg

0.998kwh

2.67m3

Water(1,2)

1.169kwh

0.443kwhMagneticpowder

0.613kwh

0.443kwh 2.1kwh6.615kwh

Compressair

Coatingmaterial

30m35kg

Energy

Fig. 10 Detailed flow diagram of the crankshaft remanufacturing process (Clean 1, 2: high-pressure water jet cleaning;Reman. 1: silk hole repairing, polishing; Inspection: magnetic powder inspection; Reman. 2: crankshaft neck,connecting rod journal laser plating; Post-processing: crankshaft neck milling)


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Density of diesel: 0.85 kg/LMass of the diesel: 3,000 � 25 � 0.85 ¼ 63,750 kg

Clean 1

Inspection

Reman. 1

Clean 2

Inspection

Remanufacturedconnection rod

Reman. 2

Postprocessing

Kerosene0.6kg

0.299kwh

0.8m3Water(1,2)

3.64kwh

1.4kwhMagneticpowder

0.184kwh

1.4kwh

0.105kwh

ElectricityNickel

1.5kwh48g

Energy

3.75g

Fig. 11 Detailed flow diagram of the connection rod remanufacturing process (Clean 1, 2: high-pressure water jetcleaning; Reman. 1: bush substitution, boring, and milling; Inspection: magnetic powder inspection; Reman. 2: big holenano brush plating; Post-processing: polishing and quilted grinding of the big hole)

Clean 1

PolishingHigh temperaturedecomposition

Electricity

Diesel4.5kg

0.225kwh

Electricity

0.56kwh

Reman.

InspectionEnergy

Clean 2

Remanufacturedcylinder head

161.9kwh

13.44kwh

2.3kwhWater

1m3

Fig. 12 Detailed flow diagram of the cylinder head remanufacturing process (Clean 1: high-temperature decomposi-tion; Clean 2: dedicated cleaning machine; Reman.: valve pipe substitution, valve processing, and surface grinding)


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The energy inputs and emission outputs of 63,750 kg diesel production is cited from the unit“diesel production” in CLCD, and the air/water emissions of the engine operation is cited from theunit of “operation, passenger car, diesel” in the public ecoinvent 2.0 database.

Life Cycle InventoryThe energy consumptions for remanufactured diesel engines along with different life cycle stagesare shown in Table 7. Figure 14 is illustrated to show the inventory results more vividly, andlogarithmic processing is conducted in order to normalize the result to a more tractable range.

Three kinds of natural resources – coal, crude oil, and natural gas – are considered in theproduction of remanufactured diesel engines. It is obvious that the usage period will consume themost energy and generate the most air emissions; comparatively the used engine reverse logisticswill bring about little environmental load. The crude oil and CO2 are the biggest inventory sub-stances, followed by coal, CH4, NOx, COD, and SO2.

Life Cycle Impact AssessmentAlthoughmuchmore can be learned about the processes by considering the life cycle inventory data,an LCIA provides a more meaningful basis to make comparisons. Based on the life cycle inventorydata, LCIA is conducted for the environmental impacts mentioned above according to ISO 14042(Yang et al. 2002). At each process in remanufacturing, the inventory data sets, including resource

Cleaning

Reman.1.19kwh

Remanufactured gearbox and fly wheel

PolishingHigh temperaturedecomposition

Electricity

Diesel2.91kg

Fig. 13 Detailed flow diagram of the gearbox and flywheel remanufacturing process

Table 6 Energy and resource consumption of engine components remanufacturing

ComponentsCleaning Inspection Reman. Post-processing(kWh) (kWh) (kWh) (kWh)

Crankshaft 1.611 0.886 3.269 6.615

Connection rod 0.483 2.8 5.14 0.105

Cylinder block 3.608 0.7 2.8875 17.694

Cylinder head 3.085 13.44 161.9 /

Gearbox 0.1 / 0.595 /

Flywheel 0.162 / 0.595 /

Else 24.76 / 2.243 /


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Tab

le7

Inventoryof

lifecyclestages

ofengine

remanufacturing

Inventory

(kg)

Productionof

materials

Usedengine

reverselogistics

Com

ponents

remanufacturing

Usage

Total

Production

ofnickel

Productionof

alum

inum

Production

ofdiesel

Productionof

kerosene

Productionof

castiron

Dieselfuel

productio

nOperatio

n

Coal

5.74

124.95

1.28

111.63

9.86

2.24

452.01

5468.48

/6176.19

Crude

oil

0.65

5.11

18.03

12.16

0.43

27.17

2.7

77105.46

/77171.71

Natural

gas

0.08

1.68

0.01

0.92

0.01

0.45

4.02

37.13

/44.30

CO

0.01

0.06

0.01

0.17

4.00E-03

9.92

0.16

27.72

701.54

739.59

CO2

11.07

224.91

5.59

215.31

19.66

69.85

703.94

23910.76

201300

226461.09

SO2

0.40

0.77

0.04

7.61

0.04

0.11

2.45

168.64

6.375

186.44

NOx

0.08

0.56

0.01

0.9

0.02

1.13

2.03

39.83

595.34

639.90

CH4

0.03

0.64

0.31

0.63

0.05

0.47

2.08

1306.98

3.767

1314.96

H2S

0.02

4.69E-03

7.02E-05

0.41

9.86E-05

1.09E-04

3.37E-04

3.00E-01

/0.74

HCL

2.21E-03

0.05

4.54E-04

0.04

08.18E-04

0.2

1.94

/2.23

COD

0.02

0.15

0.13

0.47

0.05

0.22

0.06

552.90

/554.00

NH4

9.13E-05

1.62E-03

3.00E-03

2.00E-03

2.69E-04

0.01

1.31E-03

13.32

/13.34


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extraction and air/water emissions, were collected and classified into the impact categories. Subse-quently, through characterization and normalization processing, the environmental impacts werecalculated for each category.

ClassificationThe LCI results are organized and combined into the impacts categories by classification. The mainimpact categories to be investigated under this project are Global Warming Potential (GWP),Acidification Potential (AP), Eutrophication Potential (EP), Photochemical Ozone Creation Poten-tial (POCP), and Abiotic Depletion Potential (ADP).

CharacterizationCharacterization provides a way to directly compare the LCI results with each impact category.Based on the inventory data, the results of LCI, such as raw material consumption, energyconsumption, and air/water emissions, were converted into impact indicators by multiplying thecharacterization factor with IPCC, CML, andWMOmethodologies (Yang et al. 2002; WMO 1992).Table 8 shows the results of characterization of the remanufacturing processes.

Normalization and WeightingNormalization expresses the potential impacts in ways that can be compared with an equivalentvalue, and weighting assigns weights to the different impact categories based on their perceivedimportance or relevance, which are based on the characterization results. Normalization andweighing of five environmental impacts of remanufacturing are shown in Table 9. The resultsshow that the environmental impacts of manufacturing and remanufacturing are 1.72 and 0.86,respectively (not including ADP).

InterpretationLife cycle interpretation is a systematic technique to identify, quantify, check, and evaluate infor-mation from the results of the LCI and LCIA.

0.0001

0.001

0.01

0.1

1

10

100

1000

10000

100000

1000000

Coal Crudeoil

Naturalgas

CO CO2 SO2 NOx CH4 H2S HCL COD NH4

Production of materials

Used engine reverse logistics

Components remanufacturing

Usage

Fig. 14 Log scale results of energy inputs and emission outputs by unit process


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Contribution analysis is conducted in order to quantify the contribution of the life cycle stages orgroups of processes compared to the total result and examined for relevance (EPA 2006). Environ-mental impacts of different life cycle stages after normalization are shown in Table 10.

Figure 15 illustrates the results of the environmental impacts as are presented in Table 10. Fromthe results, it can be seen that during the life cycle of diesel engine remanufacturing, the usage bringsabout most environmental impacts, especially GWP and AP; production of materials brings aboutlarger environmental impacts with regards to GWP and AP; and old diesel engine reverse logisticscan bring about less environmental impacts except POCP.

Table 8 Characterization results of diesel engine remanufacturing

Environmental impacts Substances Remanufacturing quantity (kg)Characterizationfactor Remanufacturing

ADP Steel and cast iron 9 1.66E-6 Kg Sbeq 2.98E-03

CML2002 Aluminum 10 2.53E-5

Nickel 0.388 4.18E-3

Coal 567.16 8.08E-7

Crude oil 60.06 9.87E-6

Natural gas 5.40 7.02E-6

GWP CO2 1266.26 1 Kg CO2eq 2886.24

IPCC2007 CH4 4.32 25

NOx 4.98 320

CO 10.33 2

AP SO2 11.43 1 Kg SO2eq 15.82

CML2002 NOx 4.98 0.7

H2S 0.44 1.88

HCL 0.29 0.88

EP NH4 0.02 3.44 Kg NO3eq 0.32

CML2002 COD 1.15 0.23

POCP CO 10.33 0.03 Kg C2H4eq 0.31

CML2002

Table 9 Normalization and weighing of environmental impacts of remanufacturing

Environmental impacts Equivalent valuea Remanufacturing WFb Result

GWP 8,700 0.34 0.83 0.862

AP 36 0.44 0.73

EP 62 5.16E-03 0.73

POCP 0.65 0.48 0.53aEquivalent value of the national standardization, 1990, ChinabWeighting factors according to the reduction target, 2000, China


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Comparisons with Newly Manufactured Engine

In order to demonstrate the environmental benefit of remanufacturing more vividly, the results of thestudy are compared with an LCA case of new manufactured diesel engine with the same type(Li et al. 2013).

The total energy inputs and emissions outputs during the life cycle of diesel engine manufacturingand remanufacturing are shown in Table 11.

Figure 16 illustrates the environmental emissions of diesel engine manufacturing andremanufacturing before usage more vividly.

Remanufacturing offers significant savings in coal and natural gas consumptions, which are73.85 % and 71.1 %, respectively. On the other hand, it causes a little more crude oil consumptiondue to the production of kerosene, diesel materials, and gasoline fuels which are consumed in usedengine remanufacturing.

Table 11 compares the environmental emissions during diesel engine manufacturing andremanufacturing, which shows that the remanufacturing process results in significant reductionsin the most relevant air/water emission categories. For example, the production of a new dieselengine produces 4.84 t of carbon dioxide, while diesel engine remanufacturing produces only 1.25 tof CO2. It should be noted that remanufacturing brings about more H2S emissions from fuelcombustion in old engine reverse logistics.

Table 10 Environmental impacts of different life cycle stages of remanufacturing after normalization

Environmental impacts

Processes of engine remanufacturing

Materials production Old engine reverse logistic Component remanufacturing Usage

GWP 0.12 0.05 0.16 53.18

AP 0.30 0.03 0.11 17.28

EP 3.39E-03 1.37E-03 2.90E-04 2.79

POCP 0.01 0.46 0.01 33.66

0.00

0.00

0.01

0.10

1.00

10.00

100.00

GWP AP EP POCP

Materials Production

Old engine reverse logistic

Components remanufacturing

Usage

Fig. 15 Environmental impacts of the different remanufacturing life cycle stages


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The environmental impacts of the manufacturing and remanufacturing strategies are comparedand presented in Fig. 17. It is evident that remanufacturing of a diesel engine has lesser contributiontowards all the environmental impact categories when compared with its manufacturing equivalent.The greatest benefit regarding environmental impacts is EP, which is reduced by 79 %, followed byGWP, POCP, and AP which can be reduced by 67 %, 32 %, and 32 %, respectively.

Conclusions

This study conducted a comparative LCA for a remanufactured diesel engine produced by ChinaSINOTRUK. The results obtained could be used in the future for engine designing from a life cycle

Table 11 Total energy inputs and emissions outputs during the life cycle of diesel engine manufacturing andremanufacturing

Categories Manufacturing Remanufacturing Energy savings

Resources (kg) Coal 2,703.74 707.71 1,996.03

Crude oil 104.13 66.24 37.89

Natural gas 24.81 7.17 17.64

Air emissions (kg) CO 15.37 10.33 5.04

CO2 4,844.01 1,250.33 3,593.68

SO2 14.44 11.43 3.01

NOx 11.83 4.72 7.11

CH4 13.42 4.21 9.21

H2S 0.03 0.44 �0.41

HCL 0.84 0.29 0.55

Water emissions (kg) BOD 5.23 0.95 4.28

NH4 0.05 0.02 0.03

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Coal Crudeoil

Naturalgas

CO CO2 SO2 NOx CH4 H2S HCL BOD NH4

Remanufacturing Manufacturing

Fig. 16 Environmental emissions of diesel engine manufacturing and remanufacturing


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perspective. The energies consumed in the engine component remanufacturing processes arecollected in the remanufacturing line, and all of them are showed in detailed process flows. Dueto time constraints and technical restrictions, it is difficult to track the usage information ofa remanufactured diesel engine; therefore, the usage of a remanufactured engine is regarded as thesame with a new manufactured diesel engine, and accurate energy consumptions during the usageperiod of remanufactured engines require more detailed investigation and survey to guarantee thequality of the LCA data.

During the life cycle of diesel engine remanufacturing, the usage brings about most environmentalimpacts, especially GWP and AP; production of materials brings about larger environmentalimpacts with regards to GWP and AP; and old diesel engine reverse logistics can bring about lessenvironmental impacts except POCP.

Being different from material recycling, remanufacturing “recycles” the value originally added tothe raw material, including the cost of labor, energy, and manufacturing operations. However,recycling requires added labor, energy, and processing capital to recover the raw materials.Remanufacturing could make greater economic contribution per unit of product than recycling bycutting down energy consumption and resources used for processing. From the analysis provided inthis paper, it can be concluded that remanufacturing of a diesel engine has lesser involvementtowards all the environmental impact categories when compared to its manufacturing alternate. Thegreatest reduction is EP, which is reduced by 79 %.

The results in Fig. 15 show that usage and production of the materials, mainly aluminum and castiron, brings about serious environmental problems. Future work will focus on building greaterefficiencies into the remanufacturing processes and greener energies, reusing a greater percentage ofend-of-life components, and developing more sustainable and energy-efficient materials for dieselengine. In the life cycle of remanufactured diesel engines, the environmental impacts are largelydetermined by diesel consumption, electric power, and material consumptions; thus, subsequentanalyses should focus on these aspects for further optimization.

References

Abby T (2011) Auto parts remanufacturing to be new emphasis in China. www.chinaautoreview.com/pub/CARArticle.aspx? ID ¼ 6137. Accessed June 2011

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

GWP AP EP POCP

Manufacturing Remanufacturing

Fig. 17 Environmental impacts of manufacturing and remanufacturing


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http://www.chinaautoreview.com/pub/CARArticle.aspx?%20ID%20=%206137



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Index Terms:

Diesel engine 7Environmental impact 2, 5, 18Life cycle assessment (LCA) 3Remanufacturing 2, 5, 7


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