01 impact of the lean technique of value stream mapping 2012/01 the impact of the lean... ·...

The Impact Of The Lean Technique Of Value Stream Mapping... 5The Impact Of The Lean Technique Of ValueStream Mapping In Indian Construction Sites

On Reducing Carbon Emissions

Ann Francis1 and Ashwin Mahalingam2

Abstract : The construction industry is responsible for a considerable amount ofCO2 and Greenhouse gas emissions. In the present day context, this isa cause of considerable concern. Can 'Lean' construction techniquesthat improve site productivity also improve site sustainability? Preliminaryevidence from other countries indicates that 'Lean' construction canindeed lead to reduced emissions on construction sites. This paperattempts to validate this notion on Indian construction sites and alsoattempts to compare the extent of productivity enhancement and emissionreduction across a spectrum of construction activities, in order toachieve a better understanding of where 'Lean' principles can be bestused for improving sustainability. We considered five different constructionactivities - Piling, Construction of Open Foundations, Slab Concreting,Blockwork and Fabricating Steel Trusses. We used Value Stream Mapping(VSM) - a popularly used and standardized 'Lean' technique to map thecurrent execution process for each of these activities, and optimizeproductivity using Lean techniques. Using simulation techniques, wesimulated the post-optimization performance of these activities. Bycomparing CO2 equivalent emissions in the original state and in theoptimized state for each activity type, we were able to assess the roleof Lean practices in promoting sustainable construction. Our resultsindicate that while Lean construction can lead to Green constructionacross all the activities that we considered, the extent of emissionreductions was highest in the construction of open foundations followedby block work and piling. Only negligible improvements were visiblein concreting and structural steel fabrication. Our findings are of relevanceto policy makers, practitioners and academics as they seek to make theconstruction industry more sustainable.

Keywords : Sustainability, Lean Construction, Value Stream Mapping, Simulation,

CO2 Equivalent Emissions.

1Sr. Engineer, Civil, Larsen & Toubro Construction, India. Email : [email protected] Professor, Indian Institute of Technology, Madras, India. Email : [email protected]

INTRODUCTIONThe construction industry has a significant impact

on the natural environment. Building construction

and operation accounts for 40% of the materials

and 33% of the energy used in the world economy

(Rees, 1999). While these facts are well known,

and the need for the construction industry to

embrace sustainability has been emphasized,

6 NICMAR-Journal of Construction Management, Vol. XXVII, No. 4, Oct.-Dec. 2012

researchers and practitioners have tended to focus

mainly on designing buildings that can be

sustainably operated. Green rating systems such

as LEED (Leadership in Energy and Environmental

Design) and GRIHA (Green Rating for Integrated

Habitat Assessment) provide credit for designing

buildings that are energy efficient, or which

optimize on resource consumption during design

and/or operations. While the sustainability of the

final product is addressed through these efforts,

the sustainability of the process of construction

of these products is often ignored (Melissa and

Robert, 2006). Carbon emissions from the

production and transportation of materials, use

of equipment and so on are not evaluated when

the sustainability of a construction project is

addressed. Often these can be quite significant

(Hendrickson and Horvath, 2000).

Traditionally, the objectives of the construction

phase of a project have been limited to minimizing

project costs and durations, and optimizing quality.

However, as Kibert (1994) notes, given global

environmental concerns and the impact that the

construction phase has on environmental quality,

modern construction processes must also address

issues of resource depletion and minimization of

environmental degradation. How then can the

practice of construction be made more sustainable?

Recently, 'Lean' construction has emerged as a

method through which construction practices can

be optimized to ensure timely and cost-effective

project delivery (Ballard and Howell, 2003). Can

these Lean practices also contribute to enhancing

the sustainability of construction practices? It is

to this question that we turn our attention in this

paper.

This paper is organized as follows: The next section

briefly reviews the literature on 'Lean' construction

and the existing evidence on the connection

between 'Lean' construction and sustainability.

Following this we describe our research

methodology and the way in which we evaluated

the enhanced sustainability of 5 sets of construction

practices after the introduction of 'Lean' practices.

We then present our results and conclude with

a discussion on the connection between Lean

construction and sustainability in the context of

Indian construction.

LITERATURE REVIEWThe Lean Construction Institute defines the term

‘Lean construction’ as “a production management-

based approach to project delivery”. Simply put,

‘Lean’ construction is an approach adapted from

the manufacturing industry, aimed at reducing

wastes and ensuring on-time delivery and

heightened customer satisfaction. The ‘Lean’

literature acknowledges seven potential kinds of

wastes in any process. These wastes are:

1. Waiting Waste

2. Motion Waste

3. Over-Processing Waste

4. Over production Waste

5. Transportation wastes

6. Inventory Wastes

7. Rework Wastes (Ohno, 1998)

Using Womack and Jones’ (1996) ‘Lean’ principles

of reducing these wastes by understanding and

improving value from a customer’s perspective,

and improving the ‘flow’ of work by reducing

obstacles, several researchers have attempted to

adapt ‘Lean’ to the construction industry (e.g

Koskela, 2000; Ballard and Howell, 2003). Ballard

and Howell (2003) operationalize ‘Lean

Construction’ in the form of a ‘Lean Project

Delivery System’ (LPDS) and show how tools such

as the ‘Last Planner’ system, and pull-based

scheduling (where downstream activities control

the productivity of upstream activities as opposed

The Impact Of The Lean Technique Of Value Stream Mapping... 7

to the traditional push-based system which does

the opposite) can reduce wastes and improve

construction performance. While most of this

literature cites examples from developed countries,

Nair and Mahalingam (2011) have shown how ‘Lean

Construction’ can be implemented in India. By

applying the ‘Value Stream Mapping’ tool to

construction projects in India, their analysis suggests

that ‘Lean’ principles can have significant beneficial

impacts on project duration.

With regards to the relationship between ‘Lean’

and ‘Green’, a few researchers have noted nil or

negative correlations between the use of ‘Lean’

practices and ‘Green’ outcomes. Rothenberg et al

(2001) find that ‘Lean’ practices did not lead to

reduction in emissions of Volatile Organic

Compounds (VOC); Cusumano (1994) argues that

‘Lean’ principles such as ‘just-in-time’ lead to traffic

congestion and increase in pollution due to more

frequent trips. However, a majority of the literature

indicates that ‘Lean’ practices and ‘Green’ outcomes

are positively correlated. The EPA (2003) proposes

that ‘Lean’ provides a platform that is highly focused

on waste minimization and pollution prevention

in an operational environment, and hence provides

an excellent foundation for environmental

management tools such as life cycle assessment and

design for the environment. Nahmens and Ikuma

(2011) suggest that ‘Lean’ construction provides

a more structured job-plan into which the ‘Green’

objectives can be easily incorporated. Peng and

Pheng (2011) in their study to investigate whether

‘lean’ production philosophy is applicable in precast

concrete factories to achieve sustainability, found

that for precast concrete column construction, 8.3%

of carbon emissions was reduced when the lean

production philosophy was adopted in the casting

yard. Klotz, Horman, and Bodenschatz (2007) also

opine that “By identifying and eliminating waste,

sustainable outcomes can be enhanced through

utilizing delivery processes that are better equipped

to maximize value generation by fulfilling the

unique needs of green building projects”. As

Huovila and Koskela (1998) note, the principles

of ‘Lean’ construction should converge with

sustainability objectives. Eliminating ‘waste’ should

mean minimization of resource depletion and

minimization of pollution, Adding ‘Value to the

Customer’ should mean business and

environmental excellence.

While the literature predominantly seems to reflect

the notion that utilizing ‘Lean’ practices can lead

to ‘Green’ outcomes, the following questions

remain unanswered:

1. Can ‘Lean Construction’ lead to enhanced

sustainability in the context of the Indian

Construction Industry?

2. If so, which construction activities can

yield the highest production efficiencies

and sustainability impacts through the use

of ‘Lean’ construction techniques?

This paper attempts to begin to answer these

questions. We next discuss our research

methodology.

RESEARCH METHODOLOGYIn order to answer our research questions identified

above, we selected five categories of construction

activities spread across four construction sites. All

sites involved the construction of multi-storied

commercial buildings. These 5 activities were:

1. Piling

2. Open Foundation

3. Slab Concreting

4. Block Work

5. Structural Steel Fabrication

Since considering a single activity might not be

representative, we chose to consider a range of

activities undertaken on construction sites. By


considering a variety of construction activities at

both the sub-structure and super-structure levels

that would be undertaken across the lifecycle of

a project, we hoped to compare the sustainability

impacts across activities due to the implementation

of ‘Lean’ practices.

For each type of activity selected, the Value Stream

Mapping (VSM) technique was applied to optimize

site operations. VSM is a ‘Lean’ tool that shows

a visual display of the f low of materials and

information through the production process. Value

stream mapping identifies the value-added activities

and non-value-added activities in a construction

sequence. Value Stream Mapping is often used

in process cycle-time improvement since it

demonstrates exactly how a process operates with

detailed timing of step-by-step activities (Picchi,

2000). It is also used for process analysis and

improvement by identifying and eliminating time

spent on non-value-adding activities. Many studies

suggest that VSM is one of the best visual tools

that show the f low of both information and

material. Hence it is a very useful tool to understand

the generation and flow of value and waste during

project processes for analyzing the environmental

impact of construction processes.

To start with, a Current State Map (CSM) was

drawn for each activity, plotting the various sub-

activities and their durations, in the manner in

which they were being executed at site. A carbon

footprint calculation was then performed to

evaluate the extent of Greenhouse Gas (GHG)

emissions from the current project. While there

are several GHGs in the earth’s atmosphere (e.g.

CO2, CH4, N2O), the contribution of CO2 to

global warming is increasing rapidly. We therefore

measured CO2 emissions as a proxy for GHG

emissions. The energy consumption of all the

equipment used in a particular activity was

considered for carbon emission calculation of that

activity. The energy consumed in liters of fuel or

kilo watt hour of electricity was converted into

Kilograms of CO2 to calculate carbon emissions.

The conversion values used are based on the

National Atmospheric Emissions Inventory UK

(2003). These values are considered as standard

because they represent the emissions based on

burning of one unit of the fuel. Small differences

between values are found from country to country,

when specific factors such as efficiency of

equipment or working conditions are considered.

However, these differences were relatively minor

and were hence ignored.

Next, the CSM for each activity was analyzed. A

Future State Map (FSM) depicting a ‘Lean’ method

of executing the activity by minimizing the non-

value-added components was then evolved. Since

it was not practical to implement the FSM on site,

the ‘Lean’ future state was simulated using the

STROBOSCOPE environment. Stroboscope

(Martinez, 1996) is an acronym for State and

Resource Based Simulation of Construction

Processes. It is a programming language specifically

designed to model construction operations.

Stroboscope models are based on a network of

interconnected modeling elements and on a series

of programming statements that give the elements

unique behavior and control the simulation.

EZStrobe is an Interface between the general

drawing software Microsoft Visio and Stroboscope.

The FSM process was modeled in EZStrobe and

simulated in stroboscope. Simulation in this study

was done for each activity to analyze if the proposed

improvements in the future state are possible.

Hence simulation validated the future state maps.

A carbon emission calculation was then performed

for the simulated FSM. The carbon emissions in

the current and future state were then compared

to assess whether the use of ‘Lean’ construction

techniques led to reduced emissions, and in turn,

greater sustainability. This exercise was repeated


for all the five selected activities, and the results

were compared.

In the next section we present our results. A detailed

analysis for the first activity – Piling is shown. We

then present our results for the four other activities.

RESULTS

Piling Work

On one of our sites, we observed piling rigs

performing auger boring. Around 2600 piles were

scheduled to be bored into the ground. The

installation or construction of pile foundations

is generally associated with an enormous number

of problems, relating to subsurface obstacles, lack

of contractor experience, site planning difficulties,

lack of experience in adjusting the pile axis, length,

and size, problems due to site restrictions and

disposal of excavated spoils. These have a major

inf luence on productivity. The rate of steel

installation and pouring concrete is also impacted

by the experience of the steel crew and method

of pouring. All these problems greatly affect the

production of concrete piles on site.

A. Preparing The Current State Map

The process of installing Piles on site was as follows:

After surveying and adjusting the piling machine

on the pile axis, soil auger boring was done through

soft and weathered rock until the hard rock layer.

A core borer was then used to shape the bored

hole and a Bentonite Film coating was applied.

A reinforcement cage was then lowered in and

Bentonite was flushed out using a Tremmie pipe.

The concreting was then completed and the casing

was removed. Fig. 1 below represents this process

using a Current State Map with standardized VSM

symbols.

In the CSM, a special symbol - - is used to

show emissions in the process. Once this process

was completed, each of the sub-activities in the

Piling process was analyzed to see if the manner

in which they were executed contributed to any

of the 7 different kinds of wastes as described in

the ‘Lean’ management literature. Furthermore,

each activity was classified as a Value-Adding (VA)

or as a Non-Value Adding (NVA) activity. The result

of this analysis is shown in Table 1.

To illustrate this analysis with an example, the

activity of checking depth is categorized as a non-

value-adding activity since it does not directly lead

to the installation of the pile. In addition, it is

categorized as showing extra-processing waste

because the pile rigs already have electronic set-

ups which show the depth of driving and other

characteristics. In spite of this, the on-site personnel

conducted manual depth measurements as they

felt that the electronic data could be susceptible

to errors due to the vibrations of the machine.

On the other hand, the soil auger boring till the

soft disintegrated rock was considered to be a value-

adding activity that did not involve any type of

waste.

B. Optimizing The Current State And PreparingThe Future State

Once the activities were observed on site and

classified in this manner, analysis was done on

ways to reduce wastes and NVA activities. Based

on the issues pertaining to the site that we observed,

we were able to arrive at 5 interventions to reduce

wastes and optimize the process. These were:

1. Improving the accuracy of the survey

measurements to ensure that the pile rigs

do not wait unnecessarily

2. Performing surface leveling to better align

the equipment and reduce the time required

for alignment

3. Improving procurement planning to ensure

that concrete and Bentonite are mobilized

in a timely manner


Figu

re 1

: C

urre

nt S

tate

Map

Of

The

Pili

ng P

roce

ss


4. Improving site planning to minimize travel

time

5. Minimizing the delays in removing the

casing

It must be noted that these interventions can vary

from site to site, and independent analysis must

be carried out in each instance.

These interventions led to a Lean process, where

wastes and time spent on non-value-adding activities

was greatly reduced. The optimized 'Lean' process

is represented in the Future State Map in Fig. 2.

C. Simulating The Future State

Based on our interventions, the future state was

then simulated as a means to validate the accuracy

of the proposed future state map. When practical

implementation is difficult, simulation can be used

to show that our assumptions on the rate of

Table 1 : Waste And Value Categorization Of Piling Activities

improvements are true. The future state with

proposed improvements was modeled in EZStrobe

and simulated. The simulation results show the

number of iterations in the queues, the activities

and the average durations. Fig. 3 shows the model

built in EZ-Strobe (i.e the sequence of activities

that were modeled), while Table 2 shows the results

of the simulations.

The simulation performs multiple iterations to

arrive at the duration of the activities in the piling

process, given the process and resource constraints

that are provided as inputs. The constraints reflect

the resource availability at site, while the process

incorporates the ‘Lean’ modifications generated

through the Value Stream Mapping exercise. The

simulation indicates that the overall activity

duration can be reduced as a result of incorporating


Figu

re 2

: F

utur

e St

ate

Map

Of

The

Pili

ng P

roce

ss


‘Lean’ construction principles and provides values

for the durations of sub-activities that are then

re-integrated into the future state to arrive at a

project duration. This duration represents the

simulated time taken to perform the activity (its

Future State), after ‘Lean’ construction principles

have been introduced.

D. Carbon Footprint Calculations

Once the current and future states were determined,

we performed Carbon footprint calculations for

each of these states to determine the difference

in carbon emissions prior to using Lean

Construction principles and after Value Stream

Optimization was performed. We considered only

construction equipment emissions as a proxy for

carbon footprint calculation. Material embodied

energy or energy consumption of small electrical

appliances such as bulbs etc. were not considered.

The value stream maps show the sources of carbon

emissions. The emissions are calculated based on

the equipment’s energy consumption and its

working hours. These emissions are then converted

to Kgs of CO2 using conversion factors. The

working hours for the current and future state are

obtained from the mapping done earlier. The energy

consumption data was obtained from semi-

structured interviews with the Plant and Machinery

departments of the site. The difference between

the carbon footprint of the current and future states

arises due to the difference in working hours in

both cases. This difference arises due to the

elimination of wasteful working of the equipment

(e.g excess traveling or waiting while being switched

on) through the use of Lean principles. Our results

are shown in Table 3.

Table 4 summarizes the changes in productivity

and carbon emissions due to the implementation

Figure 3 : EZStrobe Model Of The Piling Process


Table 2 : Simulation Results

of Lean Construction Practices for the Piling

Activity. As the table indicates, 'Lean' techniques

led to both productivity improvement as well as

reduction in carbon emissions.

E. Results For Other Activities

The same procedure described above was carried

out for the other four activities - open foundation

construction, slab concreting, block work and

structural steel fabrication. Given the large amount

of detail for each case, and the similarity of the

research methodology used, we present a summary

of our findings for all five activities in Table 5.

(Details with regard to reductions in carbon emissions

and cycle times for the other four activities are given

in the Appendix 1 - 4).

DISCUSSION AND CONCLUSIONSOur results indicate that in all 5 cases, the use of

Lean Construction practices resulted in productivity

improvements as well as carbon emission reduction.

Our exploratory study therefore indicates that ‘Lean’

is indeed ‘Green’.

Comparing between activities, it appears that the

sustainability benefits to undertaking ‘Lean’

construction are highest for Open Foundation

construction, followed by block work and piling.

Carbon emission reductions were rather minimal

for slab concreting and steel fabrication. However,

the cycle time reduction through the use of Lean

techniques was highest for Block work, followed

by Slab Concreting and Piling. Productivity


improvements were relatively smaller in the case

of steel fabrication and open foundation

construction.

While observing the reduction of wastes across

activities, we observed that the pre-eminent waste

categories across activities were Transport and

Waiting waste. Transportation waste has the largest

and most direct impact on the environmental

footprint. Most activities involved considerable

amount of transportation of materials and

movement of equipment, as well as idling of

resources. Much of this was wasteful. In retrospect,

this finding was not very surprising given the

equipment-intensive nature of these activities.

From a practitioner’s perspective, our study provides

support for the fact that ‘Lean’ practices can

improve sustainability on site. Furthermore, if the

objective is to maximize site sustainability, then

Lean techniques should be implemented in

Foundation, Piling and Block work activities to

start with. In trying to combine both cycle time

reduction and reduced carbon emissions, Block

work, and to some extent, piling, yield the highest

joint benefits, while both productivity

enhancement and emission reduction are relatively

negligible in structural steel fabrication. These

findings provide practitioners with some insights

on which activities could provide the highest ‘Lean’

and ‘Green’ benefits, and where to start when

contemplating ‘Lean’ implementation on site.

From an academic perspective, this study provides

further support to earlier studies that show the

Table 4 : Summary Of Results For Piling

Table 3 : Carbon Emission Reductions From Rquipment Use In Piling


sustainability-related benefits of ‘Lean’

Construction. In addition, this study extends prior

work in this area by showing that the positive

relationship between ‘Lean’ and sustainability is

valid in the Indian construction context as well.

However, there is more work to be done. Other

kinds of activities can also be analyzed to see if

our findings can be generalized across civil,

mechanical and electrical disciplines in

construction. We have used only one Lean

technique – Value Stream Mapping. Several other

‘Lean’ techniques exist. Future studies can apply

these other ‘Lean’ techniques, in isolation or in

combination, to see if there are significant changes

in productivity or sustainability outcomes. Finally,

our results can be rigorously validated through

employing statistical techniques on data obtained

from large numbers of observations for a particular

activity.

This paper set out to explore the relationship

between ‘Lean’ Construction and sustainability.

Through using the Value Stream Mapping

technique from the ‘Lean’ Construction literature

we were able to optimize the process of execution

of 5 types of activities. We were able to then calculate

the change in carbon emissions due to this

optimization, for each activity. While our study

is exploratory, our results unequivocally show that

‘Lean’ is indeed ‘Green’. We encourage

Table 5 : Summary Of Results From Our Study

practitioners to adopt ‘Lean’ techniques in their

construction processes, and researchers to join us

in studying the outcomes of these interventions.

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Appendix 1: Open Foundations

Table 1a : Carbon Emission Reductions From Equipment Use In Open Foundations

Table 1b: Summary Of Results For Open Foundations

Appendix 2: Slab Concreting

Table 2a : Carbon Emission Reductions From Equipment Use In Slab Concreting


Table 2b : Summary Of Results For Slab Concreting

Appendix 3 : Blockwork

Table 3a : Carbon Emission Reductions From Equipment Use In Blockwork

Table 3b : Summary Of Results For Blockwork

Appendix 4 : Structural Steel Work

Table 4a : Carbon Emission Reductions From Equipment And Material Use In Structural Steel Work

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