cost of co2 reduction in building construction

Pergamon 0360-5442(94)00084-0

Energy Vol. 20, No. 6, pp. 531-547, 1995 Copyright © 1995 Elsevier Science Ltd

Printed in Great Britain. All rights reserved 0360-5442/95 $9.50 + 0.00

COST OF CO2 REDUCTION IN BUILDING CONSTRUCTION

PIYUSH TIWARI and JYOTI PARIKHt Indira Gandhi Institute of Development Research, Gen. Vaidya Marg. Goregaon (East), Bombay-400 065,

India

(Received 7 April 1994; received for publication 28 November 1994)

Abstract--The construction sector accounts for the highest share (17%) of CO2 emissions by final demand in the Indian economy because it uses highly energy-intensive materials and the need for shelters is very high. This sector is highly vulnerable to changes in pricing structure. Various construction techniques have been analysed and it is shown that a room of length 3.5 m, breadth 3.5 m and height 3.14 m would lead to about 6 tonnes of CO2 emissions if constructed at the minimum possible cost. These costs are distributed as follows: foundation--25%, walls---46%, roof--16%, floor--4.8%, and plastering--8.6%. If cement is replaced by lime, the cost of construction increases by 0.14% for a 3% reduction in emissions. Further reduction in emissions is achieved by using stone instead of bricks. The cost increases by 0.54% for a 4% reduction. However, for a 21% reduction, the cost escalates by 27%. We also examine impacts on employment, materials used etc., due to changes in techniques.

1. INTRODUCTION

The housing-stock shortage in India, as estimated by the Planning Commission, 1 is about 31 million units. This estimate does not consider the housing needs of the large segment of Indian consumers residing in the countryside. They have only huts (kachha houses) to live in. These huts are being rapidly replaced by "pucca" houses. These "pucca" houses use energy intensive construction materials such as bricks, cement, steel, glass, aluminlum, etc. CO2 emissions are associated with these energy usages. Cement, besides emissions related to energy consumption, has also process related CO2 emissions. Moreover, production capacities of these construction materials are often constrained by energy availability.

Sectoral CO2 emissions derived using an input-output approach for India and 1983-1984 data, show 2 that construction is the largest CO2-emitting sector by final demand with its share of 17.0% when direct and indirect emissions are considered. Direct CO2 emissions at the construction site are marginal because of minor applications of machineries that use fuels. A subsequent analysis by Parikh 3 using 1989-1990 input-output table showed similar results (see Fig. 1).

Other papers 4-1° on CO2 emissions and energy consumption using the input--output approach for developed countries also show that building materials like cement, bricks, tiles, refractories, etc., have high direct and indirect energy intensities. The proportion of the total output of different materials going into construction is shown in Appendix 1. The shares of materials used in the construction sector in the national total are: cementm86.4%, iron and steel--37.6%, coal tar products (used mainly in road construction) 49%, wood and wood productsm55%. A brief description of manufacturing processes and energy consumption of some construction materials is given in Appendix 2.

The questions addressed in this paper are: Is there any possibility of reducing the CO2 emissions in the construction sector? If yes, at what cost? With what techniques and materials? What are the impacts of alternative technologies on employment generated in construction? How does the cost increase? How do the construction techniques shift to minimise costs? Generally, less energy-intensive techniques are more labour-intensive. In a country like India, where cheap labour is available, less energy-intensive techniques will have the dual advantage of reducing construction-related CO2 emissions and generating employment. The paper also explores alternative construction activities to reduce CO2 emissions.

tTo whom all correspondence should be addressed. 531

532 Piyush Tiwari and Jyoti Parikh

21 --

19 --Construction .g .~ 17

E Is

o. / .oo ,°° .,o" , / e"

e L

3

1

T o p ten contr ibut ing sec tors (by f i n a l d e m a n d )

Fig. 1. Direct and indirect carbon emissions 1989-1990 (as a percentage of total carbon emissions). Source: Parikh. 2

2. MODEL FOR BUILDING CONSTRUCTION

Construction, as represented in the input-output table of India, is a very wide term comprising various construction activities such as houses, roads, bridges, tunnels, dams, structures related to irrigation, etc. However, only housing construction activity is considered in the paper. Moreover, only commonly used techniques are applied. Low-cost housing techniques such as mud-based techniques have not been included. The house, considered for analysis, is measured in units of a room of standard size (3.5 x 3.5 × 3.14 m3), as shown in Fig. 2.

A house may be assumed to be a combination of such rooms and it can exist anywhere in the building and have up to three floors. Up to three floors, the minimum wall thickness is one brick. Beyond this, the minimum wall thickness increases. ~1 However, in normal construction practices, the walls beyond the third floor are rarely load bearing. Generally, a framework of columns and beams is constructed which is load beating and the space in between is filled with non-load-bearing brick walls. The CO2 estimates for buildings above three floors will be underestimated since emissions due to columns are not accounted for. The idea of this paper is not to calculate emissions for a particular type of house

Minimum thickness of walls

B r i c k w a l l = 2 0 c m

sterne w a l l = 3 0 c m

Thickness of roof slab = 15 cm

/ Roof

Wall

: 3.5 m

Fig. 2. Room considered for analysis.

j! ~ r i - i

a

1

Cost of CO2 reduction 533

but to calculate emission intensities for different construction techniques. The CO2 emission intensities for different construction techniques have been defined as CO2 emissions in tonnes per room construction.

Chenery ~2 described a methodology for including engineering variables in defining the production function. This idea has been used in Refs. 13-18 for various applications. An optimisation model similar to those of Narayana ~7 and Buttler et al ts is used. The engineering variables have been defined explicitly as in the Buttler model while retaining the feature of choice of techniques of the Narayana model. We include a constraint on CO2 emissions in this model.

The model identifies a combination of methods at different stages of construction (viz., foundation, wall, etc., as defined below) to meet optimal levels for various activities required at each stage of construction of the structure, subject to specified objectives and engineering and economic constraints. The model has two types of activities: activities related to primary resources required to produce the intermediate inputs to be used for construction of the structure and activities related to various techno- logical alternatives of construction of each stage of the building. Primary resources include fuel (electricity, coal), limestone, gypsum, etc. (Appendix 3) which are required in the production of cement, bricks, lime, steel, etc. (Appendix 3). Figure 3 illustrates the direct and indirect inputs in building construction. The indirect inputs (primary inputs) are raw materials into intermediate inputs that are directly used in building construction.

In this model, different technical specifications that provide the same outputs are considered. The levels of resources and production activities are determined so that the overall cost of construction of the specified room is minimum. The notations for different sets appearing in this model are: p is the set of primary inputs (p = l -P) ; i is the set of intermediate inputs (i = 1-I); j is the set of production- activity levels (j = l -J ) ; q is the set of different wage classes (q = l -Q); and g is a set of different stages in construction (g = I-G).

The stages of construction considered are: stage 1 foundation bed under load bearing wall; stage 2 foundation bed under partition wall; stage 3--foundation for load bearing wall; stage 4 foundation for partition wall; stage 5--wall construction; stage 6--partition wall construction; stage 7--roof construction; stage 8--flooring; stage 9-----external plastering; stage 10---internal plastering. A modelling framework "HOPE" (Housing options evaluation)" has been developed to determine the quantities of materials required for the building. Model equations are given below:

Primary inputs

Einc Coal Coarse Pine Stone at Coal Coal Stone Stone Coal Coal Clay sand send quarry Lime Clay at at Iron Lime Sand Coarse quarry quarry ore Gypsum sand Mg Clay ore Water Dolomite

Sand atone

Cement Brick Coarse Fine sand Stone aSg. Unslaked Surkhi Stone at Through Steel sand l lme quarry stones

Intermediate inputs

Sand storm

EGY 20-6-E

Building construction

Fig. 3. Direct and indirect materials inputs in building construction.


2.1. Objective funct ion

We minimise

cost = E E c,a~j + g E wqd#,, i j q j

intermediate direct + inputs labour

(1)

where c~(i = 1,I) is the cost coefficient for the ith intermediate input corresponding to the ith activity and Wq(q = 1,Q) is the wage rate for the qth class of labour. The requirement for the ith intermediate input to produce unit output of the jth activity is given by element aij(i = 1,I; j = 1,J). xj(j = 1,J) is the level of the production techniques, dqj is the qth type of labour employed directly for unit production level of activity j. The matrices a o and dqj, have been compiled from Chakraborty ~9 and CPWD. 2° The primary input prices for the year 1989 are taken from CSO. 2~ CPWD 2° gives the prices of intermediate inputs and labour wages for different classes in 1989.

2.2. Resource constraint

If N s is the number of alternative techniques available at stage g, the total number of techniques available is

N=•Ng. (2) g

All levels of activities from G stages taken together are represented as

(xl,x2,..Jcj,. . .xn)=X'. (3)

A list of xj is given in Appendix 4. a o is the requirement of intermediate inputs to produce unit output of j th activity, i.e.

Intermediate input

E a i j x j ~ r~ . J

requirements ~< availability

(4)

The element ri(i = 1,I) is the total amount of the ith intermediate input required to run the production activity at a level X. The element bp~ gives the requirement of the pth primary input to produce unit output of the ith intermediate input (p -- 1,P, and i = 1,I), i.e.

Primary inputs

~bpir , <~ tp , i

requirements ~< availability

(5)

where tp(p = 1,P) is the total amount of the pth primary inputs required to produce the intermediate inputs ri Combining Eqs. (4) and (5) yields

Primary inputs

t, >- Y. gbp,,,,,x,. i )

availability ~> requirement

(6)


2.3. Direct, indirect and total employment

In the present model, six types of labour have been considered (Appendix 5) with their wage rates, d~ is the qth type of direct labour required for the jth activity. Sqi are the indirect labour requirements of the qth earning class to produce the ith intermediate input. The indirect labour requirement for each wage class is

Indirect labour

Z Sqiaij ~ lqi , i

requirement ~< availability

(7)

where lq~ is the qth type of labour required to produce the ith intermediate input. The total aggregate employment (not by labour class) is

~] (lqj + dq~) xj. (8) q )

2.4. Output constraint

The task level for every stage of building a room varies with the choice of the technique of construction. For example, to support the same load, the thickness of a stone wall should be more than that of a brick wall. The type and quantity of materials required change according to principles of structural engineering. The material requirement at every stage is a polynomial function of the area and height of the building. 18 The output constraint is

Z Z j g X j ~ y g . J

output <~ task level

(9)

The element Zig represents the output coefficient of the jth activity at stage g. yg is the task level for each stage.

2.5. Engineering constraints

In building construction, the choice of techniques for one stage is not entirely independent of the choice of techniques for other stages. These interdependencies and internal balances in production have to be taken care of. These engineering constraints are written as

u 0 x 0 ~ 0. (10)

To understand this constraint, it is necessary to explain how the u 0 are derived. Consider two activities x~ and xz corresponding to stages 1 and 2, respectively. Let 1 correspond to the foundation and 2 to the superstructure wall. Now, if the wall is constructed by using technique x2i, it is required that the foundation is built only by using x o. This constraint is introduced as follows. Let x2 = superstructure wall work in m 3 built by using technique x2i, and x~ = foundation work in m 3 built by using technique xij. As the dimensional details of both wall and foundation are known from engineering calculations (see Sec. 2), the lengths for which Xl and x2 are built are calculated by multiplying their levels by proper constants.

If k~x] is the length for which the foundation is built by using x 0 and k23¢2 the length for which the wall is built by technique XEj, then x2 depends only on x~, so that k~x~ should be at least equal to k2x2, i.e.

k i x ] - k 2 x 2 >I 0 or Xl -- (kz/kl)x2 >! O. ( 11 )

The coefficients of xi and x~ become the uij.


2.6. Environmental constraints

In this model, the environmental constraints appear as

~ t p Ep ~ TC. P

C02 emissions ~ upper limit on C02

(12)

Only indirect CO2 emissions due to production of primary inputs are considered. Ep is a vector of the CO2 emission-coefficients for p primary inputs. The total requirements of p primary inputs to meet the levels of intermediate-input requirements are calculated. When multiplied by emission coefficients associated with each of the p primary inputs and aggregated over p, we find the total CO2 emissions related to construction. TC is the upper limit on CO2 emissions.

2.Z Non-negativity constraint

To restrict the choice variables to positive values, the following constraints are applied:

tp > /0 and x s >I O. (13)

3. DISCUSSION OF RESULTS

A base-case model solution is obtained by minimising materials and labour costs without environmen- hal constraint. This base case may still be better than "common practice" (referred to as CP) because the base case chooses sometimes lime-based techniques. In practice, cement-based techniques are used which are relatively more energy-intensive. One can estimate approximately the cost and materials required for this case. The CP case, as obtained from the model, excludes lime-based techniques. The results may still be an underestimation of the actual CP case since the optimisation model is used even for this technique. Table 1 summarizes the comparison between the CP and the base cases. The cost of construction in the CP case is about 145 Rupees higher than for the base case. The CO2 emissions for the CP case as modelled are about 6.25 tonnes compared to 5.88 tonnes for the base case. The cement used in the CP case is 2.23 tonnes compared to 1.60 tonnes for the base case. The base case uses more lime (about 787 kg) compared to the 220 kg in the CP case. Comparisons for other materials are also shown in Table 1. A comparison of techniques used at different stages is shown in Table 2. There is a difference in the techniques used at the foundation and wall levels.

Figure 4 shows the shares of different stages in CO2 emissions. The shares of different stages in total CO2 emissions are: walls--46%; roof--16%; foundation bed--15%; foundation--9.9%.

The model is run with 3, 4, 18, and 21% CO2 reductions below the base case. These levels are

Table 1. Comparison between the CP and the base case.

c_~__ ot co~ructi~ (a~.)

CO~ r~'_,~_'_~(tor, ffis)

C.offimm.d(m')

Free und(m +)

Sto~ ~ S a ~ m ' )

U - ~ l . ~ iime.(cptl.)

s t ~ l ~ s )

S ~ m ' )

~ c a J e ~ a u ~

7561.52 74t?.4

6.02 6.02

5.71 2.75

1.64 1.93

5.49 5,50

0.22 7.87

66.39 66A7

2A


Table 2. Comparison of techniques in the CP and the base case.

Sta~,s

Fmmdmim bed under load bming wall

~oundatim bed unda pmi~a wall

Foundatioa for lind t ,m'~ wan

¥oudation for pm.tlthm

bem'inl wall

Partitiou wall

Roof

Floor

~nta'ud Pteste~

External Plulm'in8

C P ~

1:4:8 Cement

1:4:8 C_.ement Couceeie

1:1:8 Cement,sand, lime trickwc~

1:6 cement, coarse sand brickwork

1:6 cement, coarse sand brickwee'k

1:6 cement, coarse sand brickwork

1:3:6 RCC balenced

40ram 1.'2:4 cement coacle~ floor

12ram 1:6 cement mortar

12ram 1.'6 cement inottez

]~ute gllse

1:4:8 Cement ~ m e l e

1:4:8 Cement Coacge, te

1:1:8 cement, sand, time bikkwotk

1:1:8 cem~t, mad lime brickwork

1:2 I~e , surkhi brickwork

1:2 lime, surkhi briekwork

1:3:6 RCC balanced

40ram 1".2:4 cement coacrete floor

12ram 1:6 cement mortar

12ram 1:6 cement

9.86q~

46.04~

15.67%

Legend

Foundation bed ~ Vound.~o~

i w , n , ~ R o o f

Fig. 4. Shares of different stages in total carbon dioxide emissions for the base case.

chosen because these are associated with complete replacement of some techniques to reduce CO2. Figure 5 presents an isoquant for construction of this specified room.

The output, i.e. space enclosed by the room, is fixed and there is a trade-off between cost and CO2 emissions associated with construction of this room, as shown in Fig. 5. The changes in techniques associated with reductions in CO2 emissions are listed in Fig. 6. Up to 3% emission reduction can be achieved by replacing a 12 ram, 1:6 cement mortar technique for internal plastering by a 12 ram, l : l : l lime, surkhi and sand mortar. However, when a 4% reduction is desired, the cost increases and substitution techniques are needed for the foundation under the partition walls, the foundation under the load-

538 PiyushTiwar iand Jyoti Parikh

O

1 1 , 0 0 0 -

1 0 , 5 0 0 -

1 0 , 0 0 0 -

9 5 0 0 -

9 0 0 0 -

8 5 0 0 - -

SOO0 - -

7 5 0 0 - -

7OO0 4 .0

\ ~'s ' i .~s.

I t i "II "ll

O.

B4 m " I

*00.B M.M.I

I I I l l 4.5 S.O 5.5 6 .0 6.5

E m i s s i o n s ( t o n n e s o f C O 2 )

Fig. 5. Isoquant for construction of a room.

Stages D u e C u e

Foendatim bed fat k=d beeries weU Foeadafim bed uadet ~ ~ieon wan Foeadattaa m d ~ the k ~ l - b e a ~ wan

Foeadatim tmd~ the vana~ wen

Loed-beadng

Pmlifioa walls

Roof Floor

Examud ph=teang

]nter~ plu~'iag

1:4:8 Cemeat Cea~ete

1:4:8 Cmteat

1:1:8 ~a~at . time.s~ Ixickwetk

1:!:8 ~neat , lime,,m~ brickwetk 1:2 lime, mflflfi Ixlck nk~aary

l:21ime, ma'khi l~ckmamawj

1:3:6R.C.C 40ram 1".2:4 ta lent floor

12mm 1:6 g e m ~ l a m l f

Up to 3~ co,

.

Up to 4~ COa Up to 18% Up to 21~ ~ e c a m c o , co ,

1:1:1 lme. Sur~. laad btktwelk

l:l:llime.

5tkkwerk

1:1:1 lime, ~ch i . aad btkkwetk

12nun 1:6 12mm 12mm 1:1:1 eemmtmettm" l:l:llime, Umo, surkbi,

mad immr mad

1:1:1 m~d~. mKI br~-wod~

1:1:1 ~-ud. md I~kkv~'k 1:1:1 lime, ~ d , ~ sand nmdom

12mm 1:2:9 cemeat m ~

12mm 1:1:! lime, turin. rand momx

1:1:1

1:1:1

1:1:1 lime,, autdli, mad

: random mat~w~tk

1:1:1 lime,,

1:5 cemem

1 ~nlan 1:2:9

I N 1:1:1

Fig. 6. Changes in techniques for different cases of emission reduction choices.

bearing walls, and the load-bearing masonry wall, along with internal plastering (Fig. 6). After a 4% reduction, there is a linear increase in the cost of construction (Fig. 5) because brick masonry is being replaced by stone masonry. After this, there is a drastic change in technique for almost all stages as shown in Fig. 6.

The trend of substitution continues until 21% of CO2 reduction is achieved with the present set of techniques, but the cost increases. Four cases with total changes in technique of construction for one


or more stages have been discussed. All changes in technique, materials, employment, etc., are compared with the base case and discussed below.

3.1. Costs of various inputs

The percentage distribution of construction expenditures incurred for different construction materials is as follows: bricks--10%; cement 9%; iron and steel---7%; labour and service charges 40% (Appendix 6). These taken together account for 66% of the total cost. Table 3 indicates that with the reduction in CO2 emissions, the cost rises.

The reduction in CO2 emissions by 3.0% increases the total cost by 0.14%, the intermediate inputs bill by 0.07%, the direct wage bill by 0.36%, the indirect wage bill by 5.38%, and decreases the primary bill by 2.25%. This trend continues with varying magnitudes of changes until another 1% reduction in CO2 emissions is achieved. Beyond this level, there is a sharp increase of 19.33% in cost for a reduction of 18.0% in CO2 emissions, as indicated in Fig. 6. There is sharp increase of 23.2% in the primary input cost, which was decreasing till a 4% reduction in CO2 emissions. The rest of the cost components follow the same sign obtained earlier but the increase occurs in a non-linear fashion. The trend continues to a 21% reduction in CO2 emissions, beyond which it is not possible to reduce CO2 further.

3.2. Level of production activities

The levels of activities are summarized in Table 4. As the CO2 emissions constraint is made more stringent, the tendency is to choose activities at different stages that use less cement. The cement is substituted by lime that has less CO2 emissions attached to it. This trend continues to a 4% CO2 emissions reduction. After this, the use of bricks decreases by replacing brick masonry by stone masonry and the brickwork foundation by a stonework foundation, along with substitution of cement by lime.

The changes in techniques occur at stages 3, 4, 5, 6, 8, 9, and 10 (Fig. 6). In stage 3, as CO2 is reduced, lime-based techniques are chosen along with stonework. There is no change in technique for stage 4 till a reduction of 3.0% in CO2 emissions. After that, brickwork using lime mortar is chosen. At stage 5, we also choose brickwork using lime as mortar, thereby reducing the consumption of surkhi, because surkhi requires burning of coal for its production (Appendix 2). However, these techniques are costly and increase the intermediate inputs bill. Stage 6 also follows a brick masonry technique using more lime and less surkhi. Till 20% CO2 emissions reduction, the floor type is 40 mm thick 1:2:4 cement concrete floor. However, when 21.0% CO2 emissions reduction criteria are imposed the choice is sandstone flooring. The internal and external plastering techniques also substitute lime for cement.

3.3. Intermediate inputs requirements

The above discussions conclude that the trend of choice of techniques is to reduce the use of bricks, cement and surkhi. In most of the stages the brickwork is replaced by stonework. The choices of

Table 3. Cost of various inputs under different scenerios.

Objective value(Its.)

latmmsdiate input bin(Rs)

l'rtmm: inpue bin0ts.)

ln4~rect wagd~mfP.s.)

Direct wagebm(~)

Total wa~iU(~)

Base Case

7417.4

5625.3

1814.7

1281.1

1792.1

3073.2

3% change ova" I ~

0.14% inc~ase

0.07% incTease

2.24% decteue

5.38% inc~ase

0.36% incxease

2.51% im=eme

4% chaage ove¢ l~e

0.54%

0..34% income

1.74% cleev~.....~

6.87%

1.17% in~rease

3.63%

18% clump

over hue

19.33% increase

20.25% increase

23.2% in.cue

28.93% increue

16.28% incaease

22.07% in.ease

21% dmge

ova hae

26.74% in.ease

24.7% in~t~.._se

35.77% in,ease

29.15% increase

32.6% increase

31.20% increase


Table 4. Levels of production activities.

Su~,t

S ~

e..e C,m 0~o eo,

Teclnkl.e

Xl (ram)

X4 (am,)

X13 (ore)

X~2 (ran)

SUIIeS X46 (om)

SuqI~ X6S (~.,,)

suje7 x~ ( m )

xv4

x'~ (s~ )

s~e]o x ~ (s~ )

cum = cubic meter; sqm = square meter.

Smlmlo I O'5 (30, mdmkn)

Level Tedmigm l.md

132 Xl(,'-m) 1.12

Z.m ~ X4(mn) 2-O3

1.07 Xl~mm) 1.07

!.07 X32(mn) 0.30 X3.4(mm) 0.78

4.95 X,,~am) 4.95

4.95 X~(cm) 4.95

12.25 X'~(~lm) 12.25

12.25 X74CSqm) 12.25

,U.~5 X83(Sqn) ,n.~

4:).~ XS4(Sqm) 4~.5~

s o r e 2 (4'Jr CO. e..,', _,.',~_~

TedmSqm Lwd

Xl (ram) :132

X4 ( ~ ) 2.03

XlS(mn) 1.07

X:~Kcm) 1.O7

X 4 5 ( ~ ) i.91 X~(~m) 3.0S

X ~ ( ~ ) 4.95

i XT~m) 12.7.5

xv4(sqm) 12.25

XS,WSqm) 43.96

x84(Sqm) 43.~

s o ~ $ (lS~ (x)s ~ )

Tedmkim

Xt(om) !.32

X4(mm)

XtS(mn) 1.07

X~4(mn) 1.07

X~(mn) 0.01 X53(ma) 6,6O

X~cm) 4.9J

~ ) t2.~

X'/4(S~) 12aa

xs3(~m) 43.96

x~(,qm) 4~.~

szmedo 4 t2t~ co, ~ )

Tedmuk~ Level

Xt(om) l~O

X4(,:,m) 2.m

XlS(ma) 0.3# x23(,--,) 0.~

X)4(mm) ]a7

XSl(mm) 6.6O

X64(cum) 4.95

I XT~Sqm) 12.7.5

X77(~) t2aS

Xln(,qm) 43.~

! X U ( ~ ) 43.96

stonework is associated with increased consumption of lime and stone but it reduces the brick consumption substantially. The surkhi consumption decreases from 2.4 cum to 1.85 cum. The consumption of various intermediate inputs under different cases of CO2 is tabulated in Table 5.

Figure 7 shows the trade offs between different building materials. As stringent conditions are imposed on emissions, the use of cement decreases and lime increases.

For 5% onwards reduction in emissions over base case, the bricks are replaced by stones. The thickness of stone wall to withstand the same load is more. Hence, the surface area of joints increases and this increases the requirements of cementing materials (cement, lime, etc.). The model, however, chooses lime.

Table 5. Intermediate inputs requirements.

Inputs

Cema~ (tom)

Bricks (thons)

coenc Sand (,i,')

Fi~e Sand tin')

Stone agpepte (ms)

Unslaked t.~ae(qn~

Sur~ (m')

Stone at qumy(m3)

Thrash stmes(nm.)

Sand stone(sqm)

Steel (kS)

Base Cue

1.60

6.02

2.75

1.93

5.50

7.87

2.40

66.40

3% co , reduction

1.40

6.02

2.84

1.35

5.50

1020

2.47

66A7

4~t co , reduction

1~34

6~2

3.23

0.98

5.50

10.93

2.40

66.40

18~t (x~ reduction

1.30

3..54

3.00

2.02

5.50

14.77

2.48

8.24

46.0

66.39

21~ CO z reduction

1.24

3.18

3.70

2.07

5.26

14.52

1.85

9.18

53.0

12.25

66.39

Cost of C02 reduction 541

Legend

Cemeat (quintals) + Lime (quintals) 0 Brick (thousand) A Stone (cubic m.)

17 - 16 15 14 13 12 11 10 9 S 7 6 S 4 3 2 1 0

4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8

Emissions (tonnes of CO2)

Fig. 7. Tradeoffs between major construction materials.

3.4. Primary inputs requirements

The policy for reduction of CO2 emissions involves reduction in coal consumption. This is achieved through reduction in bricks consumption. But substitution of brickwork by stonework involves high consumption of stone and lime. Gypsum consumption decreases marginally because it is an input to cement. Clay, which is an essential input to brick manufacturing, also reduces. Quarry stone consumption increases with more and more choice of stonework. Electricity is used only for manufacturing cement. With decrease in cement consumption electricity consumption also decreases. This is tabulated in Table 6.

Table 6. Primary inputs requirements.

Inpum s u e 3~, cOa 4~, cos tS's Cos 2 t~ cOs c u e mdacltm maaclioa nldaclulm

t

c o ~ Sad ~m~ 3..SS 3 ~ 4 ~ 3.53 4.16

Stud(re') 1.93 1.35 O.98 2.0~ 2.07

Qmay Smae(mP) 6.O4 6.04 6.O4 ]S.S6 16.71

Cod (mares) 2.18 2.19 2.19 1.80 1.7

OcW~) 191.5 168.1 161.03 1.54.9 148.3

Lkz~oac Omm) "3.91 4.05 4.10 4.74 4.61

Gyimm (manes) 0.08 0.07 0.07 0.07 0.07

CI~ (maam) 35.35 35.52 3.5.36 23,40 ~0.13

W/.." (manes) 4.79 4.20 4.03 3.90 3.71

IJronore(mmmm) 0.13 0.13 0.13 0.13 0.13

Delomin(mnm 0.01 0~)1 0~1 0.01 0.01

Sand ~ s q . m ) ~ 13..50

l~4~mmm Ore 0.01 0.01 0.01 0.01 0.01 (mmm)


2OO

190

180

I 170 o r. ~, 160 -

o 150 - ,,D

140 - -

130 - -

\ I Il'll,m~ %

I'll~l I

"1 *l . i

"O4i

IQIIo.I. I

12o I I I I I 4.0 4.5 5.0 5.5 6.0 6.5

Emiss ions (tonnes of CO 2)

Fig. 8, Labour employed in construction of a room.

3.5. Employment

The total (direct and indirect) employment generated due to construction is plotted against tonnes of CO2 emitted. This is shown in Fig. 8. With reduction in emissions the employment (person-days) increases because the techniques that are chosen, such as stone based techniques, are more labour intensive.

The direct and indirect employment generation in person-days for different wage classes is tabulated in Table 7. With more and more labour intensive techniques being used the labour requirement in lower wageclasses increases.

4. CONCLUDING REMARKS

The construction sector uses energy intensive materials such as bricks, cement, non-metallic mineral products, iron and steel, etc., and accounts for the largest CO2 emissions by final demand in the Indian economy. The questions that arise are: What are the choices in reducing CO2 emissions in the construction sector? What are their implications in terms of costs, employment and other materials? The present paper analyses various techniques to construct a room of size 3.5 x 3.5 × 3.14 m 3. The alternatives compared, satisfy the same engineering criterion for the same usage.

Base Case

3~ CO, reduction

4~ CO~ reduction

18% C02 reduction

21% CO z reduction

Type of labour

Direct

Indirect

Direct

Direct

Direct

Indirect

Direct

Table 7. Level of employment (person-days).

Wageclml 1 Wageclass2 Wageclass5 ( ~ . 0-20) ~s.21-24) 0~>50)

36.1

45.4

36.4

48.4

36.3

49.3

44.7

72,4

53.3

73.7

7.5

6.2

7.6

6.2

8.2

6.2

9.2

3.9

10JS

3.5

W~eclus3 W~,eclms4 (l~s.~-30) (Rt30-35)

13.7

1,4 3.5

13.7

1.8 3.6

13.7

1.9 3.6

20.4

2.5 3.1

26.3

2.5 2.9

12.5

1.0

12.5

1.0

12.5

1.0

10.4

0.9

13.9

0.8


The model results indicate that 5.88 tonnes of CO2 are emitted while constructing a room. The actual construction practice involves emissions of 6.25 tonnes. If some of the cement is replaced by lime there is a 3% reduction in CO2 emissions, but the cost of construction rises by 0.14% even if all the inputs are priced as present. The 4% reduction in CO2 emissions increases the cost by 0.54%. After this, the increase in cost is drastic and increases by 27% for 21% reduction in CO2 reduction. There is an increase in employment levels associated with these technologies. However, the future increase in wages is not considered here. The direct employment level in the lowest wageclass (Rs.0-20) increases from base case level of 36.1 person-days to 53.3 person-days for the case corresponding to 21% reduction in CO2. The indirect level of employment for the same two cases rises from 45.4 person-days to substantial 73.7 person-days. The trend is the same in other wage classes, though with varying magnitudes.

Acknowledgements--The authors are grateful to K. Parikh, N. S. S. Narayana, S. S. Penner and an anonymous referee for helpful comments and constructive suggestions throughout the work. We thank P. Pushpa for helping us in preparing the manuscript.

REFERENCES

1. Planning Commission, "Eighth Five Year Plan of India," New Delhi, India (1992). 2. J. Parikh and S. Gokarn, Global Environmental Change, September, 276 (1993). 3. J. Parikh, M. Panda, and S. Murthy, "CO2 Emissions by Income Groups in Urban and Rural India," mimeo,

Indira Gandhi Institute of Development Research, Bombay, India (1993). 4. L. Klein, "Interindustry Analysis of CO2 Emissions," mimeo, Philadelphia, U.S.A. (1993). 5. A. M. Strout, "Using Input-Output Tables to Estimate Indirect Energy Requirements," A collection of working

papers and memoranda prepared in 1975, mimeo, Boston, U.S.A. (1979). 6. R. A. Herendeen and C. W. Bullard III, "Energy Cost of Goods and Services, 1963 and 1967," Center for

Advanced Computation, University of Illinois, CAC document 171, Urbana, IL, U.S.A. (1974). 7. R. Edwards and A. Parikh, Energy Policy 6, 66 (1978). 8. J. E. Jankowski Jr., "Industrial Energy Demand and Conservation in Developing Countries", Resources for

the future, Center for Energy Policy Research, DP D-73A, Washington, DC, U.S.A. (1981). 9. D. Simpson and D. Smith, "Direct Energy Use in the U.S. Economy, 1967," Center for Advanced Computation,

CAC technical memo 39, University of Illinois, Urbana, IL, U.S.A. (1975). 10. C. A. Jenne and R. K. Cattell, Energy Econ. 5, 115 (1983). 11. P. N. Khanna, "Indian Practising Civil Engineers Handbook", New Delhi, India (1993). 12. H. B. Chenery, Q. J. Econ. Theory, 63, 507 (1949). 13. J. R. Marsden, J. Econ. Theory 9, 279 (1974). 14. D. I. Pearl and J. L. Enos, J. Indust. Econ. 24, 55 (1975). 15. R. M. Solow, "Some Recent Developments in the Theory of Production," in M. Brown (ed.) The Theory of

Empirical Analysis of Production, National Bureau of Economic Research, New York, U.S.A. 16. W. Soren, Economica 51, 401 (1984). 17. N. S. S. Narayana, "The Engineering Production Function and Choice of Techniques in Building and Road

Construction," PhD Thesis, ISI, New Delhi, India (1976). 18. H. J. Buttler and M. J. Beckmann, Econometrica 48, 201 (1980). 19. M. Chakraborti, "Estimating, Costing, Specification and Valuation in Civil Engineering," Calcutta, India

(1992). 20. Central Public Works Department (CPWD), "Delhi Schedule of Rates," New Delhi, India (1989). 21. Central Statistical Organisation (CSO), "Statistical Abstract of India," New Delhi, India (1989). 22. Sarvekhshana 15(3), Department of Statistics, New Delhi, India (1992).


APPENDIX 1

Percentage of Total Output Going into Construction. Source: Input-Output Table for Indian Economy, 1989-1990

Sectors % of total output

Jute, hemp, mesta textiles

Wood and wood products

Coal tar products

Other chemicals

Cement

Non metallic mineral products

Iron and Steel

Electric machinery

Electricity

Rail mmspon services

u-anspoa services

Trade

Other scrviccs

3.8

55.1

48.8

5.0

86.4

17.0

37.6

16.0

4.5

8.0

5.0

7.1

1.4

APPENDIX 2

Manufacturing Processes of Selected Construction Materials

Cement---Cement is manufactured either by a dry or a wet process and requires coal or electricity for burning of slurry. The slurry (chalk or clay plus water), in the case of wet process of cement manufacture, is burnt at 2800°F. The nodules called clinkers, are formed. These clinkers are ground to form cement. In dry process, the raw materials (limestone and shale) are air dried and after proper blending are sent to kilns. After burning they are ground to form cement. The electricity required to manufacture one tonne of cement is about 120 kWh and the coal requirement is about 0.33 tonnes per tonne of cement production. Surkhi---Clay is burnt at a prescribed temperature for production of surkhi. Coal required to produce lm a of surkhi is 0.031t. Lime Lime which is manufactured by burning of limestone (shells or kankar) in kilns requires 800°C of temperature to be maintained. A kiln holding about 5.4 cum of shells and 2.27 cum of coal produces quick lime nearly equal to shells. However, 9 cum. of kankar and 2.25 cum. of coal gives 11.25 cum of slaked lime. Bricks--The moulded clay is burnt in the kilns to form bricks. The stages in firing cycle are (i) smoking, (ii) preheating, (iii) firing, (iv) soaking and (v) cooling. The coal requirement for this is about 0.2 tonne per thousand bricks.

APPENDIX 3

List of Inputs

Pr imary Coarse sand Fine sand Quarry stone Coal Electricity Limestone

I n t e r m e d i a t e Cement Bricks Coarse sand Fine sand Stone aggregate Unslaked lime

Cost of C02 reduction 545

Gypsum Clay Water Iron ore Dolomite Sand stone Manganese ore

Surkhi Stone at quarry Through stone Sand stone Steel

APPENDIX 4

Techniques Considered

A4.1. Foundation bed under load bearing wall

×1 1:4:8 Cement concrete x2 1:3:6 Cement concrete x3 1:2:4 Cement concrete

A4.2. Foundation bed

×4 x5 x6 x7 x8 x9

under partition wall

1:4:8 Cement concrete 1:3:6 Cement concrete 1:2:4 Cement concrete 1:3 Cement, coarse sand brickwork 1:2 Cement, coarse sand brickwork 1:4 Cement, coarse sand brickwork

×10 1:6 Cement, coarse sand brickwork x l l 1:1:6 Cement, lime, sand brickwork ×12 1:2:9 Cement, lime, sand brickwork ×13 1:1:8 Cement, sand, lime brickwork ×14 1:1:3 Cement, sand, lime brickwork ×15 1:1:1 Lime, surkhi, sand brickwork ×16 1:2 Lime, surkhi brickwork ×17 1:4 Cement, sand coursed stonework x18 1:6 Cement, sand coursed stonework x19 1:4 Cement, sand random stonework ×20 1:6 Cement, sand random stonework ×21 1:1:1 Lime, surkhi, sand coursed stonework ×22 1:1:8 Cement, lime, sand coursed stonework ×23 1:1:1 Lime, surkhi, sand random stonework x24 1:1:8 Cement, lime, sand random stonework

A4.4. Foundation for partition wall

x26 1:3 Cement, coarse sand brickwork x27 1:2 Cement, coarse sand brickwork x28 1:4 Cement, coarse sand brickwork x29 1:6 Cement, coarse sand brickwork x30 1:1:6 Cement, lime, sand brickwork x31 1:2:9 Cement, lime, sand brickwork x32 1:1:8 Cement, sand, lime brickwork x33 1:1:3 Cement, sand, lime brickwork x34 1:1:1 Lime, surkhi, sand brickwork x35 1:2 Lime, surkhi brickwork


A4.5. Load bearing wall

x37 x38 x39 x40 x41 x42 x43 x44 x45 x46 x47 x48 x49 x50 x51 x52 x53 x54

1:3 Cement, coarse sand brickwork 1:2 Cement, coarse sand brickwork 1:4 Cement, coarse sand brickwork 1:6 Cement, coarse sand brickwork 1:1:6 Cement, lime, sand brickwork 1:2:9 Cement, lime, sand brickwork 1:1:8 Cement, sand, lime brickwork 1:I :3 Cement, sand, lime brickwork 1:1:1 Lime, surkhi, sand brickwork 1:2 Lime, surkhi brickwork 1:4 Cement, sand coursed stonework 1:6 Cement, sand coursed stonework 1:4 Cement, sand random stonework 1:6 Cement, sand random stonework 1:1:1 Lime, surkhi, sand coursed stonework 1:1:8 Cement, lime, sand coursed stonework 1:1:1 Lime, surkhi, sand random stonework 1:1:8 Cement, lime, sand random stonework

A4.6. Partition wall

x56 x57 x58 x59 x60 x61 x62 x63 x64 x65

1:3 Cement, coarse sand brickwork 1:2 Cement, coarse sand brickwork 1:4 Cement, coarse sand brickwork 1:6 Cement, coarse sand brickwork 1:1:6 Cement, lime, sand brickwork 1:2:9 Cement, lime, sand brickwork 1:1:8 Cement, sand, lime brickwork 1:1:3 Cement, sand, lime brickwork 1:1:1 Lime, surkhi, sand brickwork 1:2 Lime, surkhi brickwork

A4.Z Roof

x67 x68 x69 x70 x71 x72 x73

1:2:4 R.C.C. balanced 1:1.5:3 R.C.C. balanced 1:1:2 R.C.C. balanced 1:2:4 R.C.C. over reinforced 1:2:4 R.C.C. under reinforced Reinforced brick 1:3:6 R.C.C. balanced

A4.8 Floor

x74 x75 x76 x77 x78

40mm thick 1:2:4 cement, concrete flooring Brick floor in 1:4 cement mortar Brick floor in 1:6 cement mortar Rough chiselled sandstone floor in 1:5 cement mortar Finely chiselled sandstone floor in 1:5 cement mortar

A4.9. Internal plastering

x79 12mm thick plaster in 1:6 cement mortar


×80 x81 ×82 ×83

12mm thick plaster in 1:1:7 cement, lime mortar 12ram thick plaster in 1:2:9 cement, lime mortar 12ram thick plaster in 1:2 lime, surkhi mortar 12mm thick plaster in 1:1:1 lime, surkhi, sand mortar

A4.10. External plastering

×84 x85 x86

12ram thick plaster in 1:6 cement mortar 12ram thick plaster in 1:1:7 cement, lime mortar 12ram thick plaster in 1:2:9 cement, lime mortar

APPENDIX 5

Wageclasses

Wageclass 1 Rs. 0-20 Wageclass2 Rs. 21-24 Wageclass3 Rs. 25-30 Wageclass4 Rs. 30-35 Wageclass5 Rs. > 50

APPENDIX 6

Shares of Various Construction Materials in Total Expenditure Incurred on Typical Pucca House Construction. Source: Sarvekshana

9%

9% 2% 3%

8%

22% 7~

Legend

Stone

Bricks

Iron & steel

Labour

~Lime

17%

'Q Sand

Cement

~ Othom

~ Tiles

cost of co2 reduction in building construction

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