life cycle assessment as a tool for material selection - …. neha bhatia is an asst.professor in...

Ar. Neha Bhatia is an Asst.professor in the Department of Architecture, Accredited to Pune University, Pune, Maharastra.

Life Cycle Assessment as a tool for

Material Selection - A comparison of

Autoclaved Aerated Concrete and VSBK

Brick Wall Assembly.

Neha Bhatia, M-Arch (Sustainable Architecture)

Pad. Dr. D. Y. Patil College of Architecture, Akurdi, Pune.

[email protected]

1.0 ABSTRACT

Energy use of a building can be derived from five sources: Embodied Energy from mining and

manufacturing of materials, Energy from transportation of materials, Energy from construction of the

building, Energy use during operation of the building, and Energy used in the disposal of the building at

the end of its life. Buildings use many materials with a high Embodied Energy, and it is estimated that,

10% of its total energy use comes from Embodied Energy in materials. Thus, the use of low Embodied

Energy Materials for the sustainable development is preferred. Life cycle assessment (LCA) offers a

comprehensive approach to evaluating and improving the environmental impacts of buildings

materials, buildings and its products through all of its life stages.

Brick and Cement are majorly used materials in building industry. Kiln Burnt Brick is majorly use

exterior wall material in the market. Also, Aerated Concrete (AAC) is a non-combustible, cementitious

building material that is expanding into new worldwide markets.

The Paper will be aimed to compare the environmental impact of materials- Kiln Burnt Brick and

Autoclaved Aerated Concrete used for wall assemblies. Study will be focused on evaluating the materials

with respect to its Embodied Energy, Energy and Resource consumption, Environmental Impact in terms

of CO2 Emissions, Cost, Health safety etc. The functional unit and unit distance will be defined to allow

comparisons to be made between materials. The study will include interaction with the Manufacturers,

Market study of the materials, and use of material in a particular building. The final objective of the

paper is to evaluate the materials on the bases of Life Cycle Assessment Impact Categories which

includes: Raw Material Index (RMI), Water consumption, Embodied Energy (EE) and Operational

Energy (U-Value), Electricity, Occupational Health and Safety (OHS Index), Total Cost, CO2

Emissions.

Key words: - Life Cycle Assessment, Materials, Kiln Burnt Brick, Autoclaved Aerated Concrete, Life

Cycle Assessment Impact Categories.

2.0 INTRODUCTION

Building construction in India is estimated to grow at a rate of 6.6% per year between 2005 and

2030 (McKinsey and Company, 2009). The building stock is expected to multiply five times during this

period, resulting in a continuous increase in demand for building materials, which could have long

lasting implications in terms of natural resource depletion, future energy demand, local pollution,

contributions to greenhouse gas emissions as well as socio-economic conditions of a significant number

of low-income workers. Thus it is an imperative and urgent need to have a comprehensive plan for

development of walling materials production in India, with the least impact to the earth.

30th INTERNATIONAL PLEA CONFERENCE 16-18 December 2014, CEPT University, Ahmedabad

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All materials have environmental implications. Thus the choice of materials for a project requires

considerations of aesthetic appeal, initial and ongoing costs, life cycle assessment considerations (such

as material performance, availability and impact on the environment) and the ability to reuse, recycle or

dispose of the material at the end of its life. It is estimated that, 10% of buildings total energy use comes

from embodied energy in materials. Thus, the use of low embodied energy materials for the sustainable

development is preferred. Life Cycle Assessment (LCA) offers a comprehensive approach to evaluating

and improving the environmental impacts of buildings materials, buildings and its products through all

of its life stages from cradle-to-grave (i.e., from raw material extraction through materials processing,

manufacture, distribution, use, repair and maintenance, and disposal or recycling).

Brick and Cement are majorly used materials in building industry. Kiln Burnt Brick is majorly use

exterior wall material in the market. Also, Aerated Concrete (AAC) is a non-combustible, cementitious

building material that is expanding into new worldwide markets.

3.0 AIM AND OBJECTIVE

The Paper is aimed to compare the environmental impact of materials- Kiln Burnt Brick and

Autoclaved Aerated Concrete used for wall assemblies.

The final objective of the paper is to evaluate the materials on the bases of Life Cycle Assessment

Impact Categories which includes: Raw Material Index (RMI), Water consumption, Embodied Energy

(EE) and Operational Energy (U-Value), Electricity, Occupational Health and Safety (OHS Index), Total

Cost, CO2 Emissions.

4.0 METHODOLOGY

In this assessment the tools of Life Cycle Assessment are integrated, which includes due

consideration of all life cycle stages fixed in the ISO 14040 –14043 standards: Goal and Scope

Definition, Life Cycle Inventory Analysis, Life Cycle Impact Assessment and Life Cycle Interpretation.

Life Cycle Inventory Analysis includes assembling data and analyzing it on a suitable system

boundary. Life Cycle Impact Assessment is the evaluation of the material and energy flows raised in the

inventory analysis according to certain environmental effects.

Figure 1 Methodology use for Life Cycle Assessment.

Thenafter, Impact Assessment categories are selected, which includes: Raw Material Index (RMI),

Water Consumption, Embodied Energy (EE) and Operational Energy (U-Value), Electricity and other

Resources, Occupational Health and Safety (OHS Index), Total Cost, CO2 Emissions. Life Cycle

Interpretation consists of Identification of significant issues, evaluation and conclusions.


2

5.0 SCOPE AND LIMITATION

Study is focused on evaluating only two walling materials - Kiln Burnt Brick and Autoclaved

Aerated Concrete with respect to its formulated Impact Assessment Categories. The functional unit and

unit distance is defined to allow comparisons to be made between materials. The study includes

interaction with the Manufacturers, Market study of the materials, and use of material in a particular

building.

Building use: Evaluation of the materials and energy consumptions is restricted to the use of a

building only, its maintenance and restoring, not considered within this study. Also, Transport of the

wastes generated during the Construction and Demolition phase, not considered within this study. No

consideration of labour cost as it will have negligible effect on the results.

To understand the implication of these materials, the live site data collection is limited to pune

(moderate climate), but to understand the impact of operational energy a theoretically comparative study

base has been done with a case study of composite climate.

6.0 LIFE CYCLE ASSESSMENT

A Life Cycle Assessment (LCA) provides a mechanism for systematically evaluating the inputs,

outputs and the potential environmental impacts linked to a product or process throughout its life cycle.

(ISO 14040). LCA addresses the impacts of a product through all of its life stages.

Life Cycle Assessment is a technique to assess environmental impacts associated with all the stages

of a product’s life from cradle to grave.

6.1 EMBODIED ENERGY

Embodied energy is the total energy required for the extraction, processing, manufacture and

delivery of building materials to the building site. Energy consumption produces CO2, which contributes

to greenhouse gas emissions, so embodied energy is considered an indicator of the overall environmental

impact of building materials and systems. It does not include the operation or disposal of materials.

The total amount of embodied energy may account for 20% of the building’s energy use, so

reducing embodied energy can significantly reduce the overall environmental impact of the building.

Energy consumption during manufacturing can give an approximate indication of the

environmental impact of the material, and for most building materials, the major environmental impacts

occur during the initial processes.

Figure 2 Typical phases of materials Life Cycle, along with inputs and outputs at each phase.

7.0 LIFE CYCLE INVENTORYANALYSIS OF AAC BLOCKS AND VSBK BRICK

7.1 Autoclaved Aerated concrete and Vertical Shaft Brick Kiln (VSBK)

AAC is lightweight, precast building material that simultaneously provides structure, insulations,

and fire & mold resistance. Main ingredients include fly ash, water, quicklime, cement, aluminium

powder & gypsum. The block hardness is being achieved by cement strength, & instant curing

mechanism by autoclaving. Gypsum acts as a long term strength gainer. The chemical reaction due to the

aluminium paste provides AAC its distinct porous structure, lightness & insulation properties,

completely different compare to other lightweight materials.

The VSBK is a vertical kiln with a stationary fire and a moving brick arrangement. The figure

below shows the VSBK principle in a schematic diagram. The kiln operates like a counter current heat


3

exchanger, with the heat transfer taking place between the air moving upwards and the bricks moving

downwards.

(a)

(b)

Particulars Quantity UnitEmbodied

EnergyUnit Total Energy Unit

lime 90.00 kg/cu.mt 5.63 Mj/kg 506.7 Mj

fly ash 450.00 kg/cu.mt 0 Mj/kg 0 Mj

Cement 70 kg/cu.mt 4.2 Mj/kg 294 Mj

aluminium powder 0.5 kg/cu.mt 260 Mj/kg 130 Mj

gypsum 5 kg/cu.mt 1 Mj/kg 5 Mj

Total RM EE 935.7 Mj

Transport 150 Km. 11.93 Mj/Km. 1789.5 Mj

Total 2725.2 Mj

electricity (kWh) 9 kWh/Cu.m. 9.28 Mj/kWh 83.52 Mj

Coal (kg) 0.03 ton/cu.mt 12.3 Mj/ton 0.369 Mj

Total 2809.09 Mj

Water consumption 400 l/cu.mt

human resource 60 no.s 10.04 Mj/day 602.4 Mj275.29 CO₂/cu.m

Quantities of AAC Wall yearly 100000 cum

0.098Kg of CO2 per MJ of embodied energy

Figure 4 (a) Process Flow Chart and (b) Table 1 Embodied Energy calculations for AAC Block

Production.

Note: Data Collection for production process of AAC Blocks is taken from company Anjali Ventures Ltd., Surat.

(a)


EnergyUnit Total Energy Unit

Fired Brick 555.00 unit/cu.mt 7.9 Mj/unit 4384.5 Mj

Total RM EE 4384.5 Mj

Transport 50 Km. 11.93 Mj/Km. 596.5 Mj

Total 4981 Mj

electricity (kWh) 1 kWh/Cu.m. 9.28 Mj/kWh 9.28 Mj

Coal (kg) 6 ton/cu.mt 18 Mj/ton 108 Mj

Total 5098.28 Mj

Water consumption 420 l/cu.mt

human resource 9 no.s 10.04 Mj/day 90.36 Mj

499.63 CO₂/cu.

Quantities of Brunt Bricks (brick weight is app 3kg)

0.098Kg of CO2 per MJ of embodied energy

Energy content of furnace oil = 42.25 MJ/l; energy content of grid electricity = 9.28 MJ/kWh; and energy content of

cement = 4.20 MJ/kg,All Embodied Energy reference:

http://besharp.archidev.org/IMG/pdf/Embodied_Energy_Computations_in_Buildings.pdf

Figure 5 (a) Process Flow Chart and (b) Table 2 Embodied Energy calculations for VSBK Block

Production.


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EnergyUnit Total Energy Unit Particulars Quantity Unit

Embodied

EnergyUnit

Total

EnergyUnit

Volume of wall 107.54 Cu.m. Volume of wall 107.54 Cu.m.

Volume Green mortar 2.15 Cu.m. 3.2 Mj/cu.m. 6.88 Mj Volume mortar 3584.71 Cu.m. 479.14 MjCement 0 Cu.m. 5999.7 Mj/cu.m. 0 Mj Cement 0.07 Cu.m. 5999.7 Mj/cu.m. 419.98 MjTransport 150 Km. 11.93 Mj/Km. 1789.5 Mj Transport 50 Km. 11.93 Mj/Km. 596.5 Mj

Total 1796.38 Mj Sand 2.00 Cu.m. 29.58 Mj/cu.m. 59.16 Mj

Sand 0 Cu.m. 29.58 Mj/cu.m. 0 Mj Electricity 4 kWh 9.28 Mj/kWh 37.12 MjElectricity 2 kWh 9.28 Mj/kWh 18.56 Mj Total 1112.76 Mj

size(625 x 250x 150

mm)0.023438 Cu.m. 42.67 size(230 x 110 x 70 mm) 0.001771 Cu.m.

No.s of blocks 4229.96 no.s/cu.mt 65.84 Mj/Block 2809.09 Mj No.s of blocks 44530.58 no.s 9.03 Mj/Block 5098.28 Mj

Total 4624.03 Mj Total 6211.04 Mj

E.E. of total wall 497274.64 Mj E.E. of total wall 667944.10 Mj

48732.91 kg of CO₂ 65458.52 kg of CO₂

Quantities of brick Wall

0.098Kg of CO2 per MJ of embodied energy 0.098Kg of CO2 per MJ of embodied energy

Quantities of AAC Wall

blocks/ cu,mt 555 brick in 1 cu.mt

(a) (b)

Source: - embodied energy of various materials and technologies - data and summary - 1.pdf

About 0.098 tonnes of CO2 are produced per gigajoule of embodied energy = 0.098Kg of CO2 per MJ of embodied energy

Table 3 Embodied Energy calculations involved in constructing the Wall Assembly of AAC amd

VSBK.

8.0 CASE STUDIES (CLIMATE: COMPOSITE CLIMATE)

8.1 Fortis Hospital – 3 Star rated. (Location: Shalimar Bagh, New Delhi)

The 500 bedded Fortis hospital at Shalimar Bagh is designed with a vision to provide an

environment friendly health care facility in an area of 64,400 sq mts. It is the first hospital building in

India to have registered for the GRIHA green building rating system.

(a) (b)

Figure 6 Energy Efficiency Interventions - Building Envelope (a) Cross Section of Wall and Roof

Assemblies. (b) U value Calculations and Energy Performance Index (EPI).

9.0 LIVE CASE STUDY (CLIMATE: MODERATE)

9.1 Park Turquoise (Location: Wakad, Pune)

Turquoise is Apartment Flats of 2 bhk (1150 sq. ft), 2.5 bhk (1330 sq. ft), 3 bhk (1550 sq .ft).

A Park Turquoise is the luxurious 70-acre township boasting of ample landscaped and open areas.

(a) (b)

Figure 7 (a) Layout of Live Case Study (b) Typical Floor Plan of the Building.

9.2 Construction Techniques

The building envelope has used Autoclaved Aerated concrete blocks instead of conventional bricks.

The windows are glazed units with low thermal transmittance. Building Envelop is of AAC blocks with

external 1:4 cement and sand plaster and internal gypsum plaster.

U-value calculations for 150mm and 200 mm AAC wall=0.76 w/km² degC and 0.61 w/km² degC.

U-value calculations for 150mm and 230 mm VSBK wall = 1.95 w/km² degC and 1.77 w/km² degC


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Figure 8 AAC block Wall Section Brick Wall Section

9.3 Cost Analysis of the Project

All required quantities are refered based on the data collected from the Live Case Study to allow

comparision between the two materials.

Table 4 Comparative cost analysis of Wall Assemblies.

10.0 LIFE CYCLE IMPACT ASSESSMENT OF AAC BLOCKS AND VSBK BRICKS

Based on the data collected from the live case study, Comparative Analysis is been done between

both the materials on various parameters and the results derived from these calculations are as follows:

10.1 Raw Material consumption (per cubic meter of 150 mm thick Non-Loadbearing Wall)

Raw Material Index = (Clay quantity x 2 + Silt x 1 + Sand quantity x 1 + Lime quantity x 1 + Cement quantity x 1 x 1.45

+ Fly ash quantity x 0)/5 Source: www.enzenglobal.com/pdf_downloads/strategy_walling.pdf

Figure 9 Raw Materials in block production and construction of Wall Assemblies.

10.2 Water Consumption (l/m3 for 150mm Non Loadbearing wall).

Figure 10 Water Consumption in Block Production and Construction of Wall Assemblies.

Gypsum Plaster

AAC Block Wall

Exterior wall Plaster0.46

1.84

0.70

3.00

Int. Gypsum Plaster

Exterior wall Plaster

Int. cement sand Plaster

Red Brick Wall


0.46

1.84

0.70

3.00

Int. cement sand Plaster


Int. Gypsum Plaster

Int. Gypsum Plaster

Clay Silt Sand Flyash Cement LimeAlu.

PowderGypsu

m

Raw materia

l

Raw material index

AAC Blocks 0 0 0 450.00 70 90.00 0.5 5 615.50 197

Burnt Bricks 499.50 582.75 499.50 0 0 0 0 0 1581.7 2081.2

0

500

1000

1500

2000

2500

Mat

eri

al u

sed

Raw material

Block production

Unplastered Plastered

T.W Plastered

Wall

T.W Unplatered

AAC Blocks 39655.88 0 200 39855.88 39655.88

Burnt Bricks 44530.58 6219.11 200.00 44730.58 50749.69

0.00

10000.00

20000.00

30000.00

40000.00

50000.00

60000.00

Wat

er

Water consumptionNon-Load bearing walls 150mm thick.

Block

production

Unplastered Plastered T.W Plastered

Wall

T.W

Unplatered

AAC

Blocks

39655.88 0 200 39855.88 39655.88

Burnt

Bricks

44530.58 6219.11 200.00 44730.58 50749.69

Construction Total water consumption


6

http://www.enzenglobal.com/pdf_downloads/strategy_walling.pdf

10.3 Energy Consumption (Embodied Energy and Operational Energy of 150 mm Non Loadbearing

wall).

About 0.098 tonnes of CO2 are produced per gigajoule of embodied energy = 0.098Kg of CO2 per MJ of embodied energy.

Figure 11 Embodied energy (MJ/m3) and Operational Energy (W/m2.deg C) in Wall Assemblies.

10.4 Productivity and OHS (for 150mm Non Loadbearing wall)

Scores for each sub-parameter: High (H) = 3’, ‘Moderate (M) = 2’ and ‘Low (L) = 1; Available (A) = 1’, ‘Inadequate (I)

= 2’ and ‘Not available (NA) = 3, NA=0 for (d), OHS Index = (Sum of scores for each sub-parameter)/9

Figure 12 Occupational Health and Safety Assessment for masonry Wall Assemblies.

10.5 Wall cost for 150mm (AAC) and 230mm (VSBK) Non Loadbearing masonry Wall Assemblies:

Figure 13 Total Wall Cost for masonary construction of Wall Assemblies.

10.6 Emissions:

Figure 14 Emissions related to Wall Assemblies (kg of CO2).

Block production

Transportation (raw

materials &

finished product)

Plastered Unplastered Plastered UnplasteredT.EE

PlasteredT.EE

UnplasteredU value

AAC Blocks 2809.09 1789.5 26.88 6.88 24.00 12.00 4649.47 4617.47 0.75

Burnt Bricks 5098.28 1112.76 519.14 479.14 60.00 30.00 6790.19 6720.19 1.95

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

7000.00

8000.00

Ene

rgy

Embodied energy and oprational energy

Exposure to dust

Exposure to heat

Exposure to air

pollutants

Manual Handling

Risk

Personal protective equipment

Risk of falling

Sanitation facilities

available at

plant

Safe drinking

water

available at plant

Housing for

temporary

workers (d)

OHS Index

AAC Blocks 1.00 1 1 1.00 1.00 1 1 1 0 0.9

Burnt Bricks 1.00 1.00 2.00 2.00 3.00 1.00 3.00 2.00 2.00 1.9

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

Val

ue

s

Occupational Health and Safety

No. of Blocks/ Bricks

required

Value of one Block or Brick

Total value of Blocks

used

Build Fast Plus

mortar

Cement and sand mortar

Masons and

Helpers

water for curing

Reinforced coping

Wastage and

breakage

Steel used in stucture

Manpower for 7 day

curingElectricity

Labour for shifting

and

housekeeping

Total Cost

AAC Blocks 4229.96 86.5 365891.5 45600.00 0.00 33000 0 0 12344.75 1690000. 0 600 2000 2149436.

Burnt Bricks 44530.58 7.50 333979.3 0.00 100371.9 75000.00 20000.00 35847.12 73781.76 1950000. 4000 1680 2500 2597160.

0.00

500000.00

1000000.00

1500000.00

2000000.00

2500000.00

3000000.00

Ru

pe

es

Wall Cost

Non-Load bearing walls 150mm thick.

Production Construction Total CO2

kg of CO2 kg of CO2 kg of CO2

AAC

Blocks

275.29 48732.91 49008.21

Burnt

Bricks

499.63 65458.52 65958.15

Production

AAC Blocks 275.29

Burnt Bricks 499.63

0.00

100.00

200.00

300.00

400.00

500.00

600.00

un

its

CO2 Emissions

Construction

AAC Blocks 48732.91

Burnt Bricks 65458.52

0.00

10000.00

20000.00

30000.00

40000.00

50000.00

60000.00

70000.00

un

its

CO2 Emissions

Total CO2

AAC Blocks 49008.21

Burnt Bricks 65958.15

0.00

10000.00

20000.00

30000.00

40000.00

50000.00

60000.00

70000.00

un

its

CO2 Emissions


7

10.7 Resources used:

http://www.victoria.ac.nz/cbpr/documents/pdfs/ee-co2_report_2003.pdf

The total emission factor for electricity is 16.43g CO2 / MJ.

About 0.098 tonnes of CO2 are produced per gigajoule of embodied

energy = 0.098Kg of CO2 per MJ of embodied energy.

Figure 15 Resources used in wall assemblies /cu mt.

11.0 LIFE CYCLE INTERPRETATIONS

11.1 Overall Comparision

1. It is apparent that masonry units with the least or no clay content (i.e AAC blocks which contains

waste material such as Fly Ash) have low impact. Density also influences raw material impact, thus

AAC blocks resulting from the aerated nature (approximately 80% air) have lower raw material impact.

Larger block size reduces the quantity of mortar wastage on construction site. Additionally, the raw

materials that are consumed are generally abundant and found in most geographic regions, allowing

them to be locally sourced. Furthermore, much of the raw materials used in AAC production may consist

of recycled materials, including copper mine tailings and flyash, a byproduct of coal-fired power plants.

2. AAC blocks use cement in the production process and require curing. However, steam curing

under high pressure (autoclaving) results in significantly lower water consumption. Larger block size

reduces the quantity of mortar used in construction and thus the water requirement on site. Whereas,

Water requires for curing Brick Masonry for 7 days is much large, thus the water consumption increases.

3. Burnt bricks show much higher embodied energy compared to AAC Blocks. The thermal

performance of AAC wall assembly is also generally superior to Burnt bricks as reflected in the U-

values. AAC blocks wall assembly have the lower U-value due to the porous nature of the material.

4. Burnt brick production is traditionally a labour intensive process. The use of manual labour for

moulding therefore results in significantly lower productivity compared to mechanized processes.

Block size also influences construction productivity and a larger block size requires less time and

effort for construction. Poor conditions for labour at brick kiln sites are reflected in OHS index

compared to AAC. Units producing AAC Blocks are generally located close to large urban areas and do

not require labour to live on site during the production period as in the case of Burnt Brick.

5. Cost of AAC block is higher but the overall cost of the construction reduces drastically. Due to

the larger block size of AAC masonry reduces the mortar quantity contributing to lower cost for the wall

assembly. Also due to its lightweight characteristics the steel consumption reduces by 0.4kg which lower

the total cost of construction.

6. CO2 emissions are lower for AAC Production and Wall Assembly compared to Burnt brick

Walls and its production.Also, Resource Consunmtion of AAC is lower and thus the CO2 emmissions.

ACKNOWLEDGEMENT

I would like to thank people of AAC block production company Anjali Ventures Ltd., Surat.

12.0 REFERENCES

1. 2003, from http://www.victoria.ac.nz/cbpr/documents/pdfs/ee-co2_report_2003.pdf.

2. Krishnakedar. S. Gumaste, 2006, from

http://besharp.archidev.org/IMG/pdf/Embodied_Energy_Computations_in_Buildings.pdf.

3. 2011, from http://www.enzenglobal.com/pdf_downloads/strategy_walling.pdf

4. from, http://www.vsbkindia.com/factfile.htm

electricity (kWh)

Coal (ton) ElectricityTotal

ElectricityTotal Coal

AAC Blocks 9.00 0.03 2 11.00 0.03

Burnt Bricks 1.00 6.66 4.00 5.00 6.66

0.00

2.00

4.00

6.00

8.00

10.00

12.00

Un

its

ResourcesNon-Load bearing walls 150mm thick.

Construction

electricity

(kWh)

Coal (ton) Electricity Total

Electricity

Total Coal kg of CO2 kg of CO2 Total CO2

AAC

Blocks

9.00 0.03 2 11.00 0.030.18073 0.00285 0.18358

Burnt

Bricks

1.00 6.66 4.00 5.00 6.660.08215 0.6327 0.71485

EmissionsTotal water consumptionProduction


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http://www.enzenglobal.com/pdf_downloads/strategy_walling.pdf

http://www.vsbkindia.com/factfile.htm

life cycle assessment as a tool for material selection - …. neha bhatia is an asst.professor in...

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