sustainable waste

Sustainable management of

construction waste

for Hong Kong

Professor C.S. Poon

Dept of Civil and Structural Engineering The Hong Kong Polytechnic University

Construction Waste 15 Million tonnes

in 2009

Batching plants

Excavation

Construction

Refurbishment

Renovation

Demolition

Road Work

C&D Waste

15

C&D Waste Generation

Inert C&D materials (mainly sand, bricks and concrete) both suitable for land reclamation and land formation works, are disposed of at public filling areas.

Non inert portion (bamboo, plastics, glass, wood, paper, vegetation and other organic materials) ends up at municipal solid waste landfills.

6

Salvageable Scraps Reuse/Recycling

C&D Waste

C&D Waste Management in Hong Kong

Non-inert Portion - Landfills

Inert Portion Public fills Mixed waste Sorting facility

3

Construction Waste (source EPD)

(2008)

5%

86%

10%

Sorting Facilities

2,080 tpd

Public Fill

Reception Facilities

18,680 tpd

Landfills

1,020 tpd

Total: 21,780 tpd

Figures may not add up to total due to rounding-off

93% 7%

Non-inert

68% 25%

Soft Hard

20% 5%

Recyclable Non-recyclable

Inert

Construction Waste

(Approx. 15.4 M tonnes in Year 2009) (source CEDD)

8 8

C&D Materials Management Facilities

Locations

30

The Problem

Hong Kong will soon be running out of both landfill space and public filling areas.

According to Government sources :

Landfills will be filled up soon.

Limited reclamation projects. Temporary fill banks will be full soon.

12

Delivery of Reclamation Material to Mainland

13

Designated Reclamation Site in Mainland

20km

14

Construction Waste Disposal

Charging Scheme

Implemented on 1 Dec 2005

Government waste disposal

facilities Type of construction waste accepted

Charge per

tonne

Public fill reception facilities Consisting entirely of

inert construction waste $27

Sorting facilities

Containing more than 50% by

weight of inert construction

waste

$100

Landfills

Containing not more than 50% by

weight of inert construction

waste

$125

Outlying Islands Transfer

Facilities

Containing any percentage of

inert construction waste $125

5

Waste Management Hierarchy

1. Avoid waste generation

2. Minimize waste generation

3. Reuse/Recycle the material

4. Proper disposal of waste

AVOID

MINIMISE

REUSE/RECYCLE

DISPOSAL

CWDCS presentation by CS Poon 15

Nature of C&D waste Mixture of inert & non-inert materials

16

Soft inert

materials

Hard inert

materials

Non-inert

materials

FILLS

FILLS/

RECYCL

E

LANDFIL

LS

CWDCS presentation by CS Poon

24

Form work Finish work Concrete

work

Masonry

work

Material

handling

Scaffolding

work

Hoarding

Ranking of Major Waste Producing Processes

on Building Sites

Source : HK PolyU

25

Damaged during

laying

19%

Cutting Waste

39%

Damaged during

storage

11%

Over Order

15%

Damaged during

transportation

16%

Figure 6 Major Causes of Waste for Brick/Block

(Source: Hong Kong PolyU [ 6 ] )

26

Over order

11%

Others

7%Cutting waste

40%

Damaged during

storage

29%

Change of design

13%

Figure 8 Major Causes of Waste for Tiles

(Source: Hong Kong PolyU [ 6 ] )

Source : HK PolyU

35

Dimensional Coordination and

Standardization

36

Minimizing Temporary Works

In Hong Kong, most of the

waste arising from

temporary works is due to

the use of timber

formworks

37


Alternatives to be considered:

system formworks (metal or aluminum

formworks) that can be reused and/or

recycled

Prefabricated elements (facades, slabs,

staircases, etc)

38


Other reusable alternatives to be considered:

Metal temporary work

Metal platform work

Reusable safety system

Metal scaffolding or mixed

bamboo and metal scaffolding

Metal hoarding

39

Waste reduction 0.21

Labor dependence 0.56

Developers requirement 0.76

Familiarity with the construction tecnology 1.11

Construction cost 1.31

Construction time 1.33

Figure 8: Factors that determined a construction method selection

(Question 25)

0.21

0.56

0.76

1.11

1.31

1.33

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Waste reduction

Labor dependence

Developers requirement

Familiarity with the construction tecnology

Construction cost

Construction time

Fa

cto

rs

Index

Construction Method Selection

43

On-site Low Waste Building Technologies

Formworks:

Large panel formwork.

Steel, aluminum and plastic

forms.

Composite steel decking.

Pecaform.

45

Off-site: Precast and Prefabrication

Construction Waste Disposal

Charging Scheme Implemented in Dec 2005

Government waste disposal facilities

Type of construction waste accepted

Charge per

tonne

Public fill reception facilities

Consisting entirely of inert construction waste

$27

Sorting facilities Containing more than 50% by

weight of inert construction waste

$100

Landfills Containing not more than 50%

by weight of inert construction waste

$125

Outlying Islands Transfer Facilities

Containing any percentage of inert construction waste

$125

Aim of Study

How much construction waste has been reduced?

What changes has taken place among building professionals ?

What are the impact of CWDCS on major work trades on construction sites ?

What are the barriers for changes ?

28 CWDCS presentation by CS Poon

Research Methodology

Questionnaire Totally 319 nos. of questionnaires w; 109 nos. of

questionnaires returned

Structured interviews

One to one structured interviews with difference

construction professionals

Case Studies

Three detailed case studies


After the WCS has been implemented, what is the extent of changes (% increase in waste disposal cost) you allowed in bidding new

projects?


1.1%

7.4% 7.4%

19.8% 21.0%

17.3%

9.9%

6.2% 7.4%

2.5%

0 No change

< 0.05% 0.05% < 0.1%

0.1% < 0.3%

0.3% < 1%

1% < 1.5%

1.5% < 2 %

over 2% no answer

Research Findings

Level of Waste Generation (After CWDCS)


5.0%

11.3%

40.0%

28.8%

3.8%

10.0%

1.1%

-15% < -10% -10% < -5% -5% < 0% No change 0% < 1% over 3% No answer

Research Findings

Barriers of On-site Waste Sorting


All respondents Building Engineer Project Manager Quantity Surveyor

Mean Rank Mean Rank Mean Rank Mean Rank

Narrow site access 5.21 7 4.42 4 5.38 7 5.32 6

Limited waste storage area on site 3.70 1 2.58 1 4.35 5 3.44 1

No sorting area on site 3.86 2 4.17 3 3.85 2 3.76 3

Intensive labor cost in sorting wastes 4.19 4 5.75 6 3.21 1 4.62 5

High supervisory to subcontractor's

behaviors

4.16 3 5.75 6 4.29 4 3.47 2

Low waste sortability 4.86 6 5.17 5 4.24 3 5.38 7

Interference with normal site activities 4.55 5 4.42 4 4.76 6 4.38 4

Impractical in using too many waste chutes 5.46 8 3.75 2 5.91 8 5.62 8

Research Findings

Changes after CWDCS implemented


All respondents

Building Engineer

Project Manager

Quantity Surveyor

Mean Rank Mean Rank Mean Rank Mean Rank

Reduction of site wastage level 3.30 3 2.95 3 3.10 3 3.71 5

More efficiency in waste sorting on site 4.15 6 4.86 6 4.38 6 3.56 4

Improvement in materials estimation before ordering

3.82 4 4.14 5 3.57 4 4.00 6

Improvement in inventory monitoring 3.87 5 3.86 4 4.16 5 3.48 3

Increase environmental awareness 2.84 1 2.55 1 2.82 1 2.98 1

Increase materials recycling awareness 3.02 2 2.64 2 2.96 2 3.27 2


Conclusions less than 5% waste reduction has been achieved since the CWDCS

Charge is not high enough to raise the awareness of waste management at construction sites.

Wet-finishing & dry-finishing trades have

undergone little changes

CWDCS has NOT motivated subcontractor to change their methods of construction

On-site waste sorting is more possible at large construction sites

Need to have other measures, such as inclusion of waste reduction requirements

in contractual clauses and government

regulations, to effect the waste reduction

CWDCS presentation by CS Poon 35

Eco-friendly

Construction

Materials

Professor Chi-Sun Poon www.eco-block.hk

93% 7%

Non-inert

68% 25%

Soft Hard

20% 5%

Recyclable Non-recyclable

Inert

Construction Waste

(Approx. 15.4 M tonnes in Year 2009) (source CEDD)

Incoming C&D Materials

Sorting Plant

Inert C&D Materials

suitable for Recycling

Recycled

Aggregates

Sieving Crusher

Recycling Plant

Source :CEDD

C & D Waste Sorting Facility

>250 mm 150-250 mm 150-50 mm

Extension of SENT Landfill

To handle :

Wastes that cannot be incinerated, e.g. construction waste

Possible C&D waste recycling

facility ???

Properties of Recycled Aggregates

40 mm 20 mm 10 mm 5 mm down

Min. dry particle density (kg/cu.m.) 2350 - 2550 2450 - 2600 2450 - 2600 2450 - 2600 2000

Max. water absorption (%) 3.1 - 4.9 1.0 - 4.9 1.4 - 2.6 N/A 10

Max. content of wood and other material

less dense than water (%)0 0 0 0 0.5

Max. content of other foreign materials (%) 0 0 0 0 1

Max. content of fine (%) 0 - 0.3 0.1 - 0.7 1.0 - 3.0 N/A 4

Max. content of sand (

Source: CEDD

Use of Recycled Aggregates in

Concrete in Hong Kong Wetland Park

15,000 m3 RAC used in

pile caps, ground slabs,

external works, mass

concrete etc

Recycled Aggregates for Concrete : Limitations High water absorption (in particular, the recycled fines)

presence of contaminants and other foreign materials

Compressive strength, tensile strength and bond

strength of concrete would be reduced

Drying shrinkage is higher and the creep of concrete

may increase.

Acceptance for structural concrete application is low

Recycled aggregates

Impurities

Eco-blocks

Alternative casting : Pre-cast bricks and

blocks (dry mixed)

Use with waste glass to enhance aesthetics and water absorption

properties

Use with photo-catalyst for valued added properties

Experiment conducted at PolyU

Steel moulds for

fabrication of blocks Hand compaction of the

wet mixed materials

After hand compaction, the

compression was carried out

using a compression machine

at a rate of 600 kN/min twice Manufacturing process in industry

The mixer

Block manufactured

The ingredients were

mixed in the mixer

Hong Kong : in 2009 About 300 tonnes per day; about 1% recycled 99% landfilled

Waste Glass

Factory made blocks

Air Pollutant Removal Paving Blocks

Eco-blocks - 3rd

Generation

Sunlight

Surface layer

Cement +Recycled Glass +

Recycled Aggregate + Photo-catalyst

Base layer

Cement + Recycled Aggregate +

Recycled Glass

Air Pollutants (NOx) Precipitation

NO3 TiO2

Eco-Blocks

Recycled Aggregate Recycled Aggregate + Recycled Glass

Recycled Glass + Recycled

Aggregate + Photo-catalyst

Examples of field applications

5

What can we do with the problems?

Recommendations

1. Avoid waste generation

2. Minimize waste Generation

Better design and construction methods

Change of work practices etc

3. Reuse/Recycle the material

AVOID

MINIMISE

REUSE/RECYCLE

DISPOSAL

Extension of SENT Landfill

To handle :

Wastes that cannot be

incinerated, e.g. construction

waste

Possible C&D waste recycling

facility ???

BEAM Plus

Materials Aspects

Prof. C.S. Poon

(BEAM Faculty / MA panel Chair)

Materials Aspects NB EB

No. of Prerequisites 4 2

No. of Credits 22 11

No. of Bonus 1 2

Credit Summary for NB:

Ma P1 Timber Used for Temporary Works

Ma P2 Use of Non-CFC Based Refrigerants

Ma P3 Construction / Demolition Waste

Management Plan

Ma P4 Waste Recycle Facilities

Ma 1 Building Reuse

Ma 2 Modular and Standardized Design

Ma 3 Prefabrication

Ma 4 Adaptability and Deconstruction

Ma 5 Rapidly Renewable Materials

Ma 6 Sustainable Forest Products

Ma 7 Recycled Materials

Ma 8 Ozone Depleting Substances

Ma 9 Regionally Manufactured Materials

Ma 10 Demolition Waste Reduction

Ma 11 Construction Waste Reduction

Credit Summary for EB:

Ma P1 Use of Non-CFC Based Refrigerants

Ma P2 Waste Recycling Facilities

Ma 1 Building Reuse

Ma 2 Modular and Standardized Design

Ma 3 Adaptability and Deconstruction

Ma 4 Rapidly Renewable Materials

Ma 5 Sustainable Forest Products

Ma 6 Ozone Depleting Substances

Ma 7 Waste Management

BEAM Plus

Materials Aspects

Requirement:

It is required to implement with proof of documentation a waste management system providing

for the sorting, recycling and proper disposal of inert and non-inert construction / demolition

materials.

Ma P3 Construction and Demolition Waste Management Plan Prerequisite

Objective:

Encourage best practices in the management of construction and demolition wastes, including

sorting, recycling and disposal of construction waste.

BEAM Plus

NB Ma P3

Requirement:

1 credit for demonstrating that at least 30% of demolition waste is recycled.

2 credits for demonstrating that at least 60%.

NB Ma 10 Demolition Waste Reduction 2 credits

Exclusion:

Project where demolition is not required or is not under the Clients control.

Remark:

Disposal of inert waste to public fill will NOT be considered.

Objective:

Encourage best practices in the management of waste, including sorting, recycling and disposal of

demolition waste.

BEAM Plus

NB Ma 10

Requirement:

1 credit for use of recycled materials contributing to at least 10% of all materials used in site

exterior surfacing work, structures and features.

1 credit where at least 10% of all building materials used for faade and structural components are

recycled materials.

1 credit where at least 10% of all building materials used for interior non-structural components are

recycled materials.

NB Ma 7 Recycled Materials 3 credits

Objective:

Promote use of recycled materials in order to reduce the consumption of virgin resources.

Remark:

The unit shall be mass/volume/dollar value.

Exclusions:

None.

BEAM Plus

NB Ma 7

Prof. C.S. Poon

Dept of Civil and Structural Engineering

The Hong Kong Polytechnic University

Tel : (852) 2766-6024

Email : [email protected]

Thank You

sustainable waste

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