recycling of demolition waste and strategies

Table of contents

iTable of contents

viList of tables

viiList of Figures

viiiAbbreviations

ixAcknowledgement

xiDeclaration

xiiAbstract

CHAPTER 01 Introduction11.0 Introduction

11.1 Background

31.2 Aim and objectives

41.3 Research Methodology

41.3.1. Literature survey and review

41.3.2. Semi structured Interviews and Observations

41.4 Scope and limitations

51.5 A Guide to Dissertation

CHAPTER 02 Literature Review on Demolition waste Recycling

62.1 Demolition Waste

62.1.1 What is demolition waste?

72.1.2 Classification and Composition of Demolition Waste

82.1.3 Building Demolition techniques

92.2 Recycling of demolition waste

92.2.1 What is Recycling?

112.2.2 Benefits of Recycling of Demolition waste

122.2.3 Recycling methods

122.2.3.1 Source separation

122.2.3.2 Commingled recycling

122.2.3.3 Comparison of Source separation and Commingled recycling process

142.2.4 Demolition Waste processing

152.2.4.1 Comparison of Mechanically intensive vs labour intensive processing

152.2.4.2 Comparison of on site and off site crushing and sorting

162.2.5 Separation Process in Recycling

172.2.4.1 Water based separation

172.2.4.2 Air flow based separation

192.2.6 Crushing process in Recycling

202.2.7 Demolition waste material, Origin, Ways of collection, Ways of sorting, Recycling process, Technologies and End market/products

202.2.7.1 Concrete

222.2.7.2 Brick

232.2.7.3 Wood, Timber

252.2.7.4 Metal (Ferrous)

272.2.7.5 Metal (Non ferrous)

292.2.7.6 Tiles

302.2.7.7 PVC/Plastics

322.2.7.8 Asbestos

332.2.8 Commonly used Recycling Plant Technology

342.2.8.1 Demolition waste processing equipment

382.2.8.2 Demolition waste Processing flow diagram

392.3 Economics of the recycling of Demolition waste

422.3.1 Market analysis of Recycled products

422.3.1.1 Specification (Quality)

432.3.1.2 Quantity

432.3.1.3 Price of the recycled product

442.4 Market Development

442.4.1. Set goals for Market development

452.4.2. Identification the Barriers and opportunities

462.5 Government Intervention

462.5.1 Regulatory Background in Other countries to Support C&D Recycling

482.5.2 Regulatory Background in Sri Lanka

492.6 Summary

CHAPTER 03 Research Methodology

503.0 Introduction to research methodology

503.1 Research process

503.1.1 Literature review

513.1.2 Research problem statement

513.2 Research Design

513.2.1 Research approach

513.2.1.1 Case study design

523.2.2 Research techniques

523.2.2.1 Data collection techniques

543.2.2.2 Data analysis techniques

563.3 Applications of Case study

563.3.1 Analysis of existing Demolition waste Recycling practice

563.3.1.1 Method of data collection

563.3.1.2 Method of data analysis

563.3.2 Analysis materials which can recycling with existing techniques but not yet recycling

573.3.2.1 Method of Data Collection

573.3.2.2 Method of data analysis

573.3.3 Analysis materials which cannot recycle with existing techniques and materials which are can improve recycling perspective of other countries recycling techniques

573.3.3.1 Method of data collection

573.3.3.2 Method of Data Analysis

583.3.4 Analysis of economic feasibility of recycling each waste materials

583.3.4.1 Method of data Collection

583.3.4.2 Method of data Analysis

583.4 Significance of the study

593.5 Justification for selecting case study method

593.5 Research Reliability and validation

603.6 Summary

CHAPTER 04 Research Findings Analysis and discussion

614.1 Objective 01 - Analysis of existing Demolition waste Recycling practice

614.1.1 Introduction

624.1.2 Analysis of demolition waste materials which are currently recycling

624.1.2.1 Timber

624.1.2.1.1 Extents of recycling

624.1.2.1.2 Ways of collections

624.1.2.1.3 Ways of sorting

634.1.2.1.4 Recycling methods

634.1.2.1.5 Process of recycling

634.1.2.1.6 Recycling processing strategies used

644.1.2.1.7 Recycling technologies used

644.1.2.1.8 End materials/markets

644.1.2.2 Concrete

644.1.2.2.1 Ways of collection


654.1.2.2.3 Process of Recycling

654.1.2.2.4 Process of screening/sieving

654.1.2.2.5 Technologies used

654.1.2.2.6 End markets/products

664.1.3 Analysis of Demolition waste materials which are currently not recycling

664.1.3.1 Reasons for not recycling each of these demolition waste materials

674.1.3.2 Government intervention regarding demolition waste land filling

674.1.3.3 Opportunities for treat or recycle

684.1.4 Summary

694.2 Objective 02 - Analysis materials which can recycle with existing techniques but not yet recycling


694.2.2 Materials which can be recycle with existing techniques but not yet recycle

704.2.3 Particular recycling techniques which can recycle these materials

704.2.3.1 Ways of collections

704.2.3.2 Ways of sorting

714.2.3.3 Recycling methods

714.2.3.4 Processes can use for recycling

714.2.3.5 Processing strategies can use to recycling

734.2.3.6 Recycling technologies can use to recycle

734.2.3.7 End markets/products

734.2.4 For what extent these materials can be recycling

734.2.5 Barriers to recycle these materials

744.2.6 How can recycle materials using other countries recycling techniques?

744.2.6.1 Brick







754.2.6.2 Tiles



764.2.6.2.3 Recycling process

764.2.6.2.4 Technologies

764.2.6.2.5 Recycled material Applications

764.2.6.2.6 Market/End products

764.2.6.3 Concrete







784.2.7 Summary

794.3 Objective 03 - Analysis materials, which are cannot recycle with existing techniques and can improve recycling perspective of other countries recycling techniques.


794.3.2 Materials which are can not be recycling with existing techniques

794.3.2.1 Asbestos

804.3.3 How can be recycling these materials with perspective of other countries recycling techniques?

804.3.4 Reasons for not recycling these materials

804.3.5 Summary

814.4 Objective 04 - Analysis of economic feasibility of recycling


824.4.2 Analysis economical feasibility if materials are recycling using existing recycling techniques which are can recycle with existing techniques but not yet recycle.

834.4.2.1 Feasibility of Bricks Recycling

844.4.2.2 Feasibility of Concrete Recycling

854.4.2.3 Feasibility of mixed waste (Concrete, bricks, and tiles) recycling

864.4.3 Analysis economical feasibility if materials are recycling with perspective of other countries recycling techniques which are can recycle with existing techniques but not yet recycled.

874.4.3.1 Feasibility of Bricks Recycling

884.4.3.2 Feasibility of Concrete Recycling

894.4.3.3 Feasibility of mixed waste (Concrete, bricks, and tiles) recycling

904.4.4 Analysis economical feasibility if materials are recycling perspective of other countries recycling techniques which are can not be recycle with existing techniques.

904.4.5 Summary

CHAPTER 05 Conclusion, Recommendation and further research915.1 Conclusions

945.2 Recommendation

975.3 Further research

98References

104LIST OF APPENDIcES

List of tables

13Table 2.1: Comparison of Source separation and Commingled recycling process

16Table 2.2: Advantages and disadvantages of on-site & off-site crushing and sorting

37Table 2.3: Demolition waste processing equipments

41Table 2.4: Relationships between Disposal, Processing and Recycling

61Table 4.1: Existing demolition waste recycling practice

63Table 4.2: Timber recycling processing strategies

72Table 4.3: Concrete, Brick and Tiles recycling processing strategies

List of Figures

7Figure 2.1: Composition of demolition waste materials

17Figure 2.2: Water based separating techniques.

18Figure 2.3: Demolition waste separation process

19Figure 2.4: Demolition waste crushing process

21Figure 2.5: Flow chart of basic recycling plant and production of aggregate

34Figure 2.6: Appropriate recycling techniques

36Figure 2.7: Cross section of a Jaw crusher mounted on a mobile Equipment

38Figure 2.8: Demolition waste Processing flow diagram

52Figure 3.1: Research design

ABBREVIATIONS

C & D

- Construction and Demolition

UK

- United KindomPVC

- Poly Vinyl ChlorideEU Countries

- European CountriesAROR

- Average Rate of Return

NEA

- National Environmental ActCEA

- Central Environmental AuthorityHSC

- Health and Safety CommissionACKNOWLEDGEMENTThe research concluded owes much dedication and appreciations to many people who have contributed in numerous ways and it is my pleasant task to acknowledge all the individuals those who supported and extend their king corporation in different manner in order to complete this study successfully.

First and foremost I would like to take this opportunity to convey my heartfelt gratitude towards my supervisor Dr. R. Rameezdeen, former head of Department of Building Economics for giving critical insight and for correcting and editing the dissertation.

I would like to express my gratitude to Dr. Sepani Senarathne for her support as the dissertation coordinator and all the other staff members of Department of Building Economics for their continuous support towards the achievement of this dissertation.

In addition, I would like to convey my heartfelt gratitude to all the demolition contractors who appreciate my endeavor, facilitate for the interviews, collection of information and for extending their helping hands towards me and also for many people, whose names are not mentioned here.

Also I would like to pay my all batch mates for giving their maximum support to achieve my goals.

Finally I owe my exceptional appreciation and gratitude to my parents and family members for the spiritual and emotional reinforcement throughout the study and for the sustained corporation.

Shantha K.S.

Aprial, 2009DEDICATION....

To my beloved parents

For their endless encouragementDECLARATION

I here by declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which, to a substantial extent, has been accepted for the award of any other degree or diploma of a university or other degree or diploma of a university or other institute of higher learning, except where an acknowledgement is made in the text.

.

Shantha K.S.

Date24th of Aprial 2009ABSTRACT

As environmental protection had been pressing hardly in all over the world, the pollution generation from building demolition activities seems difficult to control while waste problem is the major element in the pollution generation. For control the demolition waste generations in Sri Lanka reuse and recycling of demolition waste should be well encouraged. However, the existing waste recycling techniques did not encourage the various recycling materials and encountered difficulties from various directions. There fore it is essential to identify potentials for recycling of demolition waste with perspective of other countries recycling techniques. Hence, this research focuses only on demolition waste recycling practice and identification of potentials for demolition waste recycling materials with perspective of other countries recycling techniques.

Through this research study, analysis of existing Demolition waste recycling practice and for what extent those materials are recycling and what are the techniques used, analysis of materials which can recycle with existing techniques but not yet recycling and how can recycle these by using other countries recycling techniques, analysis materials which cannot recycle with existing techniques but which are can improve recycling perspective of other countries recycling techniques, and finally examine the economical feasibility of above each procedures are the involving main steps. Five demolition contractors were randomly selected who often have good knowledge on demolition waste recycling practice and ten interviews conducted among them to obtain data regarding above matters. Through research studies Concrete, Bricks, Tiles and Timber were identified as most significant waste materials.

When considering other countries recycling materials and their recycling techniques there are many possibilities to recycle demolition wastes in to new products/materials. But still in Sri Lanka recycling of demolition waste is in initial stage and only few studies were carried out and there are lack of knowledge regarding demolition waste recycling techniques. Through this research identified potential recycling materials, recycling techniques and economic feasibility of each recycling operation and the results of this study provide basic platform to recycling of demolition waste materials and to enhance recycling of demolition waste in Sri Lanka.

Key words: - Demolition waste, Recycling, Recycling Techniques, Potential materials, other country's Recycling Techniques, Market Development, Government Intervention.

CHAPTER ONE

INTRODUCTION

1.0 Introduction

1.1 Background

Building demolition represents the process in which an erected structure is purposely destroyed to form a diversity of components and fragments of mixed materials. The demolition process of a building is normally regarded as an unavoidable annoyance in its lifecycle (pun et al., 2005). Demolition of constructed structure has earned negative reputation for the construction industry due to the enormous amount of waste sent to the landfills (pun et al., 2006).

According to Nancy and Patterson (2004) with the waste generation is increases to counteract the amount of waste generation communities have instituted recycling programs. Recycling is the collection and separation of materials from waste and subsequent processing to produce marketable products (Leigh and Patterson, 2004). As a major waste management approach more concentration on recycling is important (Montecinos and Holda, 2006). Recycling has economic and environmental benefits for communities. First, recycling reduces the need for new landfills and their associated costs. Second, recycling can provide materials for construction (Leigh and Patterson, 2004).

Economic benefits in recycling of demolition waste depends on influences of the techniques used for demolition, ways of sorting and separation, Recovery/Recycling rate of each material, techniques used for recycling operation, behavior of demolition workers, etc. Recovery/recycling rate depend on the demolition techniques used (Dissanayake, 2007). Since many demolition materials have high potential for recycling the identification of potential for recycling of demolition materials is very important (Montecinos and Holda, 2006). Demolition waste recycling loop consist of the three main phases of collection, recycling and marketing (Saotome, 2007). Examine the barriers to closing the recycling loop and the identification of possible solutions for promote recycling demolition waste material is essential.

For successful recycling operation the techniques utilized must be clearly establish and the proper equipment and machinery to perform the operation will ultimately be determined by how efficiently the machinery and crews perform the tasks required (Peng et al., 2005). So that market development of recycled end uses also improves the economics of recycling (Sutherland, 2001). When considering a recyclable materials, three major areas needs to be taken in to account such as economy, compatibility with other materials and material properties ( Mindess et al., 2003 cited in Tam and Tam, 2005).

Still in Sri Lanka recycling of demolition waste materials are not very popular in the industry. The key to an effective recycling operation and waste reduction program is proper planning, proper techniques uses and proper development of market for recycled end uses. Identification of target materials that can be recycled is another important matter and to success the recycling operation target materials should be generated in significant quantities. According to type of building generated demolition waste may vary. In Sri Lanka 86.92% of demolition projects are residential building (Dissanayake, 2005). There fore high amount of demolition waste generated from residential building.

According to Domingo (2006) demolition waste consist 60% of brick and cabok and from that around 90% of the waste has opportunity of reusing and recycling and other materials such as glass, steel, plastics, timber, ceramics, etc have insignificant contribution to the total demolition waste quantity and these materials has high potential ability of reuse and recycling.

According to Dissanayake (2005, p26) Demolition waste recycling in Sri Lanka is limited to wood products only. Therefore, identification of potential of recycling for other materials and establishing a successful demolition waste recycling operation in Sri Lanka is very essential. But establishing a successful demolition waste recycling operation in Sri Lanka is a challenge today. Especially because lack of knowledge on recycling techniques, lack of knowledge on recycled end materials/uses markets, less experience in demolition recycling operations, less trained supervisors and employees, financial capacity, knowledge of environmental and safety regulations, etc (Peng et al.,1995).

In order to identify potential of recycling for demolition waste and to accomplish an economically, financially, socially, legally and environmentally feasible waste recycling program it is very much important to be aware techniques used for recycling operation and other factors such as composition of demolition waste materials, ability of recycling demolition waste materials, their recycling rates, recycled end materials/uses, recycled end materials/uses market, economic benefits from recycling operation, assessment of risk etc. To do this it is most important to aware other countries recycling materials, ways of collecting, ways of sorting, recycling techniques, recycled end materials/uses and applications, critical recycling strategies.

1.2 Aim and objectives

AimThe aim of this research can be outlined as identification of potential for Recycling of demolition waste and strategies for successful demolition waste recycling operations in Sri Lanka perspective of other countries recycling techniques through qualitative approach.

Objectives

In order to achieve above aim the following objectives were formulated.

Identify existing Demolition waste Recycling practice and for what extent those materials are recycling and what are the techniques used.

For this, study the materials which are currently recycling and not recycling, ways of sorting, ways of collecting, recycling techniques, recycled end materials/uses, their recycling cost and revenue.

Identify the materials which are can recycling with existing techniques but not yet recycling.

For this, study the materials which are can recycling with existing techniques but not yet recycling, for what extent these materials can recycling, what are those recycling techniques, what are the barriers to recycling and how they can recycling with perspective of other countries recycling techniques.

Identify the materials which are cannot recycling with existing techniques but can improve recycling perspective of other countries recycling techniques.

For this, study the materials which are cannot recycle with existing techniques, reasons for that and how can improve recycling of those materials perspective of other countries recycling techniques including ways of sorting, ways of collection, recycling process, technology, recycled materials applications/end uses etc using following interview guidelines.

Examine the economical feasibility by identifying cost and revenue associated with recycling program to recognize potential recycling materials in Sri Lanka.1.3 Research Methodology

1.3.1. Literature survey and review

Comprehensive literature survey and review was carried out to identify potential of recycling materials and promoting recycling program in Sri Lanka. For this, literature survey and review was carried out identifying other countries recycling materials and their recycling techniques and successful strategies of demolition waste recycling operations. Identification of these methods is main objectives of this research study. This was done referring books, journals, thesis, and electronic materials.

1.3.2. Semi structured Interviews and Observations

Semi structured interviews and observations were conduct among expertise in the demolition waste recycling field to identify existing demolition waste recycling practices including demolition waste materials which are currently recycling and not recycling and to identify how this could be improved perspective of other countries recycling techniques.

1.4 Scope and limitations

The scope and limitations of this research can be summarized as follows;

The Semi Structured Interviews and observations are limited only for demolition contractors who selected for case study for data collecting purposes regarding existing recycling practices of demolition waste materials, identifying potential recycling materials in Sri Lanka, their recycled end uses, market conditions, existing technique, and other countries recycling techniques and how this could be improved.

1.5 A Guide to Dissertation

The dissertation comprises with five chapters including the introduction chapter.

Chapter One: - The background to the study, aim, objectives, scope & limitations of the study and structure of the report were described in this chapter. Chapter Two: - Comprehensive literature review was given on demolition waste recycling practices. This chapter describes techniques used in other countries including origin of waste material, ways of collection, ways of sorting, recycling technology, recycled end material/uses and applications of recycled end materials/uses.

Chapter Three: - This chapter was allocated for discussion of research methodology including the data collection methods and data analysis techniques for the study.

Chapter Four: - Research findings analysis and discussion was presented in this chapter.

Chapter Five: - Conclusion was drawn in this chapter while giving recommendations and highlighting the areas for further research.

CHAPTER TWO

LITERATURE REVIEW ON DEMOLITION WASTE RECYCLING

2.1 Demolition Waste

2.1.1 What is demolition waste?

The construction industry consumes huge amounts of natural resources and produces a significant quantity of construction and demolition wastes (Poon et al., 2004). Waste is produced in different types and quantities throughout the life-cycle of a building with the bulk of the waste being produced during the construction and demolition phases (Dolan, 1999).

Demolition wastes are waste arising from the total or partial demolition of buildings or civil infrastructure. These materials may be soil, gravel, pieces of concrete, ceramics, coats, bricks, overlay plates, tiles, plaster, sand, stones, pieces of sanitary ware, etc. The materials of demolition waste are generally heterogeneous and arise from total or partial (selective) demolition of buildings or other civil engineering infrastructure (Symonds, 1999).

Ekanayake (2000) defined C&D waste as Any material, apart from earth materials, which needs to be transported elsewhere from the construction site or used within the construction site itself for the purpose of filling, incineration, recycling, reusing or composting, other than the intended specific purpose of the project due to material damage, excess, non use, or non compliance with the specifications or being a by product of the construction process.

The waste stream termed C&D waste can cover a wide range of materials and depending on their origin, they can categorize. Their composition varies depending on the type, shape, age, use, size and the main material of the building or civil infrastructure. The challenge is to reduce or eliminate the wastes that follow the various paths leading to the landfill (Dolan, 1999).Demolition wastes usually contain a large amount of reusable materials. If sorted properly these materials could be better to reused or recycled (Poon et al., 2004).

2.1.2 Classification and Composition of Demolition Waste

Characterization of demolition waste is very significant to managing the recycling operation. The potential success of the project will depend on accurately identifying both the nature of the waste and its quantity (Domingo, 2006). According to Domingo (2006) studies demolition waste composition of residential and commercial buildings within Sri Lankan can be shown as follows:

Figure 2.1: Composition of demolition waste materials

These estimated compositions guide to demonstrate the types of materials and percentage that comprise demolition debris. The actual waste compositions from each site can vary considerably based on the type of construction techniques used, the primary structural materials employed (e.g., wood, steel, concrete, brick), and the type of structure being demolished (Lennon, 2005).

Above figure shows that Cabok, Bricks, Mortar, Mixed waste and Concrete shows the highest waste compositions which are amount to 29.85%, 28.67%, 15.24%, 11.80%, 6.77% respectively. So that while Timber and Earth/Clay shows between 1%-2%, steel, glass, wires, etc shows compositions less than 1% out of total waste stream (Domingo, 2006).In addition to that demolition waste stream consist with significant proportion of hazardous wastes such as asbestos, lead pipes and roofing material, other heavy metals, hydrocarbons, paint, adhesives, wood treated with preservatives, contaminated soil and various materials containing PCBs (polychlorobiphenyls) (Strufe, 2004). Demolition waste has a high recycling potential because the majority of it consists of masonry, concrete, and steel (Lauritzen, n.d.). But Domingo (2006) further identified that in Sri Lanka recycling operation is limited only for timber material. There for identification and development of potentials for recycling other materials are very important.

2.1.3 Building Demolition techniques

There are four demolition techniques as Selective demolition, Mechanical demolition, Hybrid and Implosion, where identified by several authors (e.g. Hendriks and Pietersen, 2000; Dissanayaka, 2007; Dolan, 1999).

Selective demolition is carried out manually with the help of small tools. It is a process of selectively and systematically dismantling building to reduce the amount of waste created and generating and supply of high value secondary materials that are suitable for reuse and recycling (Schultmann, 2003). Method shows different types and fractions of materials are removed at the source by step by step and sorted in order to avoided the mixing them. This result in clean fractions of recyclable demolition materials, leading to higher quality recycled materials. Thus in this method a major component enabling high demolition waste recovery rates to be achieved (Dolan, 1999). Main thing is in this method is less plant cost and less waste disposal charges. This method of demolition requires more labour intensive inputs and due to the increased labour input, the associated costs can initially increase with comparing mechanical and traditional demolition methods. Due to the increased labour input for selective demolition the associated costs can increase than other methods. (Peterson et al., 2004).

Mechanical demolition is carried out with the assistance of heavy equipment, generally using backhoe. This method is both efficient and cost effective compared to selective demolition technique. But in this method material reuse and recycling is not likely to occur due to lack of separation and contamination and mixed debris are most suitable to sent for landfills.

Hybrid demolition techniques are combination of mechanical and selective demolition. In this method cost of demolition, economics benefits and environmental impact is compromise between high and low value (Poon et al., 2004). This method is the common method used by most demolition contractors.

For every demolition project it is very important to choose both environmentally and economically friendly demolition techniques. By Dissanayake (2007) analysed both environmentally and economically feasible demolition techniques by using cost, revenue, profit and demolition waste indices. According to findings of several authors revealed that selective demolition is the best technique because it has the greatest profit over the other techniques, which offset incurred comparatively higher costs by comparatively higher revenue earned from selling secondary materials (e.g. Peterson et al., 2004; Schultmann, 2003; Dissanayaka, 2007; Tam and Tam, 2005; Poon et al., 2004). Further it has the higher recovery rates over the other techniques.

Hybrid techniques have second best profit and its greatest cost will offset by its revenue. The mechanical techniques have the lowest cost. But this method has the lowest profit due to its low revenue.

2.2 Recycling of demolition waste

2.2.1 What is Recycling?

Definition

Recycling is the collection and separation of materials from waste and subsequent processing to produce marketable products (Leigh and Patterson, 2004). Recycling prevents useful material resources being wasted, reduces the consumption of raw materials and reduces energy usage, and hence greenhouse gas emissions, compared to virgin production Dolan (1999). Recycling is a key concept of modern waste management and is the third component of the waste hierarchy (Reduce, Reuse, Recycling). Numerous materials can be recycled, with the most common being wood, concrete, Brick, Metals (Montecinos and Holda, 2006). Recycling is widely assumed to be environmentally beneficial, although the collection, sorting and processing of materials into new products also entails significant environmental impacts (Craighill and Powell, 1999).

The benefits of recycling of waste streams from building demolition include diversion of waste materials from landfill sites and reduced depletion of natural resources (Thormark, 2000; Nisbet, n.d.; Gorgolewski, 2006).

Further, Recycling Supplies valuable raw materials to industry, Prevents emissions of many greenhouse gases and water pollutants, Saves energy, Creates jobs, Stimulates the development of greener technologies (Leigh and Patterson, 2004):

The requirements for recycling of Demolition waste are:

As Symonds (1999) following requirements to be fulfill for recycling of Demolition waste.

Land filling of Demolition waste must be prohibited or permitted with very high costs

Landfills must be well managed, and fly tipping of waste must be uncommon and subject to sanctions

The opportunity must exist for the main bulky inert fraction of the Demolition waste to be treated or recycling

Planned demolition, including selective demolition and separation, must take place to allow for effective recycling.

Acceptance by all parties concerned that Demolition waste recycled products should meet no discrimination in the market place.

The opportunity must exist to receive economic benefits from the recycling operation.

Should possess required technological level to produce good quality recycled products

Recycling of demolition waste is still a new concept to the Sri Lankan construction industry (Domingo, 2006). But considering other countries especially European countries such as Germany, Denmark, Netherland Sweden and UK etc can see they reach high level of recycling rate. According to Symonds (1999) European countries such as the Germany, Netherlands and Denmark have achieved higher recycling rates between 80% and 90% and in addition to that Sweden and UK also have relatively high level of recycling rate than other EU countries.

According to COWAM study (2007) Germany and Denmark each recycle more than 85% of all C&D wastes and the UK and Sweden recycle 68% and 28% (estimated) respectively. Therefore, in this research high priority gives to details available in Germany, Netherlands, Denmark, Sweden and UK for recycling techniques analysis.

In these countries waste management hierarchy, recycling ranks higher than incineration with energy recovery and land filling ranks lowest. Recycling is the highest ranking waste treatment form and it ensures better exploitation of resources in waste (Montecinos and Holda, 2006).

2.2.2 Benefits of Recycling of Demolition waste

Recycling of demolition waste materials in to new products will lead to gain environmental, economical and social benefits:

It reduces the demand for raw materials by extending their life and maximizing the value extracted from them.

Reduce the illegal dumping is one of the main benefit from recycling and it will leads to following sub benefits including (Leal et al., n.d.),

elimination of illegal dumping on roads will reduce problems with traffic jams and accidents caused by bulky waste, dangerous blockages of storm water drains

Eliminating of illegal landfills will leads to reduce drinking water contaminations, preventing monsoon runoff and causing floods and promoting mosquito breeding.

It reduces the habitat damage, pollution and waste associated with the extraction of raw materials.

It reduces transport costs and pollution from transporting raw materials and manufacturing new products.

It saves energy in the production process when compared with the energy consumed in using raw materials.

It reduces emissions to air and water in the production process.

It reduces disposal shock (if more waste is recycled, less waste goes to landfill or incinerators).

It promotes personal responsibility for the waste we create.

Helps communities, contractors, and building owners comply with state and local policies, such as disposal bans and recycling goals

2.2.3 Recycling methods

2.2.3.1 Source separation

Source separation means separating different recyclable materials from other waste and intending to recycle (Lennon, 2005). That is, workers keep metals separate from wood and wood separate from concrete, and so on, and place each material into a different container. These containers are then transported to different markets. This enhances recycling possibilities and large proportion of building and demolition waste can take directly to a recycling plant (Lennon, 2005). The economic benefits of recycling are highest if waste materials can be separated from each other and recycled individually.

2.2.3.2 Commingled recycling

Commingled recycling is the mixed waste recycling method and it is an alternative to source separation. Commingled recycling means placing all recyclable materials into a single container which is contains mixed recyclable demolition waste and it is then transported to a processing facility, where different materials are separated by hand or by automated equipment (Lennon, 2005; Anon, 2004).

2.2.3.3 Comparison of Source separation and Commingled recycling process

In these two methods the biggest tradeoff is the complexity versus economics. Source separation is more complex because workers must separate waste materials before they throw them away, there are more containers on site, and there are more markets. In most cases, source separation is economically more advantageous than commingled recycling, because (Lennon, 2005):

Source separation produces materials that are ready to go directly to market; there is no need to pay a processor to sort materials.

Source separated materials are generally of higher quality, with fewer contaminants, so theyre worth more in recycling markets.

Source separation and commingled recycling have following advantages and disadvantages (Lennon, 2005).

Recycling Method Advantages Disadvantages

Source Separation

Higher recycling rates

Lower recycling costs; revenues paid for some materials

Often a cleaner, safer work site Multiple containers on site

Workers must separate materials for recycling

More complex logistics

Multiple markets; more information to manage

Commingled Recycling

Only one or two containers on site

No need for workers to separate materials for recycling

Easier logistics

One market; less information to manage Lower recycling rates

Higher recycling costs

Table 2.1: Comparison of Source separation and Commingled recycling process

Complexity is usually not much of an issue. Its no harder for workers to throw different materials into different containers than to throw them out mixed together. Being smaller, containers for source separated materials can often be placed close to work areas, so that source separation actually takes less time and effort than carrying wastes to a central container for mixed debris. On balance, source separation is generally preferable to commingled recycling. It costs less, and recycling rates are typically higher. There are some jobs where commingled recycling is the only option possible, because of site limitations, job size, or schedule. In these cases the goal is to identify the commingled processor who can achieve the best combination of price and recycling rate. But where its feasible, source separation should be considered the best recycling option.

2.2.4 Demolition Waste processing

Demolition waste processing consists with crucial factors such as Sorting, Separation, Crushing, Sifting and secondary crushing. The initial operation may be a simple manual sorting (e.g., salvage) of the demolition waste and it is a more complicated process with considering time factor because most of contractors main aim is rapid demolition and disposal of structures (Symonds, 1999). The organization of the processes into elements that perform discrete tasks (e.g., separation, size reduction) is based on an understanding of the characteristics of the demolition waste stream to be handled. Because many systems contain mobile equipment, the initial choice of infeed, discharge and recycling systems may be revised as characteristics of feed and products change (Stein and Savage,1994). Demolition contractors are quite familiar with the practice of recycling materials that can be separated and recovered from building debris. However demolition Waste processing strategies may consist with either;

Sort and separate, Crush and reduce or;

Crush and reduce, Sort and separate.

Processing systems may incorporate trommel, disc or vibratory flat-bed screens to separate rocks and soil from the remaining waste. Density separation (e.g., pneumatic or hydraulic sink/float operations) diverts wood scrap from heavier fractions. After processing, a substantial non recyclable fraction of the waste stream usually remains as a process residue requiring disposal.

Various approaches have applied for processing C&D debris into useful products.

These approaches are generally classified as (Stein and Savage,1994):

Mechanically intensive or labour intensive

On-site or off-site processing (e.g. at a central facility).

The selection of the location where the management of C&D waste (crushing and separation) could take place (on-site or off-site) is based on the following parameters (Kourmpanis et al., 2008). Availability of machines.

Required quality of recyclable materials in order to be used at the worksite.

On-site space availability.

Distance between the worksite and the nearest Recycling Centre.

2.2.4.1 Comparison of Mechanically intensive versus labour intensive processing

A labour intensive process means that operators are selecting and sorting material, with the aid of mechanical equipment. The difference between mechanically intensive and labour intensive can also be characterized as automated versus manual (Stein and Savage,1994).The following advantages favor the selection of a labour-intensive process:

Workers can sort materials that cant be mechanically separated

Work force is available for other assignments between jobs

Low capital cost for the process

The following advantages favor the selection of a mechanically intensive process:

High production rates

Greater worker safety

Smaller work force involve

2.2.4.2 Comparison of on site and off site crushing and sorting

Before implementing recycling program it is very important to decide whether use on site or off site crushing and sorting facilities. When contractors can store, recycle demolition materials on-site, on site crushing and sorting represents one of the most efficient methods of recycling, saving transportation, storage and some processing costs. For sites that can coordinate on site crushing and processing however financial benefits can be significant (Burgoyne, n.d.).Following table summarizes the key factors associated with a choice between on site and off site crushing and sorting facilities (Symonds, 1999).

On-Site Crushing and Sorting

Advantages of on-site crushing and sorting:

lower materials handling and transport costs

lower machinery capital costs

less transport disruption to surrounding areas (if recycled materials can be used on-site)Disadvantages of on-site crushing and sorting:

conflicts between site operations and space demands for materials and machinery

higher machinery operating costs per tonne of C&DW

more local noise and dust nuisance

construction may be delayed

Off-Site Crushing and Sorting

Advantages of off-site crushing and sorting:

Easier to reduce and/or mitigate adverse environmental impacts on surrounding areas

More practical to use a wider range of higher capacity equipment

lower machinery operating costs per tonne of C&DW

Easier to control quality of recycled materials

Possible to hold stocks, thereby making positive marketing of recycled materials easier.Disadvantages of off-site crushing and sorting:

Proper control of demolition process essential (to avoid arrival of unknown quality materials)

Higher materials handling and transport costs

Higher machinery capital costs

Fixed costs of recycling the site (land etc)

Table 2.2: Advantages and disadvantages of on-site and off-site crushing and sortingMaterial is most often processed in a sequence of sorting, crushing, sifting and a second sorting to yield a final product ready for use. As crushing and separating become very important steps of recycling, these two stage are dealt in detail under 2.2.4 and 2.2.5

2.2.5 Separation Process in Recycling

A necessary condition for the recycling of demolition waste is careful sorting and separating of the waste. However, the sorting of waste from demolition is a more complicated process (Lauritzen, n. d.). Most frequently different building materials are separated by manual sorting after a demolition. In Germany for separation process use either an air flow based or a water based separation device, from that majority of German recycling plants use air flow based separation devices although the water based technique provides the better quality (Schultmann, 2003). Before go to regular sorting techniques it is essential that hazardous wastes remove from the buildings before these are demolished (Anon, 2000). This enables:

(a) Contamination of the general waste stream to be avoided for recycling or land filling purposes and

(b) To ensure that the dangerous wastes extracted in this way are managed in an appropriate manner.

The main hazardous wastes covered by such separation at source are as follows: asbestos, lead piping or roofing material, other heavy metals, hydrocarbons, paint, and adhesives, wood treated with preservatives, contaminated earth and various materials containing PCBs (Polychlorobiphenyls) (Strufe, 2004).

There are two types of separation techniques as an air flow based or a water based separation device, whereby the majority of recycling plants use air flow based separation devices, than water based technique (Schultmann, 2003).

2.2.4.1 Water based separation

Wet separation techniques use water to separate lighter and heavier materials. . In some cases other substances are added to the water to increase the specific weight of the water and to change the point light materials flow up. Some water based separating devices use supplementary water jets or air to support the separation by density differences (Schultmann, 2003).As described by Schultmann, (2003) a general overview of the different kinds of water based separating techniques can figure out as below, which is differentiated by the four categories: Thin film separation, Jig separation, up current separation, Float and sink separation. Within these four categories several different devices are available based on the same techniques which each vary in detail (Schultmann, 2003).

Figure 2.2: Water based separating techniques.

2.2.4.2 Air flow based separation

Air flow based separating devices use the air flow to "blow away" light materials and to isolate the lighter non mineral materials from the heavier material materials. In general the airflow-based techniques are characterized by lower operating costs. But the resulting material separation is not as exact as with the wet techniques (Schultmann, 2003).

In airflow based separating devices there can see two fundamental systems such as "reverse air flow sorting technique" and the "cross air flow sorting technique. Cross airflow sorting has the advantage that the materials remain in the device for a much shorter time, which increases performance. In addition the geometric form of materials to be separated is much more important when separating waste materials. It is more in cross air flow technique than reverse airflow sorting and as a consequence, modern cross air flow sorting devices use the correlation of geometric form and the quality of material separation to achieve a better sorting.

Further another modification of the cross airflow sorting technique is the "exhaust of foreign matter". Instead of using a free fall system, the materials to be sorted lie on a vibrating conveyor belt that pre separate the light materials from the mineral fraction. The reverse air flow sorting techniques have increased their effectiveness of sorting by using Zig-zag separation devices, because the zig-zag form has the same effect as a succession of several single cross air flow sorting devices (Schultmann, 2003). In general, steps which the separation process consist can be shown as follow as the (Broere, n.d.; Hendricks and Pietersen, 2000):

Figure 2.3: Demolition waste separation process

2.2.6 Crushing process in Recycling

Crushing process involves two basic types of crushers are compression crushers and impact crushers. Compression crushers have two basic types of crushers Cone crushers and Jaw crushers. Impact crushers can be either vertical or horizontal (Hendriks and Pietersen, 2000).

Most recycling plants have both primary and secondary crushers; however some plants out put produce (e.g. aggregates) by primary crushing only. In plants with both levels of crushing, the primary crusher normally reduces the material down to about 3/4 in. The material then passes t h rough two screens that separate the aggregate into sizes, greater than and less than 3/8 in. The larger material is fed to the secondary c rusher where the maximum desired coarse aggregate size is set (Symonds, 1999). The best particle shape is usually achieved by primary crushing and then secondary crushing, but from an economic point of view, a single crushing process is usually most effective (Khalaf and Devenny, 2004).

In general, steps which the crushing process consist can be shown as follow as (Broere, n.d.; Hendriks and Pietersen, 2000):

Figure 2.4: Demolition waste crushing process

2.2.7 Demolition waste material, Origin, Ways of collection, Ways of sorting, Recycling process, Technologies and End market/products

When consider demolition waste materials recycling, its recycling techniques differ from materials to material including their origin, ways of sorting, ways of collection, recycling process, technologies and end markets/products and their applications. Since concrete, brick, wood/timber, metals (ferrous), metals (non ferrous), tiles, plastics and asbestos are commonly recycling materials in other countries and common materials can see in demolition waste materials, here for details studies has given priority for above materials.

2.2.7.1 Concrete

Concrete is one of most commonly recycling materials in other countries and its recycling techniques can be summarizing as following as:

OriginConcrete is the primary material for larger buildings in foundations, retaining walls, walls, roofs and floor construction (Leal, 2006).

Ways of collection

Recovered from concrete demolition sites it can be unprocessed or preferably, pre crushed by excavator breaker or mobile crushing machine (Leal, 2006). By reducing volume of concrete can reduce transportation cost and it allows for fewer loads.

Ways of sorting

In general following process is continuing in central sorting plants (Leal, 2006). Demolition materials are sent to sieving machine for pre sieving process. Then remaining sent to impact crusher and after that steel components are sorted by overhead magnet sorting and manually. Remaining RC building materials sent to sieving machine and then sort aggregate.

Recycling process

Followings are involved in recycling process:

In situ sorting by removing dressings and rebar.

Reduced by crusher and sorted by kernel size (Leal, 2006). Crushing can do either in situ or centralized.

Removal of metals by magnetic sorting.

By Rolling/Scalping removes large fractions.

Sizing according to standards by Sieve sorting.

As Nisbet et al. (n.d.) flow chart of basic recycling plant and production of aggregate can figure as follow as:

Figure 2.5: Flow chart of basic recycling plant and production of aggregateTechnologies

Plants for producing recycled concrete aggregates are similar to plants for production of crushed aggregate from other sources. They incorporate crushers, screens, transfer equipment, and devices for removal of foreign matter (Nibset, n.d.).

Recycled material ApplicationsRecycled concrete as reused in low value applications such as fill or road sub-grade is a well recognized application. Concrete can be crushed and ground to aggregate. The majority of it has to be sorted and used as fill (Leal, 2006). The value of in situ concrete in terms of recycling is low (Berge, 2000 cited in Leal, 2006). According to Leal (2006) Following are the applications of recycled materials.

Road base and construction fill Several authors has said that crushed concrete can be used as base fill in the construction of roads (e.g. Leal, 2006; Burgoyne, n.d.; Tam and Tam, 2006). The crushed material is used in place of lime rock. Crushed concrete may also be used as primary road surface material on unpaved roads in rural areas. The use of crushed concrete for driveways can also be practiced. The purity (i.e. presence of wood, dirt, other contamination) of the material may also be an issue (Leal, 2006). Aggregate in concrete - Aggregates can be recovered from concrete crushing process and used in the production of new concrete (Burgoyne, n.d.). According to (Townsend, 1999 cited in Leal, 2006) the addition of crushed concrete fines has been used, but the quality does not always meet the same results as when using clean sand and rock aggregate.

Drainage material - Crushed concrete that has been well screened of fine particles provides similar drainage characteristics as new rock or gravel. It can be used for drainage applications in construction. Other possibilities include septic drain fields and landfill leachate collection systems (Leal, 2006).

Producing concrete bricks and paving blocks (Poon et al., n.d.).

Market/End products RC-Frost protection material 0/32 - Base/Filter layer under surface or between foundation slabs

RC Concrete - SPLITT 0-8 - Self hardening Paving

RC Concrete - SPLITT 8-16 - Reinforcing of road and walkways, loose top coat

RC Concrete - SCHOTTER 16/32 - Drainage layer and basement wall protection

2.2.7.2 Brick

OriginStandard Bricks made from Clay, sand and light mineral materials which are wet mixed formed and kiln fired. Bricks are frequently coming from walls of building.Ways of collection

Collection ways are manual dismantling, cleaning and stacking. Brick rubble is lifted by sieve shovels with excavators, thus partial sorting is possible during collection (Leal, 2006).Ways of sorting

Rubble bucket lifting, sieving, magnetic separation and manual sorting are the most commonly used (Leal, 2006). Recycling process

It involves Crushing and sorting according to kernel size, separation from metal components (Leal, 2006).Technologies

Breakers and Crushers are identical. For that Mobile, semi-mobile, stationary crushing plants are more familiar (Montecinos and Holda, 2006).Recycled material Applications

Road base and construction fill Several authors has said that Crushed brick can be used as base fill in the construction of roads (e.g. Ozkan and Duzgunes, 2000; Leal, 2006; Tam and Tam, 2006). The crushed material is used in place of lime rock. The benefits of such reuse are often dictated by the local availability of lime rock deposits, as hauling costs are substantial. The purity (i.e. presence of wood, dirt, other contamination) of the material may also be an issue.

Crushed brick may also be used as primary road surface material on unpaved roads in rural areas. Clean, crushed brick as sports field lining and lightweight concrete addition and, with portions of flashes, mortars and ceramic, as crushed stone replacement or low density concrete aggregate.

Drainage layer

Recreational trail top coat

Mechanical soil stabilizer, inertness of material is well suited to this application

Market/End products

RC-Rubble 0/32 - Under layer or Filter layer for foundations

RC-Rubble 32/56 - Top layer for path and public space surfaces

RC-Rubble 0/X - Mechanical Soil stabilizer2.2.7.3 Wood, Timber

Origin

Wood C&D waste is largely recovered from old buildings and as forming material. Timber can be used to cover roofs as shakes, shingles or planks. As cladding it can be used as paneling or wattle, and as flooring it can be used as boards, parquet tiles or timber sets. The sheeting is produced as fiberboard, cork, chipboard or veneer.Ways of collection

It can collected either alone from a site or mixed with other C&D wastes. If the material quantity is large, in-situ shredding can help reduce transportation costs.

Ways of sorting

According to material quality, degree of contamination, size and type recovered wood wastes are sorted. Further sorting is carried out according to intended processing (Leal, 2006).

Recycling process

As Leal (2006) recycling of wood waste are involve following process.

Wood is collected onsite with or without foreign materials.

Sorting is done by hand and machine

Wood is shredded, sometimes onsite and sometimes with foreign matter

Further separation, like air blower and magnetic is performed on shredded material

Shredded wood is marketed

Technologies

Mainly used technology is Shredders in shredders following two forms are available

Single Shaft Shredder Specially designed high performance shredders are available specially designed for the wood processing.

Powerline - The Powerline shredder series are highly economical and specially designed for the production of substitute fuels (RDF) and offer a wide variety of innovative equipment and ancillaries. It guarantees a maximum rate of productivity. Low power consumption and low wear costs are the basis for the Powerline's economic efficiency.

In addition to that Saw, hand tools, etc is also used.

Recycled material Applications

Recycled wood can be ground into wood chips or wood flour and used to make composite or engineered lumber products, mulch, animal bedding, compost or many other products (Burgoyne, n.d.).

Market/End products

By studies of several authors identified following end markets from wood recycling (e.g. Leal, 2006; Burgoyne, n.d.).

Fuel - Germany has significant biomass generating capacity (ie: domestic wood pellet heaters) and Wood can be a green supplement in coal generators (Leal, 2006).

Engineered Wood - Production of various pressboards and fiberboards is possible with these wood fibers

Mulch or Compost Amendment - Cleanliness of the product is particularly important for such uses

Animal Bedding

In addition above end uses are identified by (Jackson et al., 2003; James, 2003; Orme, 2003; Anon, 2005).

Manufactured wood products

Alternative wood fiber-based materials (e.g., particle board, MDF)

2.2.7.4 Metal (Ferrous)

Modern building construction, industrial, commercial and institutional, and residential, is using metals for improved performance, durability and appearance (Nisbet et al., n.d.). Steel Demolition debris is very recyclable due to its lack of contamination by dissimilar materials (Burgoyne, n.d.). Scrap steel is almost totally recycled and allowed repeated recycling (Coventry, 1999 cited in Tam and Tam, 2006).

Origin

Steel is the most important structural metal and is used in all the structural components of a building from foundations (usually combined with concrete) to the roof. Steel used in structural cases is often unalloyed (Leal, 2006).

Ways of collection

The way of Collection is the removal of materials directly from a building. Large sections may be cut or shredded onsite before transport. When collected in conjunction with other materials such as concrete, brick, wood, plastic and others metals must be sorted out from other materials at a central processing site (Leal, 2006).

Ways of sorting

Density Separation

Manual separation

Magnetic Separation

Eddy Current Separation

Recycling process

Recycling operation involves Sorting and separating activities and Recycling operation itself. Sorting and separation activities include manual sorting and dismantling, cutting, flattening and shredding. Manual sorting and dismantling may be applied to products and materials with significant value. Cutting and flattening may be used to reduce the size of large homogenous metal items (predominantly iron, steel and aluminium items), thereby making them suitable for further handling and transport (Holm et al., 2002).

So that after onsite separation from concrete and other materials involves shredding and further sorting of reduced material and marketing it domestically or internationally to foundries. Further sorting will done using various methods including Magnetic sorting for ferrous fractions and Density separation to separate other metals using Eddy Current separators (Leal, 2006).

Both collected old scrap and new scrap from manufacturing is sorted with ensuring homogenous high quality materials. If steel is unsuitable for direct reuse it is melted to produce new steel (Tam and Tam, 2006).

Technologies

In Germany following two different steel production methods are used (Leal, 2006), each with different possible levels of scrap steel content.

The Basic Oxygen Furnace Method (BOF) (approx. 71 % of 2000 total production) works with a scrap iron employment between 20 % and 30 %.

The Electric Arc Furnace steel production method (EAF) (approx. 29 % of 2000 total production) is capable of employing 100 percent scrap metal in production.

The recycled content of EAF relies on the embodied energy savings of the steel created in the BOF. And the BOF infuses a greater supply of new steel in to service to provide for continued economic development (Crawford, 2001).


Recycled products are used for produce new steel

Market/End products

Processed or unprocessed scrap steel

2.2.7.5 Metal (Non ferrous)

A number of nonferrous metals have found wide application in the building industry. Aluminum is used in window framing as well as cladding. Copper, is used in wiring and as the main component of water distribution networks while lead piping was often used in older plumbing systems. Zinc is used in steel galvanizing as well as in brass alloys. Nickel is used in production of stainless steel. Other nonferrous metals are also used to produce various alloys and to modify / improve the properties of steel (Nisbet et al., n.d.). But in these study mainly focused on Aluminum material only.

Origin

Aluminium is a frequently used metallic material where light structures and as roofing or exterior siding material. Aluminium can be recycled after having undertaken adequate treatment and preparation without any loss in quality because its properties and characteristics are not affected even after it has been used in a product. The high value of the metal is maintained through multiple reapplication cycles with giving sufficient economic incentive for its collection and recycling into a similar or comparable product (Leal, 2006).

Ways of collection

Collection can done either onsite or during post collection of mixed wastes or mixed metal wastes. Aluminium, once reduced by crusher and shredder with mixed waste that can be effectively separated from a mix by eddy current separation (Leal, 2006).

Ways of sorting

Ways of sorting involves:

Separation from foreign materials

Magnetic separation

Eddy Current Separation (can distinguish alloys and non ferrous metals)

Density separation (dry and wet cyclonic)

Inspection and removal

Separation in melting

Recycling process

Recycling process for non ferrous aluminium involve following course of action (Leal, 2006).

Collection and recovery - Old and new scrap are collected and recovered by the metal trade or the refiners and remelters themselves.

Preparation and treatment - The scraps recovered are treated according to their quality and characteristics. Common treatment processes are for example sorting, cutting, baling or shredding. Turnings are dried and crushed. Free iron is removed by magnetic separators. Aluminium skimmings, a mixture of aluminium metal and aluminium oxide, are crushed or ground and air separated.

Charging - As a rule computer controlled selection and mixing of scrap types whose chemical composition is as close as possible to that of the required alloy.

Melting - Various furnace types are available for melting aluminium scrap. In Germany, scrap for the production of casting alloys is commonly melted in rotary furnaces under a layer of liquid melting salt (flux). Producers of wrought alloys prefer open hearth furnaces in varying designs.

Refining - The alloy production in rotary furnaces is followed by a refining process. The molten alloy is fed into a holding furnace (converter) and purified through the addition of refining agents.

Quality control - Every single charge of the furnace is tested in the plants Laboratories with modern computer controlled analytical technology equipment and, provided that the result is positive, receives a certificate.

Casting - The molten aluminium is either cast into ingots or transported in liquid form to a foundry. The ingots weigh, depending on the shape of the mould used, between 4 and 25 kg. Liquid aluminium is filled into pre-heated thermos containers and transported to the foundries, where the liquid metal is filled into holding furnaces and processed immediately.

Homogenising - Heat treatment of extrusion billets in special furnaces in order to obtain a metal structure which is appropriate for further processing and to remove residual stress of the casting.

Technologies

Shears, Shredders, Magnetic and Eddy Current Separators, Furnaces/melting, etc are the commonly used technologies. (Leal, 2006; Tam and Tam, 2006).


Once sorted products can be sold to scrap metal merchants or directly to end-users by melting (Tam and Tam, 2006).

Market/End products

Scrap aluminium from product manufacture or at the end of a product's service life becomes a secondary raw material which has markets world-wide. Primarily two kinds of firms purchase aluminium scrap.

Refiner - Produces casting alloys and deoxidized aluminium from old and new scrap and supplies them in the shape of ingots and liquid aluminium.

Remelter - Produces wrought alloys from mainly clean and sorted wrought alloy scrap and supplies them in the shape of rolling slabs, extrusion billets or master alloys.

Casting alloys - Casting alloy, standardized or produced according to specific customer requirements, are supplied in ingot or liquid form to foundries which cast them into high quality components. Typical applications are cylinder heads, engine blocks or gear boxes in automobiles, components and parts in the mechanical and electrical engineering industries, casings for household equipment etc.

2.2.7.6 Tiles

Origin

Tiles are Clay, Sand and Metal oxides are wet formed and kiln firedWays of collection

Ways of collection is Onsite collection and here required careful labour intensive removal.

Ways of sorting

Separation of non frost resistant material, Wobbler feeders, sifting

Recycling process

Tiles are crushed, often along with brick and concrete. The mixtures are then sorted according to kernel size (Leal, 2006). Concrete roof tile can be salvaged for reuse. Damaged tiles can be recycled by recyclers and combined with other inert materials such as brick, asphalt and concrete (Burgoyne, n.d.).Technologies

Main recycling plants technologies use to crush tiles are practically identical as those used to crush brick and concrete. Recycled material Applications

Crushed tiles with portions of brick, mortars and stones and concrete may be used as gravel and crushed stone replacement Applications include: noise protection barriers, soil stabilizers, cover material and backfill of excavations. Followings are recycled tiles applications.

Use as a filling material

Use in road base material

Use as a hard core material

Market/End products

Crushed tiles, in conjunction with brick and concrete make for useful underlay and drainage material. Similar to brick and concrete the largest market for crushed recycled tiles (in mixed form) is in road construction (Leal, 2006).2.2.7.7 PVC/Plastics

Origin

PVC Pipes, Cutters, PVC floor mats, PVC roof sheets, PVC plastic windows, roller-type shutters and doors profiles, Shutters and blinds, Paneling and cladding, Ducts for electrical cable etc (Leal, 2006).

Ways of collection

According to Leal, (2006) studies identified that, PVC floor mats, PVC roof sheets, PVC plastic windows, roller-type shutters and doors are collected over a country wide by separate collecting system and supplied to the processing in recycling plants.

Ways of sorting

Manual sorting is the ways of sorting

Recycling process

Recycling process mainly involves Flooring removal, Material Sorting, Recycling system, Shredding, Shredded Chips (30mm).

The sorted old PVC floor mats are cut up first into chips measuring at the most 30 millimeters. After a magnetic metal separation process, a hammer mill releases the chips from adhering screed and adhesive remainders. Thereupon they are separated in a sieve jigger from these reduced impurities. For following fine grinding the PVC material with liquid nitrogen is cooled on a temperature of minus 40 C. By the cooling the PVC chips briefly embrittled and finely ground into particles with a diameter of no more than 0.4 millimeters (Leal, 2006).

Technologies

There are two principal ways to recycle (COWAM study, n.d.a,):

Mechanical recycling: PVC waste is ground into small pieces that can be processed into new PVC compounds ready for extrusion or lamination.

Feedstock recycling: PVC waste is broken down into its chemical constituents, which can be used again to make PVC or other materials.

In PVC recycling following mechanical recycling Technologies are involve (Plinke, 2000):

Pre-sorting

Granulating: post-consumer plastics are ground and washed.

Flotation tank: if the different kinds of plastics are not sorted, they are separated in a flotation tank (density of the different plastics).

Drying: clean plastic pellets must be dry because dampness decreases the quality of the end product.

Melting: heat and pressure melt the plastic in an extruder (each type of plastic has a different melting point).

Filtering: the molten plastic is forced through a fine screen to remove any contaminants that may have eluded the washing cycle.

Pelletizing: the strands are cooled and chopped into pellets to be sold.


The PVC recycled is used in the production of fillcasing in cables, hoses and signfooting. Recycled pipes are used together with virgin PVC as equivalent material (Montecinos and Holda, 2006).

Market/End products

Although the market for PVC recycling is still limited following markets can identify (Montecinos and Holda, 2006).

PVC producers.

2.2.7.8 Asbestos

Origin

Asbestos is the name for a group of naturally occurring, fibrous minerals. White asbestos (Chrysotil) and blue asbestos (Krokydolith) were most frequently used. Since asbestos is extraordinarily heatproof and very chemically stable, it was used for the production of various products. As Leal (2006) it was applied in two forms.

Firm fiber (non-friable) connection asbestos was used in cement products, pipes, and other building materials. It was also widely used in brake linings. Such materials are stable and present fewer risks.

Weak fiber connection (friable) asbestos was often in the form of asbestos sprayed on as fire protection. It was also however used in asbestos boards; pre cast plates, electric insulation, noise insulation and heat and vapour protection.

Ways of collection

In order to make possible and easy processing of the usable components of building wastes as well as the normal disposal of the asbestos contaminated Components should collect carefully.

Ways of sorting

Materials are further separated which are cleaned and those to be disposed. Sorting is important in order to ensure appropriate treatment for each particular type of asbestos form.

Recycling process

Loading, Shredding, Chemical bath (dewatering), Furnace (the rest of the moisture removing), Rotary kiln, Ejecting, Sealing are the main steps in Asbestos recycling process.

Technologies

At present chemical, thermal and mechanical procedures for asbestos fiber destruction are used for asbestos recycling (Leal, 2006). Sprayed asbestos and asbestos types of dust which are preferable to dispose should solidified or stabilized by means of suitable inorganic bonding agents, like glass, at the point of accumulation. Depending upon the condition of the asbestos contaminated wastes, different methods of the surface treatment or the packing are required.

Chemical procedures for the chemical treatment of asbestos contaminated wastes largely use hydrofluoric acid. Byproducts of this neutralization process include calcium fluoride, metallic oxides and hydroxides as well as silica. Use of the byproducts of asbestos treatment are directed at cement and concrete production, as fluxing agent and as secondary raw material for hydrofluoric acid Thermal procedures include

Vitrification of asbestos contaminated wastes involves melting them at temperatures around 1400

Asbestos-free glass granulates are the process output.

Asbestos minerals are converted in special rotary kilns at temperatures by 800 C into other minerals, such as forsterite and olivin.


Recycled materials mainly use as a filling material after mixing it with soil

Market/End products

End products are filling materials.

2.2.8 Commonly used Recycling Plant Technology

According to Symonds (1999) there is a wide range of possible technical solutions which can be applied to demolition waste recycling, from simple mobile crushers to fully integrated fixed Demolition Waste recycling centers. These technical solutions are may be inappropriate to the circumstances they face and the mix of waste requiring to be processed.

Mobile facilities are set up on larger demolition sites, so that the demolition waste can be processed on site. In stationary facility consist with its own complex configuration. Due to this by processing building waste in stationary facility it is possible to produce high quality recycled materials than mobile facilities (Schultmann, 2003).

In following figure shows appropriate techniques related to circumstances (Symonds, 1999).

Figure 2.6: Appropriate recycling techniques

Three broad levels of recycling technologies and their applications are as follow as:

(i) Level 1, which comprises mobile crushing and sorting plant, and is only really suited to the processing of inert C&DW;

(ii) Level 2, which also has metal removal and more complex sorting and sieving facilities, and is therefore capable of dealing with mixed (mainly inert) C&DW; and

(iii) Level 3, which adds hand sorting, washing plant and facilities for other C&DW streams (such as wood) to Level 2 plant, and can deal with any (mixed and contaminated) C&DW if required.

However, as a general observation it is fair to say that Level 1 technology is mainly associated with low levels of recycling, Level 3 with high levels, and Level 2 with an intermediate position (Symonds, 1999).

2.2.8.1 Demolition waste processing equipment

Generally, Recycling Plants consist only of manual pre-sorting system, crushers; manual sorting that removes contamination, conveyor belts and screenings (Angulo et al., n.d.). Symonds (1999) stated that Deutag Remex (Or Remex) is the leading operator in Germany at demolition waste recycling centers and it shows common recycling process, which is used in most recycling plants(Symonds, 1999). The equipment includes crushers, sieving and screening equipment, magnetic separators, air classifiers, manual and mechanical sorting, and other materials handling processes.

According to Symonds (1999) in Remex recycling operation can see following process:

The incoming inert fraction is weighed and inspected, and placed in to one of a series of separate stockpiles such as Broken bricks and tiles, Reinforced concrete, non-reinforced concrete, Mixed C&DW, etc.

Then broken bricks, tiles, reinforced concrete and non-reinforced concrete are screened through a pre-sieving process to remove the 0-45mm fraction (divided into 0-4mm and 4-45mm).

The remaining material goes to an impact crusher. Material coming out of the impact crusher passes through a magnetic separator to remove ferrous metals before being sieved to divide it into 0-45mm and >45mm. The >45mm fraction is placed onto a temporary stockpile for re-crushing, while the 0-45mm fraction is sieved into sub-fractions of 0-4mm, 4- 8mm, 8-16mm, 16-32mm and 32-45mm. These sub-fractions can be re-combined into mixes defined by the end user, or into proprietary (branded) mixes.

Instead of sieving into the sub-fractions described above, the 0-45mm fraction can be passed through an air classifier, washed, passed through a further metal separator and screened through either a vibrating screen or a free-fall screen. This produces a range of washed, sorted and quality-graded materials. Any oversize materials (which are more common with jaw crushers than with impact crushers) can be sent back to the crusher for re-processing.

In the Remex system, mixed C&DW is generally subjected to hand sorting even before it is screened and passed through a magnetic separator for the first time. This is followed by further manual (or in some cases automated) sorting to remove plastics, paper, wood and other non-ferrous metal wastes.

The mixed C&DW is then passed through a jaw crusher and magnetic separator before being passed through an air separator which removes light materials (small pieces of paper and plastics which escaped the earlier sorting processes and the 0-4mm fraction of the inert material. The 4-45mm fraction can then be sieved or screened, as with the brick, tile and concrete waste.

Following figure is a relatively sophisticated mobile plant fitted with a jaw crusher. Fixed plants also very similar to this and it have higher processing capacities with providing hydraulic legs rather than crawler tracks or wheels.

Figure 2.7: Cross section of a Jaw crusher mounted on a mobile chasis with associated Equipment

The choice between an impact crusher and a jaw crusher may vary according to operators and usage to which material will be put. Impact crushers produce an aggregate with a smaller range of sizes. Even though they are substantially cheaper to buy on a size-for-size basis, when considering hard materials like some reinforced concretes their running costs are much higher (Symonds, 1999).

Impact crusher produces a more consistent and predictable aggregate, with sharper edges on the individual granules. It use a high speed rotor inside a container into which the material to be crushed is fed. There are typically four or six hammer plates mounted on the rotors which break the material against face plates set at operator-determined positions on the inner surface of the container. The cutting action is very like that on a conventional cylinder lawnmower (for cutting grass). The throughput is greatly affected by the clearance between the rotating hammer plates and the fixed face plates, and the rate of wear on the plates varies greatly according to the hardness of the material being processed (Hendriks and Pietersen, 2000).

Jaw crushers are typically shaped like a wedge, in which one of the faces moves relative to the others, producing a chewing action which grinds the material into progressively smaller pieces as it passes towards the narrow end. Material is fed in at the wide end (the top), and falls out at the narrow end. The narrow end can be set to a range of openings to determine the nature of the resultant material. In general impact crushers tend to be designed for higher throughputs than jaw crushers (Hendriks and Pietersen, 2000). On-site and off-site sorting and processing is accomplished by manually, semi manually and stationary machines: these are consisting with Manual sorting lines, Shredders, Crushers, Aggregate sifters, Water Based Density separators, Magnetic separators, Eddy current separators, Air blower separators (Montecinos and Holda, 2006).

Equipment

Equipment selection is based on ruggedness, processing capacity, maintenance and operating requirements, ability to process feedstocks of widely varying composition, and energy consumption (Stein and Savage,1994). The equipment most commonly employed in the processing of demolition debris recycling can listed as follow (Stein and Savage,1994; Peng et al., 1995).

Size reduction equipmentScreening equipmentOther equipment

Hammerill (e.g. wood hog)

Hydraulic breaker or jackhammer

Impactor

Jaw crusher

Rotary shear shredders

Screw shredders

Stump grinder Disc screen

Grizzly screen

Trommel

Vibratory screen

Reciprocating bar

Air classifier, air knife

Magnetic separator

Belt conveyor

Steel pan conveyor

Table 2.3: Demolition waste processing equipments

2.2.8.2 Demolition waste Processing flow diagram

Demolition waste processing can summarize as following showing method in figure (Peng et al., 2005);

Figure 2.8: Demolition waste Processing flow diagram 2.3 Economics of the recycling of Demolition waste

When considering a recyclable materials, three major areas needs to be taken in to account such as economy, compatibility with other materials and material properties ( Mindess et al., 2003 cited in Tam and Tam, 2005). Recycling economics mainly refers to assess the costs associated with a recycling program including the cost of collecting, sorting, screening, crushing, and transportation to the crushing plant, as well as the cost of transportation to the place of use (Khalaf and Devenny, 2004). This can be done firstly detailing the quantity and composition of materials found in waste stream and secondly evaluating the costs associated with recycling programs for the target materials. This involves the capital cost and operating cost of recycling plants and labour cost (Symonds, 1999). If recycling program is off site operation it should pay careful consideration with transportation costs also.

Economic feasibility of a recycling program depends on whether the added costs (increased time, effort, and equipment) associated with the recycling program are less than the avoided costs (tipping fees, surcharges, labour, hauling fees, maintenance, permit fees, and taxes) plus sales revenue. If the added costs exceed avoided costs plus revenue, the operation should not be undertaken (Anon, 2005).

Therefore it is critical that careful economic analysis be performed to determine whether a project should include a recycling program. Costs of program have a greater impact on the feasibility of waste recycling and cost savings motivates the demolition industry to implement recycling program (Leigh and Patterson, 2004). The value of the final marketable waste or market price is determined by the cost of competing products at the point of application. This free market price is based on the material cost, processed cost, transportation cost and profit and free market price is equal to sum of above factors (Anon, 2005).

Material costs include the cost of procuring the raw waste stock from the generator.

Processing costs generally depend on the sophistication of the equipment and the amount of labour required handling, process, and prepare or package the products. Overhead costs, such as administrative costs, should also be computed in the processing cost.

Transportation costs depend on the distance from the site of processing to its market. If it is off site operation, distance from original demolition site to processing center and distance from processing center to market also involve.

Profit is set by the processing facility to cover the risk involved in operating a waste processing facility.

Once the free market price is calculated, this information can be used to compare the products with those produced with virgin materials. The level of economic analysis will depend on the scale and scope of the recycling operation (Anon, 2005). If the extent of the operation is not much large prepare waste materials by sorting on-site, and then the analysis easily involved determining:

(1) The cost of labour and equipment needed to separate the waste (added costs),

(2) The hauling, permit, and tipping fees of disposing of the material in a landfill (avoided costs), and

(3) Any revenue expected from sale of the debris.

If the added costs are less than the avoided costs plus the revenue, then it would be cost-effective to separate the waste and sell it to a recycling facility.

While many Demolition waste materials are suitable for recycling, there are external factors that influence the spread of Demolition waste recycling. The value of recycled and salvaged goods in the marketplace, labour costs for removal, sorting and processing and relative disposal costs etc all factors play a role in calculating cost for recycled goods (Anon, 2005). Recycled and salvaged goods must be price competitive and perceived to be as desirable as or even more desirable than products produced from virgin materials. Competitive pricing is impacted by subsidies, incentives on virgin materials, and market demand.

When evaluating economic feasibility of recycling demolition waste using three types of processing facilities, it can say that (Symonds, 1999):

Level 1 is the lowest cost approach, consisting of mobile C&D crushing and screening machinery which are brought to a demolition site and processed.

Level 2 represents facilities typically including a large tipping floor for hand-sorting of large and valuable items as well as crushers, conveyors, screens, magnets and other equipment such as air classifiers. Therefore level 2 shows higher cost approach than level 1

Lever 3 technologies includes the traditional demolition waste recycling equipment available in Level 2 plants, as well as equipment that enable further processing of recovered materials such as washing systems.

Costs for disposal of demolition debris have the most impact on demolition debris recycling and evaluating economic feasibility. So that Tipping fees can make or break efforts to recycle (Leigh and Patterson, 2004). If recycling costs more than disposal, then there will always be a very good reason not to recycle. But if recycling is cost-competitive or less expensive than disposal, then recycling should be considered as part of every job. Symonds (1999) studies demonstrate following relationships between disposal, processing and value of recycled product.

Disposal of C&DW Value of Recycled Product Outcome

Cheap and

legal Low Processing costs must be low enough to compete with landfill if any recycling is to occur. Transport costs are very important.

(For inert C&DW, this is typified by Level 1 technology).

Higher than

disposal

costs Processing costs can rise above those of Level 1 technology.

Competition among processors becomes more important as a way of containing costs for holders of waste.

Expensive

but legalLow Processing costs (but not the prices received for recycled products) can rise above those of Level 1 technology, and these rises can be passed on to holders of waste (i.e. owners of buildings), thereby allowing more sophisticated recycling.

Competition between demolition contractors and between processors becomes more importan

recycling of demolition waste and strategies

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