Sustainable waste management is become a main concern that has grown out of wider recognition and economic development are threatening a progressive degradation of the earth resources. The construction, maintenance and use of building impacts on environment and is contributing significantly to irreversible changes in the world's climate, atmosphere and ecosystem. Sustainable waste management is to protect human health and the environment by producing less waste and using it as a resource wherever possible.
KEYWORDS: construction industry, recycle, reuse, sustainable, waste management.
INTRODUCTION
The aim of this research is to manage the construction waste with sustainability. Sustainable waste management means less reliance on landfill and greater amount of recycling and composing of the product. The construction industry research and information association have reported that an estimated 72.5 million tones of construction and demolition waste are produced annually. This is around 17.5% of the total waste produced in the U.K. 13 million tones of construction materials are delivered to sites in the U.K and thrown away unused every year.
It is required to provide for a waste management and recycling plan for construction and demolition projects for all new buildings and refurbishment of existing building with intent to minimize the generation of waste due to construction activity and manage the generated waste in a sustainable manner.
Management of construction waste is a serious concern in the country given the high phenomenal growth in construction industry. It has serious consequences due to the increasing quantum of demolition rubble, shortage of the dumping sites, increase in transportation and disposal cost and various associated environmental issues. The construction waste includes debris, concrete, steel and other metals, plastics, packaging and paper products etc. there is need to move toward a more sustainable use of resources. Following figure show the waste produced by sector in the U.K
Figure 1. Waste produced by the sector in the U.K (Bendall, 2005)
As can be seen from figure, waste arising at these levels constitutes a significant environmental problem.
BACKGROUND
The need for adequate treatment and disposal of waste by man arose as population moved away from disperses geographical areas to congregate together in communities. The waste generated contained a range of materials such as broken glass, rusty metal and food residue. Such waste was dangerous to human health. This led to an increasing awareness of the link between public health and the environment. A lot of environmental action programme were held to minimize the waste. Sixth Environmental Action Programme focuses on sustainable management of natural resources and waste.
The concept of sustainable development has developed from the 1992 United Nations Rio Conference on Environment and development through to the Johannesburg World Summit on Sustainable development (Williams). The concept tries to make a balance between continued economic development and achievement of higher standards of living for today's society and for future and also to protect and enhance the environment. Sustainable development promotes development by encouraging environmentally friendly economic activity. These activities make the better use of land and buildings, improved transport efficiency and waste minimization. European Union has developed a series of directives and programmes which has the key objectives of minimizing the amount of waste.
Waste has many types like agricultural, business, commercial and industrial, construction, hazardous, wood etc...
CONSTRUCTION WASTE
Construction waste consists of material produced directly or incidentally by the construction or industries. Construction waste can be divided into three categories material, labor and machinery waste. Material wastage is of more concern because most of the raw materials come from the non -renewable resources. In the construction there is no conventional raw materials are available without causing some degree of environmental impact. With economic development there is an increase in the volume of construction and demolition activities. The resulting rising amount of construction and demolition waste has caused serious problems both locally and globally (Ofori and Ekanyake). A number of researchers have highlighted the potential benefits in preventing or reducing construction and demolition waste. By appreciating the principles of handling and using materials on site, attitudes to prevent waste can be developed and construction process can be managed more efficiently .Some studies have focused on the recycling potential of construction waste and demolition materials. Few studies however have compared waste minimization and recycling strategies in embodied energy and cost terms.
Material Waste in the Construction Industry
The completeness and reliability of embodied energy analysis methods is crucial to the validity of the application of embodied energy data to scenarios such as waste minimization. This also applies to the assessment of the direct and indirect costs associated with recycling and disposal strategies. The selection of one strategy over another could be determined by small variations in the embodied energy and cost values. (Willson)
Figure 2 shows the waste streams for construction and demolition processes. The winning of raw materials is show on the left of the diagram. The manufacturing stage refers to transformation of basic materials into building materials and products, along with initial processing stages (for example, metallic ore refining). There may be several transactions between industries at this stage. The construction stage refers to the assembly of materials and products to form the finished building. In the building use stage, construction services may be used in facilities management for maintenance and refurbishment of existing buildings. The demolition stage refers to the final and total disassembly of the building. The horizontal arrows depict the flow of materials with or without recycled content. The curved arrows represent re-use or recycling processes, under two categories:
Figure 2: Flow of materials, product and wastes for construction and demolition activities including closed and open loop recycling. (Treloar, 2003)
(1) Closed loop recycling (i.e. within that industry or building life stages); and
(2) open-loop recycling (i.e. between industries or building life stages).
The use of recycled materials at any stage displaces requirements for new materials, and may save considerable cost, natural resources and embodied energy.
Recycling schemes and effective source separation require active participation of a large share of the population. The time spent on source separation in households has been identified as the dominating cost in several cost-benefit analyses (CBAs) of recycling challenging the sustainability of such schemes. To become truly sustainable they need to be perceived as meaningful by consumers, companies and organizations. Source separation also needs to be simple and rapid to carry out in practice. At the same time, the waste collection must be safe, its economic cost must be reasonable and the cost must be covered in a sustainable manner. Significant potential for environmental improvements exists in some recycling processes, possibly because they are relatively new and have not experienced the same external pressure as, for example, incineration and landfills. Life cycle assessment and similar environmental assessments are based on data that reflect current performance and might under-estimate the long-term environmental benefits of recycling, weakening the environmental arguments for recycling of materials. Waste management is affected by policy instruments of various kinds: legislative (landfill bans, emission limits, etc.), economic (taxes, differentiated waste collection fees, etc.), information, and physical improvements (e.g., curbside collection). The recent commission on waste-incineration tax recently found that no decision-support tools were available that could model possible outcomes and evaluate the related environmental impacts of such policy instruments. It is even more difficult to analyze how the different policy instruments interact. A policy instrument that is well devised, logical and effective in theory might still be ineffective when applied in an institutional context.
Site observations
Some of the most important discussions covered waste types, waste handling methods, programming, project types, cost implications, education and human influence on waste management. Observations made in relation to waste management during site visits noted signs and notices, bin contents and waste handling procedures, control issues and site layout.
The waste handling method on-site began at the work area, where wastes were stockpiled and then removed by labourers daily into a small collection bin suspended by the site crane at the edge of the working deck. The crane was used for approximately one hour per day to carry out this clean-up operation. Discussions indicated that this method of waste collection must be analysed closely prior to implementation, to ensure that a particular type of project was compatible with waste handling methods proposed.
Disposal of the four key material types were analysed in detail:
Timber: Waste occurred from work undertaken on the materials to make them suit the required shape and size of the formed concrete, and due to rough stripping methods. Good planning by the sub-contractor to make formwork fit with minimal modification and better care during the stripping of formwork would have contributed to reducing waste. Waste timber products generated by formwork were deposited into bins at the work area since there was easy crane access to place bins onto the working platform. Thus a high proportion of material was able to be separated for recycling. Problems included the careless contamination of timber with foreign substances such as masonry or other waste at the ground floor level. The whole load of timber then became non-recyclable and forced the waste contractor to dispose of large quantities of timber waste as general waste.
Masonry and plasterboard: These were used for partitioning works. During construction, a majority of the masonry blocks ordered and used were standard sizes available from the manufacturer, consequently waste was avoided to a large extent. Waste during construction occurred when blocks remaining from various work areas were left over and no effort was made to collect and use them elsewhere. Often these were simply disposed of during cleanup.
Other minimal waste occurred through broken blocks or due to unusable off-cuts. Plasterboard was susceptible to damage both during handling and also once in place. Planning of sheet sizes required at various stages during the project minimised waste and was carried out by the Project Manager in conjunction with the plasterboard sub-contractor and plasterboard manufacturer. Although a bin was provided to receive concrete and masonry waste, no materials of this type were successfully separated. All concrete and masonry waste on this site was disposed of as general waste. Plasterboard waste was collected in stockpiles near the work areas. During the cleanup process, the waste was deposited into suspended crane bins as described for metal products. Due to the large volumes of this material segregation was relatively simple. Therefore a substantial amount of plasterboard waste was successfully separated. No recycling opportunities existed for plasterboard on this project as the manufacturer did not have the facilities to reprocess this product.
Paper Product: A large amount of paper packaging of goods on-site had to be appropriately disposed of. Packaging itself was not significant during the product use phase as it was generally intended for disposal and acted as a protection to goods during handling. Paper products derived from packaging were to be deposited into a bin provided by Visy Board at the ground floor. Again, sorting difficulties on each floor meant that very little paper products went into the designated bin and were mainly disposed of as general waste.
Metal: Metal waste was mainly derived from reinforcement, steel partition framing and roofing off-cuts. Reinforcement waste was minimal and primarily resulted from miscellaneous spare items left after the completion of the works. Metal roofing waste was due to off-cuts and modifications made to sheeting materials and flashings to suit roof penetrations and geometry. Metal stud waste was attributed to the requirement of size modifications to suit the application. The metal scrap bin was centrally located at the ground floor level between the two apartment buildings. At rubbish collection time, all refuse was collected into one suspended container at each floor level by the crane. Consequently loading work was hurried in order to minimise crane time, and various waste streams could not be sorted prior to placing in bins. Therefore, only large and easily separable metal waste was placed in the scrap metal waste bin. Valuable waste such as
copper and aluminium was retrieved and taken off-site by the subcontractors and did not contribute significantly to metal waste. The remainder was disposed of in the general refuse bin.
Waste types contributing to a majority of the bulk refuse were plasterboard and formwork scrap. When building products were inexpensive, as was the case with plasterboard, little consideration was given to waste minimisation. In the case of formwork, which was not a cheap product and yet still produces high quantities of waste, the reduction of waste required closer supervision. Human influence on the success of a waste management plan was apparent as it was the work-groups which had the final control over the waste handling process. The introduction of Waste Management has been viewed in a light similar to Quality Assurance and Workplace Health and Safety, which are now generally accepted but each required time before becoming completely effective. Generally, people were willing to contribute positively to the environment but it has been difficult to change habits and culture. During discussions with site management, it was mentioned that the younger generation seemed to accept waste minimization readily whereas the older generation were a little more difficult to convince. Perseverance and continually updated training will, some would hope, influence construction workers positively in due time. Also of influence may be stricter contractual obligations with possible penalty charges for non-compliance. Alternatively, a system promoting a spirit of competition and enthusiasm using incentives may provide the appropriate motivation.
Colour coded notices were placed at various strategic locations on the site including lunch room walls and the notice boards. However, the effect of waste management notices and signs was lost amongst other general information. Possibly, brighter displays isolated from general news and advertising bulletins may have attracted more attention. The notice itself was clear and easy to understand and should have served as a good reminder of the waste separation requirements established on site. The main waste bins had easily identifiable signs clearly displayed on the appropriate bin at most times. Occasional problems occurred with the correct labelling of the bins as the signs were removable and were shifted around when the bins were picked up by the trucks. Greater care should have been taken by all people involved in handling the bins or depose waste, to make sure the correct sign was clearly displayed.
Upon examination of the bin contents it became apparent that there was a general disregard for placing the rubbish in the proper bin. General rubbish contained materials which could have been separated with minimal effort. The difficulties of controlling waste segregation at all times became apparent during the distribution of the questionnaires around the site. Work was carried out throughout various areas of the project and workers were difficult to locate. Therefore, it was difficult for one person to oversee the compliance of waste separation and workers' attitudes were such that they could not be relied upon to monitor themselves. Waste management is the collection, transportation, processing, treatment, recycling or disposal of waste materials to reduce their adverse effects on human health. The management of waste in developing countries differs greatly from what is done in advanced communities and also from urban to rural and from residential to industry settings. Problem of waste management in developing countries include less effective, garbage trucks, low technology and unplanned and haphazardly constructed sprawling. The sustainable waste hierarchy is used to manage the waste properly.
Waste Hierarchy
Reduce: Reduce the amount of waste produce through careful resource management
Reuse: Reuse wastes as useful it.
Recycle and Compost
Recovery: Sustainability recovers energy from waste where possible by utilizing energy from waste technology.
Crushing and reusing concrete on sites eliminate the transportation and landfill disposal and redirect waste into a new project. Recycling concrete for reuse on or off site reduces waste and redirect reusable materials. The use of the indigenous materials reduces transportation distances and the associated environmental impacts. Transportation methods such as barging further reduce environmental impacts.
CONCLUSION
Managing construction waste is difficult and challenging. Some waste management techniques are used to manage the waste. The waste management techniques which rely on recycle and reuse of material has proven to have economic benefits for the construction industry. The long term benefits of a more sustainable approach to waste are not just recycle and reuse but also environmental. Design to minimize waste generation, increase the efficiency of the production process, and recycle wherever possible to produce materials and energy. Waste can be reducing with procedure of separating waste by products of construction but educated staff who has maximise knowledge and capacity to reduce waste and increase recycling.With the use of the sustainable hierarchy a waste can easily manage and reuse or recycle for the future use but also cost saving will realistic aim if new resources are created from the waste.
