Construction & Demolition Waste
The growth in the construction industry triggers waste production to exponential levels. The waste generated from the construction industry is commonly called as Construction & Demolition Waste or C&D waste. Most of the waste materials in construction industries are non-biodegradable and inert materials.
Construction waste materials are heavy, dense, bulky in characteristics and it needs more storage space and cannot follow standard waste disposal methods. ‘Reduce – Reuse – Recycle‘ are the most commonly adopted principles for waste management in the construction industry (also in any other waste management sector).
The gap between demand and supply of building materials such as fine aggregate and coarse aggregate in construction fields, especially in road construction is increasing day by day. Construction industries in India generate an average of 10-13 million tons of waste per year. By recycling the aggregate materials we can fill the gap between demand and supply, and also reduce the cost of production.
Objectives of Construction & Demolition Waste Management
The waste management system should always hold up the principle ‘Reduce, Reuse, Recycle’. The waste management strategies should be developed from the project planning stage itself. The prime objectives of waste management are; to reduce the amount of waste materials which are going to landfill or unwanted material disposal sites and to create useful resources from it.
Choose the materials wisely and don’t procure excess or unwanted materials for a construction project. The surplus amount of materials later on turns into waste and it also increases the overall cost. It also adds up to cost of disposal of waste. In transportation industry, the amount of cut and fill required is carefully planned to avoid any excessive excavation. This will avoid virgin material going into landfill.
Materials which are good in quality and undamaged can be reused for other construction purposes. So identify these materials and take advantage of that. Sometimes excess excavations are shared among other nearby projects if there is a fill requirement. Although, this will require continuous communication between stakeholders and upfront planning.
Different useful construction materials can be produced from construction waste by recycling it. For example, in road resurfacing projects, the bituminous layers are carefully scrapped and sent for recycling. The risk in waste disposal can be considerably reduced by recycling the waste materials.
Classification of Construction & Demolition Waste
While we consider the global construction waste statistics, the contribution of C & D waste by major construction industries are as below,
|Project Type||Percentage of C & D waste generated|
|Tunnel and Infrastructure||8%|
Construction wastes can be classified into following four major categories depending on the nature of waste generated.
The waste materials are re-used based on the following criteria, such as quality, dimension and the amount of contamination. Bricks, timber, roof tiles, glass etc. are possible materials that can be reused. Also these materials can be sold outside and can make a revenue source. Main advantage of this method is we can save resources.
Most of the waste materials are recyclable and other useful products can be made. Concrete, metals, plastic, timber, glass etc. some of the recyclable materials. A major drawback in these fine aggregates products are, it consumes more water than conventional fine aggregates. Metals (Including steel bars), plastic (PVC), glass can be recycled by melting it.
The waste management system predominantly focuses on recycling principles. Recycled aggregates can even be used for road construction. For example, during the demolition of flats in Kochi, the concrete debris of volume 7620 tons was later crushed using the machine called Rubble master into 6mm to12mm sized aggregates.
Every construction site holds up some amount of unwanted waste which is not useful. Sometimes demolition debris is also categorized into unwanted waste. These waste materials are commonly used for land filling purposes.
Contaminated water and spoil, fluorescent lamps, oils, solvents, materials, asbestos materials, PFAS etc. comes under hazardous waste and can’t be disposed of in usual way. These types of waste should be disposed of as per the environmental laws and regulations.
Common waste materials formed during construction and demolition are listed below,
- Cement concrete
- Steel rebars and metals
- Plastics and formwork members
- Card boards, Gypsum board etc.
- Stones and other ceramic materials
- Bituminous materials
- Other materials like fiber materials, asbestos, glass, electrical and wiring etc.
Construction & Demolition Waste Disposal
The construction materials are usually inert in nature and there is no impact like chemical or biological pollution to the environment by construction or demolition debris. However, in some projects, waste from excavation or demolition can be contaminated with chemical or biological contaminants. These will require further testing and treatment before disposal. Eg: PFAS.
The demolition waste materials including debris which can’t be recycled or reused are taken to land filling purposes or levelling the low lying areas or as base layer filling for road construction. The site for landfill mostly selected from abandoned areas or inactive mines or quarries etc. Also there are specific guidelines to be followed for debris disposal.
The landfill should be done properly by considering the natural resources such as soil, groundwater, vegetation etc. at the disposal area. Proper drainage facilities should be arranged for storm water flow out. The debris should be free from the presence of hazardous waste or lead presence otherwise it will be harmful to the environment.
Elements of Construction Waste Management
In order to maintain a proper waste management system, the following steps are recommended,
Even before the beginning of the construction, there should be a strategic approach to waste management. The waste generation primarily depends on the building materials used. So always ensure the right amount of materials are used for construction.
Always keep information on the waste generation in construction sites and compare it with previous days. In that way it is easy to make statistics of waste production and able to identify from which area and what materials going discarded more.. This process contains two methods, Waste analysis and Waste assessment.
Waste classification and disposal
The waste materials should be classified according to its characteristics into reusable, recyclable, unwanted and hazardous categories.
Waste handling requirements
Inorder to get an efficient waste management in construction site and maximum recovery of materials, a good participation of crew members from the site is important. Organize a special team for waste management and collection is helps to reduce wastage of materials and they needed to be well trained in handling methods of waste, its classification and disposal.
These activities includes time base waste collection and onsite waste recycling system, training of labours about waste management and waste reduction, better coordination in waste collection etc.
While classifying the waste materials into reusable and recycling categorizes, check which all materials are conical for reuse and recycle purposes. The revenue from the materials which can be reusable and recyclable helps to save money on waste disposal.
Challenges in C & D Waste management
As per the available statistics the global construction and demolition waste hits 2.2 billion tonnes by the year of 2025. That means the current waste management system needs to be improved. Also people are more often to go behind virgin building materials other than recycled products. This is because the price difference between recycled building materials and virgin materials are comparatively less. Sometimes the quality of recycled products does not meet upto the level and this is due to mix-up with other materials.
Land levy is increasing day by day. In developed countries it ranges in between $84-$140 per tonnes. Levy rates has soared 200% while we go through the rate statistics of the last decade and it’s still rising.
Concluding notes on Construction & Demolition Waste Management
Considering the Indian scenario the construction industry is the second largest economy which holds up around 11% total GDP. But the construction industry faces some issues like poor productivity and management, the waste production is very high and steadily growing. An average of 15%-30% of total landfill comes from construction and demolition waste or debris in many countries. That means the reuse and recycle principle is not effectively applying in many construction sites.
In India 70% of the construction industry is not aware of waste management and waste recycling. All these data’s pointing to the importance of waste management in the construction industry. At this present age of advanced technologies regulatory bodies must strictly implement procedure to be followed for waste management on every construction site. This can considerably reduce the waste production.