C&D Waste Management
With the growth of construction, the environmental problems arising due to the construction & demolition (C&D) waste has become a major issue for the urban development bodies. Ankit Gohel finds out more.
The increase in urbanization in India has resulted in the rise of economic activities in the cities and growth of construction sector in India. The metro cities have seen a sharp increase in infrastructure projects like development of expressways, metro rails, commercial and IT hubs, airports, housing societies and many more. But, the cities are far lagging behind in establishing an efficient construction & demolition waste management system.
Most construction waste goes into landfills, increasing the burden on landfill loading and operation. Waste from sources such as solvents or chemically treated wood can result in soil and water pollution. Also, the land required for these comes either from deforestation or the cultivated land. This creates a severe rise in the pollution level of the area.
The Government of India has notified Construction & Demolition Waste Management Rules, 2016 for the first time. The Act streamlines all the waste generators, service providers, state authorities, local bodies, various ministries and pollution control boards to work towards taking effective steps to recycle and reuse the construction and demolition (C&D) materials. Under the new construction and demolition rules, a person generating over 300 tons of construction waste will not only be required to hire an agency for its disposal, but will also have segregate the waste into concrete; soil; steel, wood and plastics; and bricks and mortar; and have to submit a waste management plan.
The Construction & Demolition (C&D) materials consists of Concrete, Wood (from buildings), Asphalt (from roads and roofing shingles), Gypsum (the main component of drywall), Metals, Bricks, Glass, Plastics, Salvaged building components (doors, windows, and plumbing fixtures), Trees, stumps, earth, and rock from clearing sites.
There are generally two sources of generation of construction waste materials, viz. the Bulk generators and the Small generators. The Bulk generators include the repairs of roads, bridges, flyovers, parks, etc. which come under the infrastructure sector. The other source is the small generators which are housing, industrial, and commercial building construction, demolition of unauthorized structures etc. that are considered under the real estate sector.
C&D waste constitutes a major proportion of the total solid waste generated in the urban towns and cities in India. It is estimated that the construction industry alone in India generates about 10-12 million tons of waste annually.
Almost, 55,000 million cubic metre and 750 million cubic metre of aggregate is the projected shortage in raw material available for the housing and road sector, respectively. Recycling of aggregate material from C&D waste will reduce the demand-supply gap in both these sectors. Recycling of C&D waste is widely practiced in countries like UK, USA, France, Denmark, Germany and Japan.
A study reveals that, congested construction sites, sites in heavily built‐up areas with no ability to have an alternate storage or staging location for materials, lack of ownership of waste due to the presence of multiple contractors on the construction site and lack of awareness and education among the construction workforce were regarded as major challenges associated with the implementation of waste minimisation practices in India.
Recycling & Reuse
In general, 90-95% of the total construction material waste can be recycled and the recycling of construction material can reduce the load on landfills which is around 25% of the total waste generated in India. However, little has been done to manage and utilize C&D waste in a scientific manner. Value of waste can be increased by using this for benches, pave bricks, Curb stone thus fetching more commercial value than dumping these in landfills.
Many building components can be recycled. Organic materials such as wood and plant wastes will be recognized as important components of biofuel feedstock in the generation of so-called green power. Metals like steel, copper and brass can be well utilised again in different ways. Asphalt and concrete can be recycled into new asphalt and concrete products.
Reusing and recycling of these waste materials results into reduction of the pollution caused by them. According to a study, reducing the amount of C&D materials disposed of in landfills can create employment and economic activities in recycling industries and provide increased business opportunities within the local community. The onsite reuse of materials can also reduce transportation costs which ultimately cuts overall project building expenses.
Recently Ireland based CDE Global installed its first ever C&D waste recycling plant in India, fully designed, engineered and commissioned for IL&FS for an MCD project in Delhi. The plant has been successfully processing C&D waste into recycled aggregates which can be used for brick making and building roads
The C&D waste recycling plant circuit includes – vibrating grizzly feeder hopper; RotoMax logwasher for heavy-duty aggregate scrubbing; double deck ProGrade wet screen with high pressure jets for rinsing and separating aggregates at two decks; sand wash plant with a combination of a sump, pump, dewatering screen and hydrocyclones for two stage sand cleaning process to remove the unwanted ultrafine particles (mainly clay) from sand; and AquaCycle high rate thickener for water recycling.
Similarly, the Ahmedabad’s construction and demolition plant was set up through a Public Private Partnership (PPP) model between Ahmedabad Municipal Corporation and Amdavad Enviro Projects Pvt Ltd. It has a mammoth treatment capacity of 100 MT per hour and the service includes complete transportation, treatment and recycling of construction and demolition waste of the city of Ahmedabad.
This is a green project as it focuses on harnessing finished product from construction and demolition waste. C&D waste otherwise being dumped into landfills is transformed in usable products. The plant uses minimum amount of water and is a model plant for zero water discharge concept as whole of water is used and make up is only due to product bound water loss or process loss. The administrative building of the plant has also been developed and constructed as per Green Building Concept with energy efficient solar panel for energy harvesting.
How to minimize jobsite waste
Small steps taken during construction towards reducing and reusing waste materials are as significant as the use of modern technology in waste management practices. There are many ways a developer can recycle the construction waste or demolition debris at the jobsite. The construction type of the buildings and the project schedule are the two primary factors in determining what and how salvage, reuse or recycling can be done.
The project schedule should be developed to accommodate salvage, reuse or recycling. As per industry experts, up to 10-20% of a project’s construction waste stream can be cardboard alone. Therefore, a contractor can purchase in bulk to avoid packaging for volume purchases. Also, they can use returnable containers and packing materials while the non-returnable containers and plastic barrels and other materials can be reused on the jobsite.
The use of materials which get spoiled within a short time should be limited. It is also to be ensured that volatile materials and materials that degrade when exposed to heat, cold, or moisture are protected from spoilage and are not wasted. A buy-back contract with the suppliers will also prove efficient and helpful to reduce jobsite waste.
The quality and quantity of materials restored is direct function to the time available for salvage. Before demolition, restore as much usable materials as the schedule will allow. Electrical fixtures, plumbing fixtures, windows, doors, wooden flooring, mechanical equipment, cabinetry, etc. can be salvaged and reused. It is important to identify the valuable materials to optimize the use of resources while developing the C&D Waste Management Plan.
With the help of modern portable equipment, the materials like concrete can be recycled to produce aggregate on the site itself. The rubble can be transported to the recycling plants. Steel and metals are usually recycled everywhere.
The preferences of the demolition contractors and recyclers may vary about whether the building should be gutted prior to demolition, leaving only concrete and reinforcing to be crushed, or demolished intact, and the debris sorted as part of the concrete crushing process.
Consider how the recycled concrete aggregate (RCA) will be used, what RCA products are most useable, and how the rubble should be processed to produce these products. If aggregate materials are required for the project, on-site recycling can provide these materials at a reduced net cost.
The wooden materials that are not treated with an arsenic-based preservative, or painted with lead-based paint or contaminated can be cut into mulch or composted. This can be done even on-site.
Old growth timber is a valuable material and will usually justify the time required for a more delicate removal process. Timbers are generally sold through timber brokers to be cleaned and resold for timber framing, or as feedstock for high quality architectural millwork.
Reducing the amount of C&D materials disposed of in landfills or incinerators can create employment and economic activities in recycling industries and provide increased business opportunities within the local community, especially when deconstruction and selective demolition methods are used. It reduces overall building project expenses through avoided purchase/disposal costs. It also leads to fewer disposal facilities, potentially reducing the associated environmental issues. It offsets the environmental impact associated with the extraction and consumption of virgin resources and production of new materials and conserves landfill space.
Now-a-days, the industrial recycling equipment manufacturers are investing in development of improved machinery which has potential to revolutionize the efficient sorting and diversion of waste. Industrial shredders reduce physical volume and produce particles of consistent dimension, allowing efficient mechanical separation. Industrial air separation technology allows efficient segregation of materials with differing mass characteristics, thus separating small pieces of wood and plastic from metal and aggregate.
The energy prices are going high. Thus, the construction and demolition waste can be recognised as an alternative. With the advancement in technology and proper management techniques along with effective government regulations, there can be improvement in the diversion of wastes from the landfill towards energy generation and recycling of materials.
Landfills located in wet regions, near waterways, and in other environmentally sensitive areas will continue to trend toward closure. Post-closure expenses for management of landfills will continue to increase, with environmental monitoring and greenhouse gas management being significant priorities. Costs for disposal in many areas may continue to increase faster than the cost of energy, creating a de facto demand for increased diversion, recycling, and reuse.
Recycling the construction waste would not only lead to reduced pressure on the natural resources but would also lead to mass employment in the waste sector.
Time to Act Sustainably
The C&D waste generation is expected to increase with the rise in construction activities in India. Effective measures are needed to be taken to minimize and handle the C&D waste as it may threat environment as well as sustainable growth of the country.
Evidently, C&D waste minimization and handling are necessary in view of limited landfill space and increasing quantum of demolition waste otherwise there may be issues related to handling the waste and finding space for landfilling. This will cause an extra burden on solid waste management plans, which are already looking for new ways to fight with the growth in municipal solid waste due to increase in urban population and developments in the country.
It would be desirable to have more accurate and detailed data such as C&D waste generation and the way it is managed in India. 3Rs policy and use of waste minimizing technologies e.g. design for deconstruction and reuse of materials should be adopted to minimize C&D waste. Recycling of C&D waste by converting it to aggregate may offer dual benefit of saving landfill space and reduction in extraction of natural raw material for new construction activities, leading towards sustainable development.