Building & Construction Waste
In the present era of the circular economy, we need strategies our-self to reduce waste are particularly important in the built environment. Such waste is accounting for a fifth of global emissions. Circle Economy calculates that nearly half of all materials going into the economy — 42.4 billion tonnes a year — are used in the construction and maintenance of houses, offices, roads and infrastructure.
The opportunity requires global coordination, as countries will need to adopt different strategies. In emerging economies, where high population growth and rapid urbanization are driving a massive building boom, the challenge is to adopt building practices which minimize the use of raw materials and consequent emissions.
The construction and demolition (C&D) waste which can be recycled include metals, paper, glass, plastic, wood, concrete and other construction materials such as bricks, rubble, plasterboard and asphalt. In the present scenario, protection of the environment is a key concern of every sector including construction and building recycling sector. On the construction & demolition sites, key environmental considerations include the reduction of waste and the re-use and recycling of waste materials.
Recycling of waste material on-site can offer real benefits, not only through better planning and compliance with regulations but also savings in waste disposal charges. There are also a number of waste and recycling-related laws which require organization’s to account for their waste, and government initiatives to encourage recycling. This leads to savings on material costs as well as waste disposal charges.
India’s construction industry is the largest consumer of the basic material of both the natural ones (like stone, sand, clay, lime) and manufactured and synthetic ones. During the last 50 years or so, there has been some unplanned, unchecked and haphazard exploitation of mineral resources like limestone, clay, iron ore, bauxite, coal etc. Further, the growth in industries is continuously throwing huge quantities of wastes and byproducts such as fly-ash from power generation & blast furnace slag from the iron industry, red mud from the aluminium industry etc.
Also, a huge amount of Municipal waste is generated every day in each Indian city and World over. For example, Delhi alone generates about 650 tons of garbage every day. By 2020 its amount may reach 1,800 tons. Generally, the disposal areas are an outside city which is miles apart. Such an amount of waste disposal is a Herculean task and needs space for dumping and fuel for transportation.
As waste continues to accumulate and availability and capacity of landfill spaces diminish, so it is necessary to recycle and use it as construction material especially for Sustainable Development. Infrastructure construction uses a tremendous amount of material which can also be recycled materials. Delhi government has decided to mandate recycled products from C&D waste in prospective contracts for building works and road works to be taken up by the government and its agencies.
Following the decree, all Delhi government authorities are required to incorporate a clause in their tenders: It mandates the use of a minimum of two per cent recycled products from construction waste in all future contracts for building works and ten per cent recycled products for roadworks. Five per cent use of such products is expected for non-structural applications during examining and approving building plans.
Aiming at the Delhi government, these recommendations apply to whole Indian C&D waste management policy as well. The demand for this material will rise. For two-thirds of the buildings that will stand in India in 2030 are yet to be constructed. But the environmental cost will only compound with the anticipated construction boom unless immediate steps are taken to recycle and reuse construction waste as a resource.
The Municipal Corporation of Delhi East has built a new C&D waste recycling plant to cater to the waste being generated in its area. However, the products manufactured by the recycling plant have difficulties in finding any takers due to lack of information and the absence of a C&D waste policy or standards. This is not only a problem of Delhi but a structural problem of India`s waste management.
Therefore, Material Recycling Association of India (MRAI) working with the Government Policy Makers to include such C&D Waste key aspects in the National Material Recycling Policy to cover the all aspects which will help to minimise pollution and landfills. Besides, the megacity`s government has acknowledged that processing of construction and demolition waste has great potential to save urban space, will reduce negative environmental impacts, and it can conserve natural resources and will address the shortage of building materials.
Generally, over 30% of the building materials purchased for your project can go to waste, but you can save much of this by reducing waste production, and re-using and recycling the waste that is produced.
Better materials and waste control policies, like on-site waste segregation and reduced Many waste materials, can be recycled either through the manufacturer or by recycling companies, avoiding the need to send them to landfill altogether and so reducing costs. We can also re-use materials on-site, which achieves a further cost saving by reducing the number of new materials which are required. Waste that is not segregated may be impossible to recycle and may, therefore, have to be sent to landfill.
It is necessary that all construction sites are required to handle and dispose of waste safely and responsibly. Therefore, procedures for handling waste should be a part of National Material Recycling Policy. However, it is important that all workers on-site understand what they are required to do with their waste, to ensure that your site complies with the law.
Many companies now have formal policies on waste management and recycling, often as part of broader corporate aims such as sustainable construction. Even if most of the companies do not have such a policy, the client or main contractor on a site may require that to work with as per the recycling policy to minimize landfills and to keep the environmental balance.
Ms Anumita Roychowdhury, head of the Center for Science and Environment’s Sustainable Urbanization team, commented: “This is an important move forward as construction and demolition of buildings cause enormous waste – about half of all materials used – that degrades the land and environment.”
Demolition Waste (Malwa)
Waste Generation: Construction industry during rehabilitation, repairs and modernizing the buildings produce huge waste called demolition waste or MALWA. A typical waste dump is shown in figure 4. A further huge amount of Municipal solid waste is generated every day in each Indian city or town. It is estimated that per capita waste generation in major Indian cities generally ranges from 0.4 to 0.8 Kg per day per person.
The central pollution Control Board estimates the current quantum of municipal solid waste generation in India to the tune of 50 million tons per annum. Out of total waste generation, the construction industry accounts for over 15 million tons or about 50% of total solid waste depending upon location and duration. The waste contributes to greenhouse gas emissions which should be reduced by its recycling. Thus the greenhouse gases and methane gas emissions etc can be controlled.
Waste Management: When analyzed, a typical waste product distribution in any solid waste dump is shown in the above picture. Waste management is on the principle of 3 R’s; i.e. Reduce, Recycle and Recover/Reuse or otherwise dispose of it. The waste management involves different methods for its processing as given below:
- Collection and Disposal for landfill area and/or incineration.
- Recycling – physical and biological processing
- Energy recovery
Reduce – where possible stop waste coming on-site in the first place. This can be achieved by ordering only quantities which are required and speaking to manufacturers to order size-specific items which do not require cutting to size.
Re-use – the next option should always be to consider whether the materials can be re-used, either on-site or by someone else. Items such as timber, tiles and bricks are often easily re-used. Packaging items such as pallets and crates may also be collected by the supplier for re-use elsewhere.
Recycle – this option is for all materials which can’t be reduced or re-used. It involves processing the waste material, for example crushing concrete to make aggregate or melting metal or glass to form new products. Some recycling can be carried out on-site, but often the waste has to be sent to an offsite recycling company for processing. Segregation of wastes to prevent contamination is important for recycling and will ensure that skips aren’t rejected by the waste contractor.
Recycled Concrete Material (RCM), also known as crushed concrete is similar to demolition waste. Primary sources of RCM are the demolition of existing concrete pavement, building slabs & foundations, bridge structures, curb and gutter and from commercial/private facilities etc. It is a reclaimed material. This material is crushed by mechanical means into manageable fragments and stockpiled.
RCM may include small percentages of finer particles / sub-base soil or debris. Such materials have to be screened out and used as sand or fill material. The resulting material is normally in the form of Coarse Aggregate. Comprised of highly angular conglomerates of crushed quality aggregate and hardened the cement, RCM is rougher and more absorbent than its virgin constituents. The difference between the various grades of concrete mixes of demolition concrete results in varying qualities of aggregate and sizes.
Advantages of Using both Demolition Waste (MALWA & RCM):
By making use of locally available demolition waste and concrete material aggregates, there would be sufficient reduction in aggregate requirement at a construction site.
Processing of waste will make the system Sustainable. It will also save energy & resource of materials which can be usefully utilized at a later time.