Dr Krishna Murari Soni, Former Addl. Director General, CPWD, New Delhi.
Circular economy is a model of production and use through sharing, reusing, repairing, and recycling existing materials and products as far as possible. It is based on the principles of avoiding waste, use of generated waste, and recycling waste for further use as a resource. Circular economy helps in economic development, employment generation, social welfare, sustainable development, land development, energy conservation, and in slowing down the climate change. Since infrastructure development consumes more than 70% of the materials obtained either from nature or industry, the building industry has to contribute towards circular economy for sustainable development.
In India, large infrastructure development was taken up in all the sectors after the Independence, particularly buildings and roads. Most of these structures have outlived their lives and are to be demolished. Some have already been demolished and the demolished material dumped in the landfills. On one hand, such landfill sites are not now fit for construction of new structures and on other side the useful Construction and Demolition (C&D) waste has gone to waste – which is against the principle of circular economy.
Considering the importance of circular economy, the Ministry of Environment, Forests and Climate Change, Government of India has notified “The Construction and Demolition Waste Management Rules, 2016” for management of C&D waste in which, the responsibility of waste management has been given to all C&D waste generators, be individuals, organisations, authorities or the state governments.
The Urban Local Bodies are required to issue detailed directions regarding proper management of C&D waste within their jurisdiction. These include the following:
- seeking detailed plan or undertaking from waste generators
- chalking out stages, methodology and equipment for C&D waste management
- seeking assistance from concerned authorities for safe disposal of contaminated C&D waste
- making arrangement for collection and removal of C&D waste at regular intervals
- transportation of C&D waste for processing and disposal
- incentives to generators for salvaging, processing and recycling
- sanctioning the waste management plan of the generators within a specified period
- keeping track of generation of C&D waste and establishing a data base
- devising appropriate measures for management of C&D waste including processing facility and for using the recycled products
- creating a sustained system of information, education and communication related to C&D waste with expert institutions and civil societies
- making provisions for giving incentives for use of recycled products in construction activities.
Construction and Demolition Waste Management
The C&D waste management plan can be represented by a pyramid having prevention, minimisation, deconstruction, reuse, recycle and disposal in hierarchy as shown in Fig. 1. Prevention or avoidance is the most favoured option while disposal is the least. Prevention and Reuse save materials, energy, water, natural resources and human efforts. Prevention can be achieved through strict quality control in construction and renovation works. Reuse in construction is adopted when “Deconstruction” is adopted. Minimisation can be achieved through better planning, use of green and advanced practices and strict quality control during construction and renovation. Deconstruction has to be adopted over demolition for the benefits of circular economy.
“Deconstruction” is defined in C&D waste management rules as a planned selective demolition in which salvage, reuse and recycling of the demolished structure is maximized while “Demolition” is described as breaking down or tearing down buildings and other structures either manually or using mechanical force (by various equipment) or by implosion using explosives. Therefore, in demolition all the building materials get converted into C&D waste while in deconstruction, materials to a great extent can be salvaged for reuse. Also, deconstruction and demolition techniques both can be adopted simultaneously which is common at the site when the structure is to be dismantled. In such a case, deconstruction technique precedes to the demolition and the materials which cannot be removed for reuse becomes C&D waste and needs to be recycled. The C&D waste which is not recyclable or residue after recycling is to be disposed.
Recycling of C&D Waste
Recycling of C&D waste is now established technique, and equipment, technology, knowhow and government rules, everything is available in the country. Now, the will, change of mindset, incentives and change of specifications and codes for the use of C&D waste is required. Even though, “The C&D Waste Management Rules” have been notified by the government in 2016, setting up of the recycling plants and recycling of C&D waste have not been achieved as envisaged in the Rules. Therefore, either the Rules are to be made mandatory or use of C&D waste recycled materials made mandatory through codes and specifications for their timely implementation.Responsibility of C&D Waste Generators and Local Authority
As per “The Construction and Demolition Waste Management Rules, 2016”, C&D waste generator is a person or association of persons or institution, residential or commercial establishment undertaking construction or demolition of any civil structure generating C&D waste. Every waste generator is prima-facie responsible for collection, segregation of concrete, soil and others and storage of C&D waste as per the directions of local authority.The waste generator has to ensure that other waste such as solid waste does not get mixed with C&D waste and is kept within the premise or get deposited at collection centre for transporting to processing facilities. Waste generators who generate more than 20 tons or more in one day or 300 tons per project in a month have to segregate the waste into four streams i.e. concrete, soil, steel - wood and plastics, and, bricks and mortar, submit waste management plan and get appropriate approvals from the local authority before starting construction, demolition or remodelling work. Such waste generators have also to keep the concerned authorities informed regarding the relevant activities from the planning stage to the implementation stage of the projects, pay for the processing and disposal of C&D waste generated by them, apart from the payment for storage, collection and transportation as per the rates fixed by the concerned local authority or State Government.
As per the Rules, local authorities have been given responsibility to make provision for giving incentives for use of recycled materials in the construction. Therefore, all state governments and local bodies are certainly going to devise their C&D waste management plans in near future even though little progress appears to have been made during last seven years.
Recycled C&D Waste Materials
Major constituents of Indian C&D waste are concrete, soil, bricks, wood, asphalt, and metal. Concrete, brick masonry, and sand/gravel constitute around 90% of total C&D waste (Technology Information, Forecasting and Assessment Council’s, 2001) while bricks and masonry, soil/sand and gravels constitute about 60%, however the constituents may vary from site to site and according to type of structure. In case, C&D waste consists of only cement concrete, recycled aggregates are sand (Fig. 2) and coarse aggregates called Recycled Concrete Aggregates (RCA) (Fig. 3) and if includes brick bats also, recycled aggregates have a mix of natural and brick aggregates and are called Recycled Aggregates (RA) (Fig. 4). Apart from this, soil paste known as filter press material (Fig. 5) is received as a residue after screening of sand, aggregates and other bulky materials is complete.
Process of recycling C&D waste includes feeding, sorting/pre-screening, crushing/scrubbing, containment/metal removal, sand washing, aggregate sizing and sedimentation of sludge and conversion into filter press material. Main recycled materials are sand and coarse aggregates. Metals, wood and asphalt etc are removed before recycling.
Assessment of C&D Waste and Recycling Plants
As a thumb rule, generation of 40-60 kg per sqm C&D waste is considered in construction & renovation and 300-500 kg per sqm in demolition, though it appears that construction may not generate such quantity. Construction activities may generate hardly 8-10 kg per sqm C&D waste if 40-60 kg per sqm is considered in renovation. Even with this assumption, country is going to generate large amount of C&D waste hence a proper management plan has become a necessity in all the municipal corporations.The annual generation of C&D waste in India was estimated to be around 12-15 million tonnes (MT) during 2000, around 25-30MT during 2014 and more than 100MT during 2018. It is estimated that Delhi generates about 4600 tonnes C&D waste, Mumbai and Chennai about 2500 tonne each, Kolkata 1600 tonne and Bengaluru 875 tonnes per day. Even cities like Ahmedabad generates @ 700tpd, Jaipur @ 200 tpd and Patna @ 250 tpd.
In case C&D waste plants of 500 tpd are installed, more than 500 plants will be required in the country for recycling 100 million tonnes. Even for 30 MT, more than 150 plants would be required. As such, there is large scope for installation of C&D waste recycling plants however plants are installed or are under installation process in few cities only such as Delhi, Mumbai, Hyderabad, Noida, Ghaziabad, Ahmedabad, Chandigarh, Thane, Indore, Gurugram, Bengaluru, Tirupati, Vijayawada, Surat.
Three types of C&D waste recycling plants are available as mobile, semi-mobile and stationary plants. Mobile plants can be transported to the demolition site itself and are suited to process only non-contaminated concrete or masonry waste and are dry processing type usually mounted on trucks. They may produce dust at the site hence have to be installed only at the sites away from habitable areas. In semi-mobile plants, removal of contaminants is carried out manually and the end product is also screened. End product quality is better than that of a mobile unit but these plants are not capable to process mixed demolition waste containing materials like metal, wood, plastic, etc. Stationary plants are equipped for carrying out crushing, screening, metal removing as well as washing.
Opportunities and Challenges for use of C&D Waste
Recycled sand and RCA have large opportunities and can be used in various applications even though allowed upto 25% in plain CC, 100% in lean concrete, and 20% in RCC of upto the grade M25 (Table 1). Various products are being manufactured from RCA as shown in Fig. 6 (IL&FS Environment Plant at Burari Plant, Delhi) and also being used in RMC. But Recycled Aggregates (RA) has very limited use i.e. only in lean concrete as per IS: 383 probably due to variable properties of brick masonry, mortar and proportion of concrete aggregates of C&D waste. Therefore, finding use of RA appears to be a challenge before the researchers though it may prove to be an opportunity also if its use is standardised for major applications like road works and included in IRC codes which will result in saving of natural materials like aggregates and soil. Since quantity of RA is significant, operation of recycling plants may not be financially viable until and unless RA is permitted in various useful applications to avoid recycling sites being converted into dumping yards.
Governments and local bodies are also encouraging use of recycled products. CPWD has already allowed use of recycled aggregates as per BIS code. Delhi Government has also issued an advisory for use of recycled products. Other governments are on same path and as such C&D waste is going to be a resource for infrastructure development. This will provide a good opportunity to enter into the business of recycling C&D waste.
Another challenge in use of recycled C&D waste materials is acceptability and awareness. Few engineers feel that recycled sand and aggregates from C&D waste maybe of inferior quality. IS code also allows recycled aggregates for limited use thus not providing confidence to the engineers and architects for the durability. Hence, use of RCA and RA needs to be widened by BIS and to be allowed by IRC.
Sand and RCA are being used in manufacturing tiles, kerb stones, concrete blocks, precast RCC/CC components, however RA is not used in general for such products. Uses of RA other than in lean concrete and filter press material are to be found out as early as possible. IL&FS Environment in their recycling plant at Burari, Delhi has used RA in manufacturing concrete blocks (Fig. 7) after considerable experimentation to obtain desired strength, still quality of such blocks cannot be confidently assured. Probably, RA may suit to applications like for sub base and base course in road works, under floors, footpaths, plinth protections, part replacement of clay in burnt clay bricks etc. though a research is to be done and items included in Schedule of Rates and Specifications. CPWD (Makkar, 2018) has reported use of about 17.50 lakh cement concrete blocks manufactured from RA in Supreme Court additional office complex, New Delhi in external walls, toilet walls and lift well walls of RCC framed structure, and included block masonry from recycled C&D waste in DSR.
Similarly, use of filter press material needs to be found out. Possible use may be in filling, horticulture operations, and in making bricks in case it does not include non permissible contaminants.
Concluding Remarks
- Due to environmental considerations and to harness benefits of circular economy, recycling of C&D waste has become a necessity. There is a large scope of recycling plants considering the quantum of C&D waste being generated in the country.
- Change of mindset, awareness, the will and capacity building for use of C&D recycled waste among stakeholders is essential for acceptability of recycled products.
- Recycled products are to be researched for wide use in structural members of buildings and roads.
- BIS, IRC, CPWD, PWDs and local bodies are to encourage use of recycled products by way of including them in their codes, Schedule of Rates and Specifications to make C&D waste a resource material.
References
Construction and Demolition Waste Management Rules, 2016, Ministry of Environment, Forest and Climate Change.Guidelines on Environmental Management of Construction and Demolition (C & D) wastes, 2017, Central Pollution Control Board, New Delhi.
Soni, K M (2021), Recycled C&D Waste Materials, NBM&CW, Vol. 26(08), 70-72.
Makkar, B B (2018). Supreme Court Additional Office Complex, N. Delhi – Innovative technologies Intervention. Emerging & Innovative Technologies for Sustainable Development, CPWD, New Delhi.
Soni, K M (2014), Avoidance of Waste Generation for Construction and Demolition Waste Management. Preliminary publications, Indian Buildings Congress, Vol. XXI (2), 14-19.
Strategy on Resource Efficiency in Construction and Demolition Sector, MoHUA and Niti Aayog, January, 2019.
https://en.wikipedia.org/wiki/Waste_hierarchy
http://www.ilfsenv.com/Compost-Products.html
