Waste to resources

Written by fe Bureau | Updated: Oct 29 2014, 07:27am hrs
Indias construction sector is forecast to grow at 7-8% each year over the next decade with a new government in place at the Centre, says a recent PwC report. According to PwC, the total construction market in India for FY14 was $157 billion, of which the share infrastructure was 49%, housing & real estate 42% and industrial projects 9%.

The growth of the sector is expected to generate piles of construction & demolition (C&D) waste, something that runs counter to the spirit of Swachh Bharat Abhiyan. It is seldom appreciated that C&D waste can be turned into a resource, for reuse in its original form or for recycling or energy recovery. If ground and cleaned, these materials can be re-used in concrete. Despite this, most C&D waste ends up in landfills and form a significant portion of total solid waste production. It is common to see huge piles of such waste stacked on roads, adding to traffic congestion and disruption.

According to recent Teri report, it is best to sort and store C&D wastes at the source. The waste can be first segregated into road work materials, structural building materials, salvaged building parts and site clearance waste. These can then be further segregated to facilitate reuse/recycling of materials like wood, glass, cabling, plastic, plaster board and so on, says the report titled, Waste to Resources: A Waste Management Handbook.

Recycled materials from demolished concrete or masonry can be profitably used in different ways within the building industry. Concrete materials may be either reused as filler at the same site after completion of work, in road construction or in stone, gravel and sand mines, land fill construction, structural fill in low lying areas to assist in future development, in garden and landscaping.

Concrete and masonry constitute more than 50% of waste generated. It can be reused in block/ slab form. Recycling of this waste by converting it to aggregate offer the dual benefit of saving landfill space and reduction in extraction of natural raw material for new construction.

Recycled aggregate can be used as general bulk fill, sub-base material in road construction, canal lining, playground, fills in drainage projects and for making new concrete to less extent.

Bricks and masonry arise as waste during demolition. These are generally mixed with cement, mortar or lime. It is used in the construction of road base and drayage layer, and mechanical soil stabilisers. Tile materials are also often mixed with brick in final recycled product.

Metal waste is generated during demolition in the form of pipes, light sheet material used in ventilation system, wires and sanitary fittings and as reinforcement in the concrete. Metals are recovered and recycled by remelting.

Wood recovered in good condition from beams, window frames, doors, partitions and other fittings can be reused. Wood wastes have a high market value for special reuses (furniture, cabinets and floorings). Lower quality waste wood can be recycled/burned for energy recovery. Scrap wood is shredded in-site/in a centralised plant. Wood chips can be used as fuel. Also, it is used in the production of various press boards and fiber boards and used for animal bedding.

Bituminous material arises from road construction, breaking and digging of roads for services and utilities. Recycling of bituminous material can be done by hot or cold mixing techniques either at location or at a central asphalt mixing plant it offers benefits like saving in use of asphalt, saving of energy, reduction in aggregate requirement, etc. Other miscellanies materials that arise as waste include glass, plastic, paper, etc., can be recovered and reused.

In the industrialised countries, special landfills are sometimes created for inert waste, which are normally located in abandoned mines and quarries.