Every day, Bengaluru generates nearly 3,000 tonnes of construction and demolition waste and debris – roughly equivalent to 250 truckloads of material. Most of this waste, which totals to about 10 lakh tonnes every year, is dumped in undesignated landfills.

Meanwhile, more buildings are constructed in the city every day, with fresh construction material being obtained by crushing hillocks in the area.

The construction industry is one of the biggest contributors to carbon emissions: it accounts for 37% of global emissions according to a recent United Nations report. In addition, crushing activities are noisy and hurt the vegetation in the region. The dust this generates could cause lung problems.

It is, thus, critical that construction waste is reused more efficiently. But because this waste does not smell or contaminate the groundwater as obviously as household waste, urban local bodies ignore this vital need.

Construction debris. Image provided by Indian Institute for Human Settlements

Bengaluru, as a hub for technology and other industries and an increasing migrant population, has a fast-growing construction sector that builds a vast number of apartments, offices and tech parks, educational institutions and public infrastructure.

The peripheral zones in Bengaluru (Bengaluru North, Bengaluru west, Yelahanka, Mahadevapura) generate more construction waste since they have more building activity.

While the construction of private buildings is a key contributor of waste, a major source is also from the construction of infrastructure such as roads, metro rail, airport infrastructure and flyovers.

In 2014-’15, the Bruhat Bengaluru Mahanagara Palike floated a plan to set up processing and value recovery systems – recovering material which can be sold or used to make paver bricks – for construction and demolition waste, with a capacity close to 2,000 tonnes. While detailed project reports were prepared and tenders were invited to set up these plants, there has been no update about the plans.

Challenges of construction waste

Construction and demolition waste generated by mainstream projects comprises gravel, M-Sand (artificial sand produced from crushing hard stones into small, finely graded particles), cement, brick masonry and steel.

This construction and demolition waste has to be segregated to recover useful construction material, such as the gravel, M-sand and steel.

Ideally, urban local bodies need to procure this waste and set up processing plants to recover the usable material. Local bodies could also purchase products made by the recycling facilities, such as construction masonry blocks and paver blocks. These could be used to build public infrastructure such as footpaths and cycle paths.

Paver blocks at a construction and debris plant in Indore, in this photograph from 2019. Credit: Credit: SV Pushkara

Collection, disposal

For now, construction waste is disposed of in low-lying areas, landfills, quarries and other available places. Even bulk construction waste generators, such as the Bengaluru Development Authority, Bruhat Bengaluru Mahanagara Palike or the railway authorities, do not have a mechanism to process their waste.

Debris is usually removed and transported away from construction sites at night to avoid traffic. There is no system for tracking transport. Tracking would mean a fee has to be paid for transporting this waste, which could be challenging to implement.

Expenses, processing

The waste differs according to the type of construction so debris from sites cannot be handled in a uniform way. For example, construction waste from a Metro project cannot be processed in the same manner as that from an apartment building.

This is because the nature of construction waste generated in metro works consists of more soil, stones and other such material because of underground excavation whereas other demolition works comprise concrete, wet mix, steel, sanitaryware and others.

This is a challenge that will need proper mechanisms in place for each type of construction.

The process of value recovery from construction waste is more complex than simply obtaining fresh material. When the waste is received at a site, it needs to be inspected to decide the processing required to make it usable. This can be a lengthy process with several rounds of sieving and segregation.

Materials such as gravel and aggregates are cheaper per tonne when produced fresh compared to recovering debris. At present, fresh material such as gravel is available for Rs 700 per tonne, including transportation, whereas gravel recovered from construction waste costs Rs 800 per tonne.*

This is a major reason why recycled material is not chosen as keeping production costs lower is a priority in large-scale construction.

A view of the Bengaluru skyline. Credit: Kushagra140, CC BY-SA 4.0 via Wikimedia Commons

The way ahead

Cities such as Delhi, Ahmedabad and Indore have construction waste processing plants – Delhi with a capacity of 4,000 tonnes per day and Indore and Hyderabad at 300 tonnes a day. Municipal corporations use the material for paver blocks, kerb stones and the like.

In these cities, stone quarries are located far away from the city. Therefore, using recycled material makes financial sense because the extra cost of recycled material is offset by cheaper transport.

But in Bengaluru, the abundant availability of construction raw material has made it financially unviable to spend more for recycled material.

Though sourcing fresh construction material is cheaper and easier than recycling, Bengaluru cannot afford to exhaust all the natural resources around the city and needs to reuse construction debris to lower the effect on the environment. This requires the state to step in and offset costs.

The Swachh Bharat Mission 2.0 guidelines released on October 26, assure subsidies for setting up plants to process municipal solid waste and construction waste.

A commitment to the use of recycled material is also required from large consumers such the railways and Metro rail departments. Taking such steps could help protect lake beds from being filled with waste and reduce crushing of hillocks.

*All figures are the authors’ estimates based on previous work.

Pushkara SV is a practitioner at the Indian Institute for Human Settlements, Bengaluru, with experience of working at over 60 Urban Local Bodies across the country. His work has focused on improving the efficiency of waste collection and processing.

Avinash Madhwaraj is a practitioner at IIHS and has about 15 years of experience in engineering, construction management, operations and project management