Construction of buildings and the manner of living in them contribute greatly to carbon dioxide emissions. The United Nations Environment Programme says that ‘buildings’ account for nearly 40 per cent of all energy-related carbon dioxide emissions.
Even as the world has been trying to come up with new, climate-friendly building materials (from hollow clay bricks to bamboo), there is a growing realisation that, aside from new materials, the utilisation of materials on hand could be a big help. These materials range from agri-waste to ‘construction and demolition’ (C&D) waste.
Estimates of C&D waste vary, but it is safe to assume that the country produces a billion tonnes of them. A lot of useful material can be mined from them — steel rods, sand, pebbles.
Needless to say, India also produces a lot of agricultural waste, a good portion of which can go into construction materials — such as coconut fibre, fly ash from bagasse, and rice husk-fired cogeneration plants.
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At IIT Madras’ Centre for Technologies for Low Carbon and Lean Construction, research is underway to use C&D and agri wastes in sustainable concrete structures.
The centre is also setting up a test-bed to evaluate the use of agricultural, industrial, construction and demolition waste in building durable and sustainable concrete structures.
Prof Manu Santhanam, who heads the Technologies for Low Carbon and Lean Construction (TLC2) project, says the test bed will direct practices, policies, and standards for utilisation of waste material from various other industries and reduction of waste in the construction industry. “We are on the verge of developing India's first-ever test-bed facility for cement and aggregates production and characterisation. This could be used by the industry and government or non-governmental organisations,” he says.
In particular, the project aims to leverage technologies to reduce the extent of material and process waste in concrete construction projects. “The primary vision of TLC2 is to become the primary destination in India for everyone interested in developing and implementing ideas on low-carbon and lean construction technologies,” Santhanam told Quantum.
Santhanam and his team, Prof Ashwin Mahalingam and Prof Surender Singh of the Department of Civil Engineering, believe it is possible to drastically reduce carbon dioxide emissions in the construction industry, there being many low-hanging fruits. For instance, you can coordinate operations to ensure that construction equipment such as cranes and trucks, which are typically diesel-guzzling,do not idle. There are software tools, such as ‘Last Planner System’, to help systemise workflow, rather than leave it to the acumen of project managers.
There is also plenty of scope for technological intervention in waste management and use. For instance, the centre is working on using computer vision and robotics for segregating recyclable material from waste, and computer vision for monitoring the quality of 3D-printed concrete. Surender Singh is working on the use of solar energy for recycling concrete, use of coconut coir for concrete pavements (mainly to prevent cracks), the use of recycled asphalt pavements for generating aggregates for concrete, and the development of clay-based alternative cementitious mortars.
The centre is working on projects that could have significant application in the field, including developing a new ‘framework of high value-added zero-waste recycling of concrete from construction and demolition waste’, in collaboration with Brunel University, London.
Santhanam underscores the importance of policy-push. For example, can the government mandate the use of a certain percentage of C&D in new constructions, as some other countries do? Perhaps also a certain percentage of agri-waste? Policy does help, as seen in the case of manufactured sand (M-sand), as consumption increased after it was mandated.
A Chennai-based start-up, Westart India, engages in the collection of C&D waste (and other wastes, too) to make M-sand. In Chennai alone, it collects about 800 tonnes of C&D waste each day. And that is the way to go.