IIT researchers develop bio-bricks using agricultural waste products

New Delhi: Researchers at the Indian Institute of Technology have developed "bio-bricks" from agricultural waste products for use in construction.

The invention by the team at IIT Hyderabad in association with KIIT School of Architecture, Bhubhaneshwar, is aimed at serving the dual purpose of waste management and development of eco-friendly and sustainable building material.

Priyabrata Rautray, a PhD scholar at IIT and Avik Roy, Assistant Professor, KIIT School of Architecture, received a Special Recognition Trophy for sustainable housing at Rural Innovators Start-Up Conclave 2019 organised recently by the National Institute of Rural Development and Panchayati Raj (NIRDPR), Hyderabad. "22 per cent of India's total annual CO2 emissions is by the construction sector.

Clay bricks, for example, not only use fertile top soil, but their manufacturing process also emits significant amounts of carbon dioxide into the atmosphere. "Repurposing of agricultural waste is particularly important in India. More than 500 million tons of agricultural waste is produced in the country every year. While some of this is reused as fodder, 84 to 141 million-tons are burnt, which results in severe air pollution," Rautray said.

The IIT scholar explained that the process of making bio-bricks starts with careful selection of dry agro-waste like paddy straws, wheat straws, sugarcane bagasse and cotton plant. "The team decided to use dry sugarcane bagasse for the first sample. The bagasse is first chopped to the desired size. A lime-based slurry is prepared, and the chopped agro-waste is added to the slurry and mixed thoroughly by hand or mechanical mixer to create a homogenous mixture. "This mixture is poured into moulds and rammed with a wooden block to make a compact brick.

These moulds are left to dry for a day or two, after which sides of moulds are removed, and the brick is allowed to dry for fifteen to twenty days. It takes approximately a month's time for these bio-bricks to attain its working strength by air drying," he said. Elaborating on the research, Roy said, "bio-bricks are not only more sustainable than clay bricks, but are also carbon sinks because they fix more carbon dioxide than they produce during their life cycle".

The research team used 900 grams of sugarcane bagasse to make a single block. "Burning this amount of the waste bagasse instead of repurposing it, releases 639 grams of carbon dioxide. Not only is this release prevented in the making of bio-bricks, but the lime in each brick also absorbs 322.2 grams carbon dioxide from the air during curing, which makes it a carbon-negative or environmentally sustainable.

"Although these bio-bricks are not as strong as burnt clay bricks and cannot be used directly to build load-bearing structures, they can be used in low-cost housing with combination of wooden or metal structural framework. Besides, these bricks provide good insulation to heat and sound and help in maintaining humidity of buildings, making these houses suitable for hot-humid climate like India," he said.