Researchers from Indian Institute of Technology Hyderabad and KIIT School of Architecture, Bhubaneshwar, have developed bio-bricks for construction from agricultural waste products. Their development serves the dual purposes of waste management and development of eco-friendly, sustainable building materials.

This research was undertaken by Ar. Priyabrata Rautray, PhD scholar, Design Department, IIT Hyderabad and Ar. Avik Roy, Assistant Professor, KIIT School of Architecture, Bhubaneshwar. The results of this research work, which was guided by Prof. Deepak John Mathew, Head, Design Department, IIT Hyderabad and Dr Boris Eisenbart from Swinburne University of Technology, Australia, have been presented at the International Conference on Engineering Design (ICED-2019) at TU Delft, Netherlands.

The team’s bio-brick received a Special Recognition Trophy for sustainable housing at Rural Innovators Start-Up Conclave 2019 organised recently by National Institute of Rural Development and Panchayati Raj (NIRDPR), Hyderabad.

Speaking about the need for ‘bio-bricks,’ Ar. Priyabrata Rautray, PhD Scholar, Design Department, IIT Hyderabad, said, “22 per cent of India’s total annual CO2 emissions is by the construction sector. Clay bricks, for example, not only use up fertile topsoil, but their manufacturing process also emits significant amounts of carbon dioxide into the atmosphere. Recognising this problem, the Building Materials and Technology Promotion Council (BMTPC) was set up in the 1990’s by the Central Government to develop eco-friendly and energy-efficient building materials, providing impetus into repurposing agricultural and industrial waste items into construction materials.”

Repurposing of agricultural wastes is particularly important in India. More than 500 million tons of agricultural waste are 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. Ar. Priyabrata Rautray and Ar. Avik Roy have found a new way to repurpose agricultural waste materials. They use it to manufacture bricks, a commonly used construction item.

The process of making bio-bricks starts with careful selection of the 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 the sides of the 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.

Elaborating on this research, Ar. Avik Roy, Assistant Professor, KIIT School of Architecture, Bhubaneshwar, 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 lifecycle.”

For example, 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 the buildings, making these houses suitable for hot-humid climate like India.

“Other than as bio-bricks, this material can be used as panel boards or insulation boards and designers we could explore such applications for this sustainable material,” added Ar. Rautray. The team continues to study such designs and also seeks ways in which the load-bearing capacity of the bricks can be improved.

The ‘Bio-Bricks’ developed from Agricultural Waste Products by IIT Hyderabad and KIIT Bhubaneshwar Researchers