Did you know the common burnt clay brick used in most construction projects is also one of the most energy- and resource-intensive building materials to manufacture?

Brick kilns use a diverse range of energy sources to fire bricks, ranging from coal, firewood and various solid fuels to diesel and natural gas, releasing noxious pollutants and particulate matter into the environment. The typical burnt clay brick has a carbon footprint of about 500gm CO2 – this means the brick manufacturing industry is responsible for millions of tons of carbon emissions each year, adding to the burden of the construction industry, which is one of the biggest polluters in the world today. According to WeForum, cement and brick production could be responsible for 7-8% of global CO2 emissions.

Added to this, the raw material for bricks comes from top soil and clay, depleting precious land resources, which could otherwise be used to grow food.

Keeping in mind the ongoing climate emergency, it has become imperative for stakeholders in the construction industry to seek low carbon building products to replace the existing polluting materials. Innovations in the brick manufacturing sector are exploring the use of low carbon materials sourced from industrial/municipal waste, hemp and agro-waste among others.

Hempcrete Bricks

Hemp bricks by IsoHemp (Image: IsoHemp)

The raw material for hempcrete bricks comes from the hemp plant, which can grow in most soils and climates, reducing the journey from farm to factory, and thereby, the emissions. By absorbing copious amounts of carbon over its lifetime, the hemp plant is an effective carbon sink.

Hemp blocks from IsoHemp are non-load-bearing glued masonry products recommended for creating building envelopes, partition walls and counter partitions. Suitable for both new constructions and renovations, especially in the residential building sector, IsoHemp hemp blocks can efficiently regulate temperature and humidity, and deliver acoustic insulation and fire resistance. The low-energy manufacturing process uses locally sourced 100% natural hemp and limestone. A pallet of IsoHemp hemp blocks stores 100kg of CO2, and a wall built using hemp bricks has a carbon footprint of -72.0 kg/m², making it a very green building material.

Gent Waste Brick

The Gent Waste Brick (Image: Bart van Leuven)

The Gent waste brick is a lime-cured brick made from recycled municipal waste, specifically developed for use on the facade of the new Design Museum Gent extension in the city of Ghent in Belgium. The brick is made from local waste to meet the client’s brief to lower the embodied carbon used in the project’s construction.

These bricks contain 63% waste, and are cured rather than fired. The lime captures CO2 from the atmosphere during the curing, sequestering carbon over the life of the building. The brick also delivers the required strength and resilience to stand up to external conditions. The manufacturing process and the use of locally sourced recycled materials produce a brick, which contains a third of the embodied carbon of a clay brick over a 60-year lifecycle.

Polymer Bricks

How polymer bricks can be joined together as a building material (Image: Flinders University)

Yet another brick made from waste products, the polymer brick is an innovation by the organic chemists at Flinders University who have created lightweight but durable polymer building blocks that can replace clay bricks and do not require mortar for bonding.

"In this study, we tested a new type of brick we can make from waste cooking oil, mixed with sulphur and dicyclopentadiene (DCPD) – both by-products of petroleum refining. All the starting materials are plentiful and can be classified as industrial waste. The bricks bond together without mortar upon application of a trace amount of amine catalyst,” Flinders Professor of Chemistry, Justin Chalker explained.

The polymer brick research team is working with Clean Earth Technologies for further development, and possible commercialisation.

Fly Ash Bricks

Fly ash bricks

Fly Ash Bricks (Image: StructuralGuide.com)

Manufactured from fly ash, an industrial waste created in thermal power plants as a by-product, fly ash bricks are lighter than clay bricks, have more compressive strength, and are made in a more environment-friendly way on hydraulic machines. Their smooth surface eliminates the need for plastering the wall, reducing construction costs.

Fly ash bricks achieve their green credentials by preventing the fly ash waste from being dumped in landfills. Even the manufacturing process, which involves compaction, curing and drying has a low carbon footprint, with no reliance on fossil fuels.

Fly ash bricks absorb less heat, have high durability and low permeability, and offer resistance to fire. The low porosity of these bricks reduces water absorption, minimising dampness on walls. These bricks can be used in both load-bearing and non-load-bearing wall applications, and are particularly recommended for high rise buildings thanks to their lightweight characteristics.

K-BRIQ

K-BRIQ is available in a range of 13 stock colours (Image: Kenoteq)

The highly polluting construction waste is now being recycled back into construction sites in the form of the K-BRIQ, an innovative brick test-launched in August 2019 following 10 years of research at the Heriot-Watt University in Scotland.

Based on circular economy principles, K-BRIQ by Scottish clean tech company Kenoteq seeks to address the demand-supply gap for bricks in the UK market and reduce the reliance on imports. With EU regulations requiring 70% of all construction and demolition waste to be recycled (and none sent to landfill), there is a glut of recycled material available for use, creating opportunities for innovations such as K-BRIQ.

Containing at least 90% recycled construction waste – the highest for any brick – K-BRIQ uses a low-carbon production process that does not require high temperature firing, virgin cement or high volumes of clay. A resource-efficient construction brick made from inert recycled materials, K-BRIQ is recommended as a green replacement for traditional bricks and blocks in exterior and interior environments.

K-BRIQ has a carbon footprint less than 5% of a traditional clay brick, and offers comparable strength and a high thermal mass. The brick is available in a range of 13 stock colours, all made from recycled pigments. K-BRIQ is being commercially launched this year with the company targeting a total delivery of 3 million bricks.

Branko Miletic

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