New building material made from waste sequesters carbon

A new type of cement made from recycled materials has the ability to sequester carbon dioxide, allowing economic growth to go hand in hand with climate change mitigation, claims an Australian scientist.

The new Eco-cement, developed by Tasmanian inventor John Harrison of TecEco Pty Ltd, and made from a combination of waste materials, predominantly fly ash, with Portland cement and magnesia, has now become commercially available. As the cement sets it absorbs carbon dioxide, says Harrison.

Uses for the cement include bricks, blocks, paving slabs, mortars, airstrips and roads. The material can also be used for immobilising toxic wastes, he says.

Harrison stresses concern at projects to sequester carbon in natural ocean ecosystems, such as through creating artificial algal blooms. He notes that the use of such schemes makes no sense when it is possible to store a large proportion of man-made carbon dioxide in the built environment.

There is more good news with regard to cost of the material compared to conventional cement. “The price should be lower because of the lower energy costs of production,” Harrison told edie. “Including the negative cost of wastes – people will pay to cart it away – and carbon credits, and [in] the longer term [it will be] much cheaper.”

Currently, around 1.65 billion tonnes of Portland cement is produced around the world, says Harrison. If 80% of this was substituted for eco-cement, there would be a net sequestration of 1.5 billion tonnes of carbon dioxide, with emissions from manufacture taken into consideration, he claims.

The material is also strong, with weathering from normal carbonic acid rain not affecting the carbon dioxide balance. However, nitric acid and sulphuric acid will, Harrison admits.

“Any materials that take little energy to make, are cheap, strong, set by absorbing CO2, and can include a large proportion of wastes have to be an important part of the future of our existence on this planet,” said Harrison. “This is particularly so if the earth is to provide the resources for poorer nations to achieve the higher standards of living employed by the developed nations.”

“Green building technologies offer a way for all countries to reduce greenhouse gas yet improve their standard of living, and at the same time bring the focus on sequestrations to the cities where more people can be involved in positive action,” he said.

Professor Fred Glasser of the University of Aberdeen in Scotland, and a world leading materials scientist, is quoted as describing the eco-cement as a “world first”. He says that it “represents one of the few recent advances in inorganic cements which are suitable for large volume production.”

Research by the UK Environment Agency published in July revealed that incinerator bottom ash can be a potentially valuable secondary aggregate, particularly if there is governmental guidance on acceptable contaminant levels (see related story).

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