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Appendix G: CO2 for concrete curing
New technologies and methods for cement production are reducing the production of CO2 emissions from conventional Portland cement. Technologies such as the Calera process produce raw materials which may be used to supplant a portion of Portland cement. High tech firms such as Novacem (London), TecEco (Australia), C-Fix (Holland) and Calix (Australia) are new emerging competing companies focused on producing carbon negative cement by eliminating or reducing the carbon emissions (that would otherwise be generated and emitted during manufacture of conventional Portland cement) and/or by absorbing CO2 from the atmosphere during the curing process.
Unique from the companies aforementioned, Carbon Sense Solutions (Canada) is seeking to use a point source of CO2 to limit the need for heat and steam curing of precast concrete products. Instead of the traditional energy intensive steam curing technologies, The Carbon Sense concrete curing process consumes CO2 from onsite flue gases and local combustion sources to cure precast concrete products, with claimed equal material performance to traditional the curing process.
Extensive design and industrial testing is underway by Carbon Sense Solutions Inc. (CSS) to minimise the installation and operation risks in readiness for rapid acceleration from demonstration to commercial scale.
Carbon Sense Solutions Inc. (CSS) is partnering with industry and the government to demonstrate and optimise the concrete curing process utilising CO2 instead of heat and steam at an industrial scale. Extensive design and industrial testing is underway to minimise the installation and operation risks.
Currently CSS has funding secured for its first full scale demonstration plant to be implemented in winter 2011. Commercialisation of the technology is planned for 2012.
CSS has indicated that up to 120kg of CO2 per tonne of precast concrete is sequestered during the curing process. However, this figure may represent the total CO2 offset that the technology can deliver.
Concrete curing is a technology used by manufacturers of precast concrete worldwide. The main potential for the CO2 curing method would be through the displacement of the traditional methods by existing manufacturers. Since, The flue gas produced by the concrete production process itself is a suitable source of CO2, countries in which there exists a carbon scheme hold the most potential.
Size of market
Global cement production in 2009 amounted to 2.9 billion tonnes (Rusmet 2010), with corresponding concrete production well in excess of 10 billion tonnes. In the United States and Canada, annual cement consumption by the four main concrete products (masonry block, paving stone, cement board and fibreboard) is approximately 14 million tonnes (30 billion lb). If all of these products were carbonation treated, The net annual storage of CO2 in concrete could reach 1.8 million tonnes (4 billion lb) using recovered CO2 (at a net efficiency of 87.1 per cent) and 0.98 million tonnes (2.1 billion lb) using flue gas (at a net efficiency of 84.0 per cent)(Shao et al 2010).
The main driver of this technology is likely to be the price and demand of concrete. A further driver of implementation of the technology will be the existence of a carbon trading scheme.
Level of investment required (to advance the technology)
Currently, CO2 recovery costs about US$165/tonne (US$150/tonne) (US DOE, 2010). At this price, The CO2 required for curing will cost about US$0.08 per masonry block (200 × 200 × 400 mm (8 × 8 × 16 in.) nominal size concrete masonry unit). Although the production of steam for curing currently costs only about US$0.02 per block, it is anticipated that the relative cost of CO2 will decrease as recovery technologies develop and carbon storage credits affect the markets (Shi et al 2009).
Potential for revenue generation
Use of CO2 for curing as an alternative to current methods is unlikely to be more profitable since research suggests that concrete cured under this technology will not have a technological advantage over traditional methods and therefore the concrete is unlikely to be able to be sold at a premium. The main economical benefit is derived from any cost savings which can be made through using CO2 as opposed to an alternative; however research suggests that with the current costs of carbon capture, The technology is more costly.
The cost of the technology will be sensitive to the relative costs of CO2 capture and those of materials required for alternative curing methods.
Technology is in early stages of development however there is potential for the technology to be commercialised relatively easily as concrete curing process already exists in concrete production. Furthermore, research suggests that the flue gas produced from concrete plant itself may provide a suitable CO2 source therefore reducing implementation costs. The commercial benefit in this case will be further incentive provided by the existence of a carbon trading scheme.
Producers will benefit from energy and water reductions resulting in cost savings and efficiency gains.
Process is easily retrofitted, requiring targeted modifications to existing plant machinery with minimal disruption to existing processes.
It is claimed that the use of CO2 results in an accelerated curing process with lower temperatures required.
The concrete sector operates within a highly competitive commodity market with limited capital to invest in new technologies.
The change in production method (curing process) must not compromise material performance as the material performance is governed by industry standards (e.g. ASTM, CSA).
Scientific American (2008) Cement from CO2: A concrete Cure for Global Warming? http://www. scientificamerican.com/article.cfm?id=cement-from-carbon-dioxide Last viewed 10/06/2010, last updated 07/08/2008.