Cementing a green future

A green noose is slowly closing in on the cement industry, where production currently represent about 5% of global CO2 emissions.

Last month, the World Business Council for Sustainable Development (WBCSD) and the International Energy Agency (IEA) published a road map that calls for strong national policies as well as actions to develop commercially viable carbon capture and storage technologies to reduce global CO2 emissions from the cement industry.

The cement roadmap outlines a possible transition path for the industry to make continued contributions towards a halving of global CO2 emissions by 2050. It estimates that the cement industry could reduce its direct emissions 18% from current levels by 2050.

The report also mentioned a number of low-carbon or carbon-negative cements currently being developed by start-up companies such as Novacem, Calera, and Calix who are expecting to build pilot plants in 2010/11. The report also mentioned geopolymer cement as another technology that have already been commercialized in small-scale facilities, but have not yet been used in large-scale applications.

Geopolymer cement utilises waste materials from the power industry (fly ash, bottom ash), the steel industry (slag), and from concrete waste, to make alkali-activated cements. This process was reportedly developed in the 1950s.

Novacem’s cement, meanwhile, is based on magnesium silicates rather than limestone (calcium carbonate) as is used in Ordinary Portland Cement. Novacem estimates that for every tonne of ordinary Portland cement replaced by Novacem cement, around 0.75 tonne of CO2 could be captured and stored indefinitely in construction products.

Calera’s cement is a mixture of calcium and magnesium carbonates, and calcium and magnesium hydroxides produced by bringing sea-water, brackish water or brine into contact with the waste heat in power station flue gas, where CO2 is absorbed, precipitating the carbonate minerals. Last December, Calera and Bechtel Power Corporation formed an alliance to develop and construct facilities using Calera’s carbon capture technology.

Australia-based Calix owns a minerals processing technology called Flash Calcination, where its cement is produced in a reactor by rapid calcination of dolomitic rock in superheated steam. The CO2 emissions can be captured using a separate CO2 scrubbing system.

Another cement company from Mexico, Cemex, announced last month its strategies to tackle climate change. Cemex made a commitment to reduce CO2 emissions per metric ton of product 25% from the 1990 levels by 2015.

In cement production, the company said it is using a smaller percentage of the energy intensive ingredient clinker in their end product by substituting clinker with alternative materials such as by-products from other industries, primarily fly ash from coal-fired power stations and blast furnace slag from the steel industry.

Cemex is also involved in carbon capture projects and has even received a $1.1m grant from the US Department of Energy (DOE) last October to develop technology for capturing and storing carbon dioxide emissions at one of CEMEX’s US cement plants.

5 Responses to Cementing a green future

  1. Paul Kidd 21 January, 2010 at 5:48 pm #

    Calera is basically a process, and not a cement. And subsequently, the Calera process will generate calcium carbonate which may be added to Portland cement (after drying, screening, grinding and classification). Calcium carbonate has no hydraulic properties as such.
    Again, Calix is an industrial process rather than an alternative cement.
    Novacem has potential but there may be durability issues down the track.
    Geopolymers show great promise however high pH liquid activators and elevated curing conditions are holding them back. However dry powder activators and ambient curing are definitely possible.
    Another alternative cement not mentioned is ceramic based cements. These cements are already used extensively in many applications including road surfacing. Ceramic based binders can be made from industrial waste products and do not require dangerous activators of high temperature curing.



  2. Ben 28 October, 2010 at 2:49 am #

    I am starting a geopolymer business and am looking for folks to do projects with or get involved. What are you up to? You sound like you have a good background knowledge in this field.

  3. charo 24 January, 2011 at 10:43 am #

    that’s sound interesting… but I didn’t find something else about the “ceramic based binders” do you have some references? that sound good for many wastes we are generating in many industries… please can you give us some names of universities or companies working on this field!.. thanks!

  4. Paul Kidd 24 January, 2011 at 8:53 pm #

    Hi Ben
    Sorry I missed this before.
    I have worked in a technical & R&D role in cement alternatives for the last 10 years. Before this in cement manufacture.
    Please feel free to contact me at:


  5. Doris de Guzman 16 April, 2013 at 7:42 pm #

    Hi Paul,
    Thanks for the clarification on Calera and Calix, and the additional comment on ceramic-based cements!

Leave a Reply