Making more than 4 billion tons of cement each year is responsible for about 8% of CO2 emissions worldwide. We don't have a substitute for it, but there are ways to cut those emissions that scientists and industry are exploring, and even to sequester CO2 in making cement.
I have been wanting to get to this for some time. Going to five days a week opens up that opportunity, and many others.
BBC: Climate change: The massive CO2 emitter you may not know about
Not only does the production of Portland cement involve quarrying - causing airborne pollution in the form of dust - it also requires the use of massive kilns, which require large amounts of energy.
The actual chemical process of making cement also emits staggeringly high levels of CO2.
Below, we look at several proposed solutions. I make no representations about which will be commercially viable, how fast they can be adopted, and other critical variables.
The BBC story continues:
The sector has made progress - improvements in the energy-efficiency of new plants and burning waste materials instead of fossil fuels has seen the average CO2 emissions per tonne of output fall by 18% over the last few decades, according to Chatham House.
The newly-established Global Cement and Concrete Association (GCCA), currently representing about 35% of the world's cement production capacity and with a focus on sustainable development, was at COP24.
Making Cement
The main ingredient in cement is called clinker. It is made by heating ground limestone (calcium carbonate) and clay. The simple chemical equation is
CaCO3 + heat → CaO + CO2
More than half of the mass of the limestone has been released as CO2.
- Raw materials, mainly limestone and clay, are quarried and crushed
- They are ground and mixed with other materials - such as iron ore or ash
- They are fed into huge, cylindrical kilns and heated to about 1,450C (2,640F)
- The process of "calcination" splits the material into calcium oxide and CO2
- A new substance called clinker emerges as marble-sized grey balls
- The clinker is cooled, ground and mixed with gypsum and limestone
- The cement is transported to ready-mix concrete companies
Science and Technology
Scholarly articles for concrete co2 capture
Google Scholar returns more than 51,000 hits, of which these are the top three.
CO2 capture using fly ash from coal fired power plant … - Siriruang - Cited by 33
Highlights
- Fly ashes can capture CO2 via surface adsorption and carbonation reaction.
- Fly ashes after CO2 capture can reduce free CaO content in the fly ash.
- The physical properties of specimens were compared with reference and standards.
- The expansion of mortars using fly ash after CO2 capture is greatly reduced.
- Fly ashes after CO2 capture can used as mineral admixture for concrete.
We have developed a new ecological concrete which can achieve a CO2 emission level below zero by capturing CO2. This concrete is based on two typical features. One of the features of this concrete is using a special admixture (the γ phase of dicalcium silicate: γ-2CaO.SiO2) instead of cement. This material has a very low level of CO2 emissions and hardens the concrete by reacting with CO2. The other feature of this concrete is capturing the CO2 contained in the exhaust gas from thermal power stations. In this paper, we set forth the concepts of the development and various results of examination of the ecological concrete. This ecological concrete is named CO2-SUICOM (CO2 Storage under Infrastructure by Concrete Materials).
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The potential for using calcium silicate concrete to sequester CO2 and simultaneously develop strong and durable concrete building products is studied. It is the calcium compounds in cement that react with CO2 through the early-age carbonation curing, forming geologically stable calcium carbonates. Both type 10 and type 30 Portland cements were investigated as CO2 binders in concretes with 0%, 25%, 50%, and 75% quartz aggregates and lightweight aggregates. The sequestration took place in a chamber under 0.5 MPa pressure at ambient temperature for a duration of 2 h; a 100% concentration of CO2 was used to simulate the recovered CO2 from flue gas. The CO2 uptake was quantified by direct mass gain and by infrared-based carbon analyzer, and the performance of the carbonated concrete was evaluated by its strength. A CO2 uptake of 9%�16% by binder mass was achieved in 2 h. The X-ray diffraction spectra showed the presence of strong calcite peaks and a total absence of Ca(OH)2. The 2 h carbonation strength exceeded the 7 d hydration strength. The calcium silicate concrete approach is shown to be feasible for CO2 sequestration and would result in technical, environmental, and economical benefits.Key words: CO2 sequestration, concrete, carbonation curing, calcium carbonates, strength.
Jul 6, 2018 - CarbonCure's system takes captured CO2 and injects it into concrete as it's being mixed. Once the concrete hardens, that carbon is ...
The CarbonCure Technology injects a precise dosage of carbon dioxide (CO 2) into ready mix concrete and concrete masonry products, where the the CO 2 ...
Dec 6, 2017 - This article is part of The Race to Zero Emissions series investigating carbon-capture technology.
In the new book "Designing Climate Solutions: A Policy Guide to Low-Carbon Energy," my co-authors and I identify a suite of policies such as carbon pricing, industry efficiency or emissions standards, and government research and development (R&D) support to help ensure the necessary technologies exist and incentivize their use.
Our research shows (PDF) that depending on the extent thermal fuel supply is decarbonized, a CO2 capture rate between 53 percent and 80 percent will make cement carbon-neutral, and higher CCS capture rates achieve net carbon-negative cement. This offers the prospect of a world where simply constructing buildings and infrastructure reduces atmospheric CO2 concentrations and contributes to the fight against climate change.
The authors go into much more detail than we can cover here.
Scientific American: Cement from CO2: A Concrete Cure for Global Warming
While Calera's process of making calcium carbonate cement wouldn't eliminate all CO2 emissions, it would reverse that equation. "For every ton of cement we make, we are sequestering half a ton of CO2," says crystallographer Brent Constantz, founder of Calera. "We probably have the best carbon capture and storage technique there is by a long shot."
Cement Producers Are Developing a Plan to Reduce CO2
The World Cement Association recently held its first-ever global climate change forum, where industry leaders and scientists discussed strategies to reduce the industry's carbon footprint. It will help inform the development of a climate action plan, which the WCA intends to release in September, aimed at outlining pathways for low-carbon cement production.
Decarbonizing the provision of cement and steel will require major changes in manufacturing processes, use of alternative materials that do not emit CO2 during manufacture, or carbon capture and storage (CCS) technologies to minimize the release of process-related CO2 to the atmosphere
COP25 Day 2
I got no response to my Diary on COP25 yesterday, so I am not doing one today. Not that anything actually happened to signal progress in national commitments.
Greta Thunberg arrives in Lisbon for COP25 after sailing across Atlantic
COP25: WWF and Prado Museum use art to show climate change
Meet the Big Polluters Sponsoring COP25
For Santiago, the Chilean government had secured the financial backing of the country’s mining, manufacturing and employers associations. For Madrid, the acting Minister for Ecological Transition, Teresa Ribera, has knocked on the doors of the large companies of the Ibex35 and the Spanish employers' association for the financing of the Conference. An excellent opportunity for "greenwashing" of the main companies emitting greenhouse gases and responsible for numerous socio-environmental conflicts around the world.
COP25: ‘Signals of hope’ multiplying in face of global climate crisis, insists UN's Guterres
Efforts so far have been “utterly inadequate” and the Paris Agreement commitments still mean a rise of 3.2 degrees unless more drastic action is taken, said the UN chief, but 1.5 degrees “is still within reach.”