Title photo: As the need for concrete in Ethiopia's construction industry grows, so too has the National Cement Share Company. Its new plant (above) in the east of the country will increase its production by six times.
If you've visited the Cement page in the section on Causes of Climate Change, then you will already know that If the cement industry were a country, it would be the third largest CO2 emitter in the world - behind China and the US. That's 8% of the world's CO2 emissions or 2.2 billion tonnes annually. If the world continues to ignore this source of CO2 and its impact on global warming, then cement production will cancel out the emission savings gained by closing 314 coal-fired power stations. As pointed out on the cement page, there are countless cement-based megaprojects either under construction or in the planning stage. As developing countries like Ethiopia (title photo) build modern infrastructure - roads, bridges, housing, dams....the list is endless - the demand for cement is going to increase as will the 2.2 billion tonnes of CO2.
Predictions of future cement production are, therefore, extremely concerning (see Fig. 1) given the industry's current emissions. With the current output around 4000 million tonnes (4 billion) predicted to rise and remain at 5000 million tonnes, it is absolutely imperative that the production process is modified in the ways described by Mark Fischetti et al. Those changes need to begin now.
Figure 1
Figure 1
In September 2020, the Global Cement and Concrete Association (GCCA) released a Climate Ambition pledge that aspires, not just to reduce the carbon footprint of concrete but, to achieve carbon neutrality across the industry by 2050. Be mindful that the words 'pledge' and 'aspiration' have plagued progress in cutting emissions since they are not legally binding. So what steps can the industry to take to 'achieve carbon neutrality'?
Cement manufacture generates CO2 from 2 main sources:
60% comes from the heating of limestone in a kiln to convert it into lime, and then clinker. 60-70% of cement kilns use coal for heating, the worst of the fossil fuels in terms of CO2 emissions.
40%: chemical reactions release CO2. (limestone to lime, then lime to clinker).
Mark Fischetti, Nick Bockelman and Wil V. Srubar writing in Scientific American lay out a strategy for cutting CO2 emissions at every stage in the manufacture of cement. In brief summary:
use basalt instead of limestone. Basalt is a non-carbonate rock leading to cement which is more environmentally friendly. In addition, basalt doesn't require the same high temperatures to process it.
burn biomass or waste to heat the kiln; alternatively, use electricity generated renewably.
add a mineralizer such as calcium fluoride to the lime during its fusion to clinker. This will lower the temperature required to achieve the fusion, saving energy.
There are a number of further steps that can be taken to lower emissions and I would encourage anyone interested to read the SciAm article. The overall message is clear: cement can be produced with vastly lowered emissions but this will take strict legislation and investment in converting current cement plants.
Title photo by Gavin Houtheusen/Department for International Development, CC BY 3.0,