Tag: Carbon storage

Counting on … day 87

16th April 2024

Green cement – part 2

As part of the need to reduce all greenhouse gas emissions to address the climate crisis, reducing emissions from cement production is essential. 

50% of the emissions come from the release of carbon dioxide as a byproduct during the clinker making process. One solution is carbon capture- capturing the CO2 before it escapes into the atmosphere, pressurising it to a liquid which is injected into rock strata deep underground.  This technology has yet to be developed for use at an industrial scale. 

Another solution is to replace the limestone with an alternative that produces less CO2 – such as magnesium oxide mixed with magnesium chloride solution. However such alternative cements may not have all the attributes of cement when in use – different construction methods may be needed.

40% of the emissions are attributable to the energy needed to heat the clinker kilns. Switching to renewable energy to replace coal is one solution but requires considerable investment in green electricity production and distribution. 

Using materials other than limestone – such as volcanic rock – that can produce clinker at lower temperatures is another possible solution. Another alternative is to replace a proportion of the cement with an alternative binder such as ground granulated blast furnace slag or pulverised fly ash. Again this may alter the properties of the cement and require different construction methods.

10% of the emissions comes from energy used in mining and transporting the raw materials. Energy efficiency and the use of renewable energy will be a way forward.

Further reading –https://theconversation.com/green-cement-a-step-closer-to-being-a-game-changer-for-construction-emissions-126033

(https://theconstructor.org/concrete/green-cement-types-applications/5568/

Counting on … day 72

22nd March 2024

Carbon sequestration is a formal name given to the processes by which carbon is captured from the atmosphere and stored on a long-term basis. Such long-term storage might include peat bogs, forests, kelp beds etc and may be referred to as ‘carbon sinks’.

Carbon sequestration can be used as a means of  mitigating the effects of climate change. This can be biologically by, for example, planting more forests, restoring peat bogs and wetlands, and re-establishing kelp meadows. This natural sequestration can be enhanced, in the case of forests, by using felled timber to make items such as buildings, furniture etc and keeping those items for hundreds of years. However growing trees for timber needs to be carefully managed to a) maximise the carbon captured by the growing tree, and b) to maximise the flourishing of biodiversity.

Carbon can also be sequestered geologically if the CO2 can be captured  eg from a cement factory. Then the CO2 “can be compressed to ≈100 bar into a supercritical fluid. In this form, the CO2 could be transported via pipeline … and  injected deep underground, typically around 1 km, where it would be stable for hundreds to millions of years.” (https://en.wikipedia.org/wiki/Carbon_sequestration)