Journey of cement as a sustainable construction material
The global cement industry space is as big as $300 billion, almost half of that is in China, but the real distinctive way of looking at the space is to see how much of this is “sustainably” organised, as most of it is not.
The two most dominant regions that are organising themselves sustainably is EU and China, the former is doing it through legislations and cement companies have to buy carbon credits, the price of which has moved to the stratosphere, so the financial incentives are driving it as less emissions can only reduce this impact. The latter is cracking down on all polluting industries and emission norms remain stringent for all industries, including cement.
The rest of the world do not have a concerted way of incentivising the sustainability journey in cement, although every government wants to limit the impact of emissions and there are norms set in this regard. These norms however are far short of making the journey for a net zero kind of impact, which essentially means that cement as a construction material will not add any net emission of CO2 to the atmosphere either during production or in sourcing of inputs or during transportation and use. This is a very tall task for three reasons.
The first reason is that the conversion of limestone to clinker itself is the fundamental driver of the bulk of the CO2 emissions as the molecular structure changes. The second most dominant factor for emissions is in the use of energy for heating of the limestone mix and the emissions that stem from the logistics sector on the inbound and outbound to move materials. The third is the entire supply chain of cement including all sources of direct and indirect materials add to the woes of emissions generated by the partners in the process. Thus making and distribution of cement becomes the text book case for emissions and sustainability.
The cement to CO2 mix is simple to understand that for every ton of cement produced 0.6 tons end up as CO2 in the atmosphere. So if the world produces 4.3 billion tonnes of cement, 2.6 billion tonnes of CO2 is emitted by the industry globally, out of which 1.82 billion tonne is only in the conversion of limestone to clinker.
This natural process of production of cement is where all attention is currently devoted as the rest has solutions like using solar or wind as energy source, waste heat recovery systems or electrification in transportation and improvement of efficiencies of all kind in the entire supply chain. But the basic production process of cement needs a breakthrough look if net zero targets are to be met.
This journey of reducing the emissions for producing cement started in the early part of 2000, when Polish cement manufacturers started using more fly ash as raw material inputs while grinding clinker to cement, this reduced the clinker in cement. The percentage use of fly ash moved to plus 30 per cent when it drew the world’s attention as it meant that overall emission reduction could touch 30 per cent of 70 per cent or 21 per cent.
The same started to happen with use of slag in slag based cement where the percentage use touched more than 50 per cent, which meant that 50 per cent of 70 per cent, or 35 per cent reduction in emission for the overall cement industry.
Thus alternate use of raw materials in the grinding, slag and fly ash helped to reduce CO2 emissions from close to 600 kg per ton of cement to 550 kg per tonne of cement now. The question now is to look at the balance, which is the very production of clinker through the natural process of conversion of limestone through application of heat, which releases CO2 to the atmosphere.
The current technologies where the attention has been drawn is towards carbon capture processes that will disallow release of carbon dioxide (CO2) to the atmosphere. The first one of its kind is the strategy of using CO2 for permanent storage during the production of concrete, where CO2 molecules are injected when cement is mixed with water to create concrete and it permanently stores CO2 to harden the concrete forever.
Today the world over pre-cast or pre-fabricated concrete blocks are the new norms of the day and this technology can be used to absorb the CO2 molecules to harden the concrete and this would prevent the release of CO2 to the atmosphere. This is the future use of CO2 not only from the emissions coming from the Cement industry but also from any industry that releases CO2 and it helps in the carbon credit offset for all industries as well.
Thus carbon capture, sequestration and its use in existing or future products is where the world’s attention is devoted; the efficiency improvement programs, use of waste heat recovery from the process by extracting from the cooler, use of alternate materials during grinding, etc. all comes on top.
If the world’s incentive systems are well coordinated, the pace at which these programs are run will only move to the next gear, as the investments can only pay back to offset the carbon credits.
The cement-concrete industry on the other hand by providing a useful carbon capture solution in its product would have the right for a premium that customers would be willing to pay as responsibility for the environment becomes mandatory for all.
ABOUT THE AUTHOR:
Procyon Mukherjee is an ex-Chief Procurement Officer at LafargeHolcim India.