Decarbonization of the cementitious materials cycle
The journal of Industrial Ecology published an article on decarbonizing the cementitious materials cycle and activities directly related to cement spanning extraction through to end of life. It relates measures, which comprise emissions, energy, and material efficiency, to the European policy landscape.
Industrial greenhouse gas (GHG) emissions accounted for ∼30% of the global total in 2010. To limit global warming to 1.5°C above pre-industrial levels, as per the Paris agreement, industrial emissions are required to reduce by 54−91% (relative to 2010 levels) by 2050.
The cement industry accounted for ∼23% of industrial emissions globally, or ∼8% of total global emissions, in 2012. As with total industrial emissions, emissions from the cement industry are projected to increase under a business-as-usual scenario, due to rising global demand for cementitious material (CM) products (i.e., cement, mortar, concrete). Therefore, decarbonizing the cement industry, here defined as reducing its emissions to net zero, presents a significant challenge.
This challenge is
-technical, for example, due to the high energy and emissions intensities of the production processes,
-economic, for example, due to the globalized and relatively low-profit-margin nature of CM products.
Production will increase
Cement is the key precursor of mortar and concrete, the latter being the most used synthetic material on Earth. It reacts with an activator (e.g., water) to form the relatively strong and durable matrix, known as a “binder,” that glues aggregate (sand, gravel) particles together in these materials. Cement is essential to socio-economic development, through buildings, for homes, education, business, and healthcare, and other infrastructure, for transport, sanitation, and energy.
Accordingly, global cement demand is expected to increase in the future, compounded by increasing population and urbanization. Global annual cement production almost tripled from 1994 to 2014, and is expected to be 12–23% higher still by 2050 under a business-as-usual scenario. This increase in production is anticipated to come mainly from lower-income countries. However, concrete will remain a key building material in higher-income countries due to its relatively low production cost and abundant raw materials.
Cement also facilitates decarbonization of other industries and end-use sectors through use of concrete in construction, for example, wind turbines, dams, and buildings with low operational energy consumption. European cement production is expected to increase by up to ∼10% by 2050.
Portland cement(PC)-based concrete has a low embodied emissions intensity by mass compared to other construction materials such as steel. However, such CM products are used at such a massive scale that they account for ∼8% of total anthropogenic emissions and ∼23% of industrial emissions globally. PC clinker production accounts for most of the embodied emissions in PC concrete. It is one of the most difficult industrial processes to decarbonize, since fundamental “process emissions” account for ∼50% of PC production emissions.
The focus on whole CMs cycle
Careful policy intervention is thus essential in decarbonizing the global cement industry, and other industries which share similar challenges. This is particularly relevant in high-income countries, where development and deployment of low-emissions technologies must be stimulated while avoiding “carbon leakage”.
Decarbonization measures with significant potential exist along the entire CMs cycle, although upstream, energy, and emission efficiency measures are better quantified than downstream and material efficiency measures. Notably, the decarbonization potentials of recycling technologies and the ways in which technological advancements may transform the CMs cycle and thus the stocks, flows, and processing of materials, as well as effectiveness of decarbonization measures, are poorly understood.
The CMs cycle consists of the following main processes:
(1) extraction (of primary materials);
(2) production (of cement and aggregate);
(3) manufacturing (of concrete and mortar);
(4) use;
(5) end-of-life.
Higher-income countries have historically focused emissions-related policy on promoting energy efficiency (e.g., cement kiln efficiency) and “emissions efficiency” (e.g., carbon capture and storage/utilization, CCS/U) at the cement production stage. However, the cost of further emission reductions through such measures can be high, for example, CCS (which would result in a 70–115% increase in cost per ton cement produced), and rates of implementation can be slow.
Expanding the focus of emissions-related policy from the production stage to the whole CMs cycle can mitigate this problem. Recent studies highlight the following benefits of such a systems approach: reduced cost, less urgency for technological development, and a wider, less concentrated distribution of effort. Notably, a systems approach includes implementation of material efficiency measures.
