The Guardian posted an article this week that attacked the cement industry for its impact on the environment, which drew a quick reply from the Global Cement and Concrete Association (GCCA). Cement production is a CO₂-intensive process and, therefore, it is only right that the cement and concrete industry should come under scrutiny. But equally, the achievements of the sector to date in mitigating CO₂ emissions and the ongoing work in this area should not be overlooked.

Towards zero emissions
Cement is the world's second-largest industrial emitter of CO₂, accounting for ~5-7 per cent of total man-made CO₂ emissions. Moreover, global cement production is also projected to rise to over 5bnt by 2050, driven by population growth, rapid urbanisation and new infrastructure in developing regions such as southeast Asia and sub-Saharan Africa.

To reduce its carbon footprint, the cement industry has developed a range of action plans, including the Cement Sustainability Initiative's (CSI) first technology road map in 2009, which has since been updated with the 'Low-Carbon Transition in the Cement Industry', published together with the International Energy Agency (IEA) in 2018. This report followed the Paris Agreement, negotiated in 2015, which called for action to limit the rise in global temperatures to less than 2°C by 2100.

The landmark 2018 report sets out the technologies and solutions needed to reduce CO₂ emissions from the cement industry by 24 per cent below current levels by 2050, a target which is consistent with the goals of the Paris Agreement. The recommendations focus on the following key areas: energy efficiency, fuel switching, clinker substitution and innovative technologies such as carbon capture and storage (CCS).

These levers, with the exception of CCS, have already delivered an 18 per cent reduction in the global average CO₂ intensity of cement production between 1990-2014, according to The World Business Council for Sustainable Development's (WBCSD) Getting the Numbers Right (GNR) report of 2015.

Going forward, the leading cement producers are continuing this work with a wide range of initiatives, including the exploration of breakthrough technologies, to reach the 2050 target.

HeidelbergCement, in particular, has committed to producing cement with net-zero emissions by 2030 in its northern European factories. Cementa and Vattenfall are setting up a pilot plant in Sweden to achieve zero CO₂ emissions by 2030. The cement industry is ambitious for what it hopes to achieve: Dalmia Cement in India has committed to the production of carbon-negative cement by 2040, supported by extensive investment into renewable energy sources.

Table 1: key indicators for the global cement industry in the 2DS scenario
Indicator	2DS low-variability case
	2014	2030
Clinker-to-cement ratio	0.65	0.64
Thermal energy intensity of clinker (GJ/t clinker)	3.5	3.3
Electrical energy intensity of cement (kWh/t cement)	91	87
Alternative fuel use (% thermal energy)	5.6	17.5
CO2 captured and store (MtCO2/year)	-	14
Direct CO2 intensity of cement (tCO2/t cement)	0.54	0.52
Notes: Thermal energy intensity of clinker does not include any impact related to other carbon mitigation levers beyond improving energy efficiency (eg carbon capture). Electricity intensity of cement production does not include reduction in purchased electricity demand from the use of EHR equipment or any impact related to other carbon mitigation levers beyond improving energy efficiency (eg carbon capture). Alternative fuel use includes biomass, and biogenic and non-biogenic wastes. Direct CO2 intensity refers to the gross direct CO2 emissions, after carbon capture. Source: Technology Roadmap - Low-carbon transition in the cement industry (2018)

Fuel switching
The cement industry is also moving away from fossil-based fuels towards higher alternative fuel (AF) use. In Europe AFs meet 43 per cent of the sector's fuel requirements, compared to 15 per cent in North America, eight per cent in China, South Korea and Japan, and three per cent in India, according to research by Ecofys. Europe's cement association, CEMBUREAU, believes waste fuel has the potential to replace 60 per cent of traditional fuels in the medium term and potentially up to 95 per cent. Globally, AF utilisation is expected to reach 17.5 per cent by 2030, according to the CSI.

Clinker substitution and low-carbon cements
Substituting Portland clinker with fly ash, ground granulated blastfurnace slag (GGBS) or limestone can also save 3.7GJ and 0.83t of CO₂/t of clinker displaced, reports the IEA/CSI. To date, clinker substitution has contributed on average to a 20-30 per cent drop in CO₂ emissions per tonne of cement produced compared to the 1980s. The 2018 roadmap sets the ambitious target of an average global clinker ratio of 0.60 by 2050 from 0.65 in 2014.

The challenge here is the availability of substitutes. It would need 2bnt of clinker substitutes to be consumed in 2050, almost 40 per cent more than what is consumed today. Meanwhile, the global availability of clinker substitutes, such as fly ash and GGBS, is forecast to decline by 16 per cent of cement production by 2050.

Meanwhile, the industry is working hard to develop low-carbon cements, such as Vicat’s Alpenat^® and LafargeHolcim's Aether cement. Further research is also being carried out on belite-rich Portland clinkers, belite clinkers containing ye'elimite, as well as hydraulic, carbonate calcium silicate and magnesium-based clinkers. Geopolymers, alkali-activated binders and clays are also options considered.

Energy reduction
The cement sector is the third-largest industrial energy consumer in the world and is responsible for seven per cent of industrial energy use. Producing cement using the current best available technology (BAT) results in thermal energy consumption of around 2.9GJ/t of clinker produced. This has fallen from 3.5GJ/t of clinker in 2014, with India's plants leading the way, achieving thermal energy consumption below 3GJ/t of clinker. Again, while improvements can be made – advances in artificial intelligence in plant optimisation, for instance – the expectation is that improvements in thermal and electrical energy are constrained by the limits of available technology.

Carbon pricing
The EU Emissions Trading Scheme (ETS) enters Phase IV in 2021-30. Following reform to the allocation system, carbon prices are expected to exceed EUR30/t. This additional cost will force a reduction of cement production in Europe and thereby achieve the aim of lowering the EU’s CO₂ emissions. However, perversely, it likely to result in carbon leakage, with clinker produced in north Africa and Turkey used to supply European plants. In the end, factoring in additional shipping and transportation, the net CO₂ of cement consumed in Europe could be higher.

Concrete
In assessing the impact of cement on climate change and sustainability, we should also consider the significant positive attributes of concrete, which consumes 250-300kg cement/m³. Studies into the life-cycle of concrete by the highly-respected Massachusetts Institute of Technology (MIT) reveal it to offer a low-cost and low-carbon alternative to competing materials.

Concrete’s high thermal mass properties result in lower operational carbon emissions of a building over its lifetime, which is particularly important given that the operation of buildings and homes accounts for more than 40 per cent of CO₂ emissions each year.

As a product, it is fully compatible with the concept of the circular economy. Concrete can be 100 per cent recycled after demolition and the co-processing of AFs in the cement industry is providing a more sustainable future.

Ultimately, concrete is a highly versatile and durable material with a high technical performance that is difficult to match by alternatives. This has not made the cement industry complacent: as this article attempts to show, the industry is working hard to reduce emissions and will continue to do so.

Published under Cement News