June 2024

Introduction

The construction industry is a significant contributor to global carbon dioxide (CO2) emissions, primarily due to the production of traditional Portland cement. Cement production alone accounts for approximately 5-8% of global CO2 emissions, making it the third-largest industrial source of CO2 emissions after fossil fuels and land-use change (Andrew, 2017). This translates to about 900 kg of CO2 emitted for every ton of cement produced (Benhelal et al., 2013). Given the extensive use of cement, finding sustainable alternatives is crucial to reducing the industry’s carbon footprint.

What is Green Cement?

Green cement refers to cement produced using carbon capture and storage (CCS) technologies. These technologies capture CO2 emissions generated during cement production and integrate them back into the cement, thus reducing the overall carbon footprint.

The Technology Behind Green Cement

Several carbon capture technologies are used in the production of green cement, including:

• Oxy-fuel Combustion: Burns fuel in pure oxygen instead of air, producing a CO2-rich exhaust that is easier to capture (Voldsund et al., 2019).
• Calcium Looping: Uses calcium oxide to absorb CO2, which is then released and captured during calcination (Atsonios et al., 2015).
• Amine Scrubbing: Involves chemical absorption of CO2 using amines, which are then regenerated to release and capture CO2 (Li et al., 2013).

Benefits of Green Cement

Green cement offers several benefits over traditional cement:

• Environmental Benefits: Significant reduction in CO2 emissions, contributing to climate change mitigation. For instance, the LEILAC project has shown potential to capture 95% of a cement plant’s process CO2 emissions (Hills et al., 2017). And new cement has net zero carbon emissions.
• Economic Benefits: Potential cost savings from reduced carbon taxes and credits, and the possibility of using less energy-intensive production processes. The cost of CO2 avoidance can range from €60 to €115 per ton, depending on the technology used (Markewitz et al., 2019).
• Performance: Green cement can perform comparably to traditional cement in terms of durability and strength (Dixit et al., 2021).

Challenges and Limitations

Despite its benefits, the adoption of green cement faces several challenges:

• Technological Challenges: The need for advanced and reliable carbon capture technologies that can be retrofitted to existing plants (Plaza et al., 2020).
• Economic Challenges: High initial costs and financial risks associated with deploying new technologies (Li et al., 2013).
• Scale and Infrastructure: The requirement for substantial infrastructure to transport and store captured CO2 (Voldsund et al., 2019).

Case Studies and Real-world Applications

LEILAC Project

The LEILAC (Low Emissions Intensity Lime and Cement) project aims to apply a revolutionary carbon capture technology to the cement and lime industries. It aims to enable the capture of unavoidable process CO2 from limestone calcination with no energy cost and no extra capital cost, apart from compression. Heidelberg Cement’s Lixhe plant in Belgium has launched an evoZero® cement, with a net zero carbon footprint thanks to carbon sequestration. This innovative cement incorporates carbon capture and storage technologies to trap the CO2 emitted during production. As well as using sustainable materials, it makes a significant contribution to reducing CO2 emissions, taking an important step towards greener, more sustainable construction.

Ultra-High Performance Concrete (UHPC)

Research has demonstrated the potential of carbon capture in ultra-high performance concrete using pressurized CO2 curing. This method significantly improves the degree of carbonation and the environmental performance of the concrete, making it a viable option for green construction (Dixit et al., 2021).

Future Prospects

Future research and innovation are crucial for the widespread adoption of green cement. Areas of focus include:

• Improving Carbon Capture Efficiency: Enhancing existing technologies and developing new methods for more effective CO2 capture. Research is ongoing to improve the performance and reduce the costs of various capture technologies, such as facilitated transport membranes and calcium looping (Ferrari et al., 2021).
• Economic Viability: Reducing costs through technological advancements and economies of scale. Continued innovation in production processes and materials is expected to lower the costs of green cement, making it more competitive with traditional cement (Li et al., 2013).
• Policy and Incentives: Implementing supportive policies and financial incentives to encourage the adoption of green cement technologies. Governments and regulatory bodies need to establish frameworks that promote the use of green cement through subsidies, tax incentives, and stricter emissions regulations (Voldsund et al., 2019).

Conclusion

Green cement represents a significant step towards sustainable construction, offering a viable solution to reduce the carbon footprint of the cement industry. Continued research, innovation, and supportive policies are essential for realizing the full potential of green cement and achieving a more sustainable future.

References

• Andrew, R. (2017). Supplementary material to “Global CO2 Emissions from Cement Production.” Earth System Science Data, 10, 195-217.
• Benhelal, E., Zahedi, G., Shamsaei, E., & Bahadori, A. (2013). Global strategies and potentials to curb CO2 emissions in cement industry. Journal of Cleaner Production, 51, 142-161.
• Hills, T., Sceats, M., Rennie, D., & Fennell, P. (2017). LEILAC: Low Cost CO2 Capture for the Cement and Lime Industries. Energy Procedia, 114, 6166-6170.
• Dixit, A., Du, H., & Pang, S. (2021). Carbon capture in ultra-high performance concrete using pressurized CO2 curing. Construction and Building Materials, 288, 123076.
• Li, J., Tharakan, P., Macdonald, D., & Liang, X. (2013). Technological, economic and financial prospects of carbon dioxide capture in the cement industry. Energy Policy, 61, 1377-1387.
• Markewitz, P., Zhao, L., Ryssel, M., Moumin, G., Wang, Y., Sattler, C., Robinius, M., & Stolten, D. (2019). Carbon capture for CO2 emission reduction in the cement industry in Germany. Energies.
• Plaza, M., Martínez, S., & Rubiera, F. (2020). CO2 capture, use, and storage in the cement industry: State of the art and expectations. Energies.
• Ferrari, M., Amelio, A., Nardelli, G., & Costi, R. (2021). Assessment on the application of facilitated transport membranes in cement plants for CO2 capture. Energies.