Cement Industry Adopts MCDM for Net-Zero Emissions

By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.Oct 21 2024

A recent study in Engineering Proceedings has proposed a framework that integrates Shannon's entropy with multi-criteria decision-making (MCDM) approaches to help the cement sector achieve net-zero emissions and sustainability. The researchers used four MCDM methods to rank different energy efficiency alternatives for cement production.

Background

The cement industry, known for its high energy consumption, accounts for about 12-15 % of all industrial energy use. Cement production involves combining iron ore, alumina, limestone, silica, and other trace elements, which are then heat-treated for chemical transformation. Materials like chalk, clay, and limestone are first crushed and milled before heating in furnaces, pre-heaters, and coolers to produce clinker. The clinker is then ground, mixed with gypsum, and packed.

Grinding and crushing are energy-intensive processes, with clinker grinding accounting for 38 % of total electricity use and raw material crushing for 33 %. Other energy consumers include air blowers, fuel delivery, and motors in kilns.

Energy-saving measures during grinding are crucial for sustainable cement production. MCDM methods help evaluate and prioritize these energy-saving options effectively. The study used the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), VIekriterijumsko KOmpromisno Rangiranje (VIKOR), ÉLimination Et Choix Traduisant la REalité (ELECTRE), and the Weighted Sum Model (WSM) to rank various energy efficiency alternatives.

Methods

The researchers evaluated six grinding technologies to enhance energy efficiency in the cement sector: improved grinding media (IGM), high-pressure roller press (HPRP), vertical roller mills (VRMs), high-efficiency classifiers (HECs), horizontal roller mills (HRMs), and process control and management in grinding mills (PCMG).

These alternatives were assessed across multiple dimensions of energy consumption, including energy/fuel savings, electricity savings, cost, emissions reduction, and payback period. An additional scenario considered equal weighting of all these factors.

The entropy and MCDM methods were used to rank energy efficiency options to reduce greenhouse gas emissions. Shannon's entropy determined the relative importance of each evaluation criterion, helping to reduce decision-making bias by deriving objective weights from real data.

Subsequently, four MCDM methods were used to rank the energy efficiency alternatives comprehensively. The combination of WSM, TOPSIS, VIKOR, and ELECTRE enhanced the study's credibility and replicability. The researchers then developed guidelines to promote sustainable cement production and net-zero emissions.

A sensitivity analysis was also conducted to test the robustness of the MCDM methods under different conditions, demonstrating their flexibility and consistency even when criteria weights were varied.

Results and Discussion

Applying Shannon's entropy to the initial data for energy savings in finish grinding revealed that electricity savings (kWh/ton) were the most important factors for the cement industry, followed by emissions reduction (kgCO₂/ton), cost (USD/ton), payback period (years), and energy/fuel savings (GJ/ton).

Sensitivity analysis showed that varying the importance of criteria affected the rankings. The weightings of each criterion significantly influenced the decision-making process.

The MCDM methods incorporated various perspectives and assessments to arrive at an ultimate decision, with the highest-ranked alternative being considered the best. Combining Shannon's entropy with MCDM approaches resulted in a more detailed and sophisticated analysis of energy-efficient solutions.

Under the equal-weight scenario, the rankings of the alternatives were HRM > VRM > IGM > HPRP > PCMG > HEC. The HRM option also ranked highest in scenarios prioritizing energy/fuel savings, electricity savings, and payback period. Conversely, VRM was most suitable for cost and emissions reduction.

Beyond promoting sustainability using technologies like HRMs and VRMs, the authors also suggest that governments encourage the adoption of energy-efficient grinding methods through subsidies, incentives, or regulations. Collaboration between research institutions and industry associations is also recommended to share best practices and study the effectiveness of these methods.

Conclusion

Overall, the study successfully integrates entropy and MCDM methods to develop a framework that guides the cement industry toward sustainable practices and net-zero emissions. Shannon's entropy was employed to determine unbiased criteria importance, while four MCDM methods ranked energy-efficient options.

The evaluation of six scenarios highlighted the versatility of HRMs and the emission-reduction capabilities and cost-effectiveness of VRMs. This interdisciplinary approach offers valuable insights for aligning global sustainability goals with economic feasibility.

The researchers also recommend further studies to assess the impact of these alternatives on biodiversity, resource conservation, and overall ecological footprints. Additionally, scalability, lifecycle analyses, and long-term environmental benefits should be considered to fully understand sustainable approaches in the cement sector.

Journal Reference

Ahmed, M. S., Tasnim, A., & Kabir, G. (2024). From Grinding to Green Energy: Pursuit of Net-Zero Emissions in Cement Production. Engineering Proceedings, 71(1), 8. DOI: 10.3390/engproc2024076008, https://www.mdpi.com/2673-4591/76/1/8

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