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Comparative Life Cycle Assessment of Natural Gas and Coal-Based Directly Reduced Iron (DRI) Production

A Case Study for India

Experience I. Nduagu, Deepak Yadav, Nishant Bhardwaj, Sabarish Elango, Tirtha Biswas, Rangan Banerjee, Srinivasan Rajagopalan
March 2022 | Industrial Sustainability & Competitiveness

Suggested citation: Experience I. Nduagu, Deepak Yadav, Nishant Bhardwaj, Sabarish Elango,Tirtha Biswas, Rangan Banerjee, Srinivasan Rajagopalan. 2022. Comparative Life Cycle Assessment of Natural Gas and Coal-Based Directly Reduced Iron (DRI) Production: A Case Study for India. Journal of Cleaner Production. 131196. https://doi.org/10.1016/j.jclepro.2022.131196

Overview

This study develops a comprehensive cradle-to-gate (raw material to iron product) life cycle assessment of three distinct technological pathways for producing directly-reduced iron (DRI) – direct coal reduction in a rotary kiln (rotary kiln DRI) process, coal gasifier and shaft furnace (coal gasifier DRI) process, and reformed natural gas (NG) and shaft furnace (NG reformer DRI) process. The study finds that the NG reformer DRI process produces significantly lower overall emissions. The life cycle greenhouse gas (GHG) emissions of the coal gasifier and the rotary kiln DRI processes are noted to be similar.

Key Highlights

  • The life cycle GHG emissions associated with DRI production range from 1391.1 to 1880.0 kgCO2e/t-DRI for the rotary kiln DRI process, 1565.5 to 1969.1 kgCO2e/t-DRI for the coal gasifier DRI process, and 815.3 to 1160.1 kgCO2e/t-DRI for the NG reformer DRI process.
  • The NG reformer DRI process has the potential to lower the life cycle greenhouse gas emissions footprint of DRI from the coal-based processes by 33-41 per cent (17-59 per cent considering sensitivities).
  • The thermal heat-related emissions from the coal gasification process is 17 per cent lower than the rotary kiln route. However, after accounting for electricity consumed in the coal gasification plant, the plant (or scope 1) emissions from rotary kiln and coal gasification process become similar.
  • The life cycle analysis shows that the rotary kiln DRI process offers 4.5-11 per cent lower GHG emissions when compared to the coal gasifier DRI process, primarily due to upstream emissions from iron ore pellets used in the coal gasification process.
  • The study results will be very beneficial to future work on hydrogen-based DRI, since the process is analogous to the NG reformer and coal gasification DRI process considered in the assessment.

Key Recommendations

  • Consider low-carbon fuels and deploy decarb-ready technologies to achieve net-zero emissions and achieve self-reliance.
  • Include life cycle GHG emissions as an important criteria for comparing various technology pathways while making decisions on greenfield investments.
It is important to follow a uniform, consistent approach using tools like life cycle assessment to quantify the GHG emissions of different fuel and technology options on a holistic cradle-to-gate basis.

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