Making steel without emitting CO2
Researchers are exploring electrolysis-based methods to make iron and steel without emitting CO₂, but current approaches produce large quantities of chlorine gas and require very pure ore, raising safety, market, and cost concerns. Commenters compare this to hydrogen-based “green steel” routes and other low-carbon materials efforts, noting trade-offs in energy demand, process complexity, and byproducts. The thread also touches on geopolitical and economic angles, such as countries outsourcing emissions by shutting domestic steel plants, and where abundant clean power (solar, hydro, nuclear) could reshape where heavy industry is located.
Scope of “CO₂-free steel”
- Several commenters note the article is about smelting, not mining; CO₂-free extraction of ore is a separate challenge.
- Mining decarbonization efforts mentioned: electric/hydrogen/ammonia-powered equipment and regenerative rail systems, with practical underground benefits like reduced heat and less need for cooling.
Chlorine Co‑production: Scale, Safety, and Usefulness
- The process generates roughly as much chlorine gas as iron (1:1 by moles, not by mass).
- Concern that global steel output (
2000 Mt) far exceeds current Cl₂ demand (100 Mt), so large-scale adoption would flood the chlorine market. - Chlorine is highly toxic; several commenters say they’d rather manage CO₂ than large new Cl₂ streams. Others argue Cl₂ is already produced industrially, is easy to capture and reactive, and has valuable uses (e.g., PVC), but overall demand is limited.
- Suggestions include neutralizing excess Cl₂ with NaOH or MgO, effectively turning it back into saltwater; this is seen as technically feasible but energetically and economically “unthrifty.”
- One subthread speculates about releasing dilute Cl₂ to scrub atmospheric methane, but acknowledges serious health and environmental risks.
Comparison to Hydrogen-Based and Other “Green Steel” Routes
- Multiple comments emphasize that direct reduction of iron ore with hydrogen is a well-developed decarbonization pathway, already being piloted at scale.
- Noted issues: high electricity demand for green H₂ production, loss of exothermic CO-based reduction heat, and need to reintroduce carbon to achieve desired steel properties (creating some CO₂ unless using biogenic carbon).
- Hydrogen leakage and its indirect global warming impact are raised as underappreciated problems.
- Other explored tech: molten oxide electrolysis, sodium-assisted processes, plasma processing of red-mud waste, and alternative low-CO₂ cements.
Energy Sources and Siting
- Debate over optimal locations: deserts with abundant solar vs siting near nuclear or hydro for steady, cheap power.
- Arguments over whether nuclear’s “waste heat” is hot enough for direct process heat vs more realistic use via electricity.
- Shipping ore to low-cost electricity hubs is seen as common practice but adds transport emissions.
Economics, Policy, and Skepticism
- Some highlight national “green steel” bets (e.g., hydrogen-based processes) and fear financial risk if cheaper electrolysis emerges.
- Others criticize apparent policy “decarbonization” that simply offshores steelmaking and its emissions.
- Several commenters question the article’s economic optimism, pointing to unresolved issues: requirement for very pure ore, chlorine disposal/market limits, and lack of detailed cost analysis.