How is Tata Steel using biomass to cut emissions from ferro chrome production? BigMint explores

• Emissions intensity of ferroalloys sector twice that of steel
  
  
• Tata Steel breaking new ground with biomass usage in FeCr production
  
  
• Steel major has cut 11% of direct emissions through biomass-based reductant
  
  

Morning Brief: The pressing need to reduce the environmental footprint of the domestic steel industry is integrally aligned with the low-carbon transition of other sectors that provide the raw material inputs to the industry such as the mining and ferroalloys sectors.

In India, the steel industry accounts for around 25-29% of the country's total manufacturing emissions whereas the ferroalloys sector accounts for only over 0.65% of total emissions. However, the GHG emissions intensity of the domestic ferroalloys sector is higher-close to double that of the steel sector.

The overall contribution of the ferroalloys industry is meagre in comparison with the steel industry despite higher emissions intensity due to far lower production volumes of ferroalloys vis-a-vis steel. As per BigMint data, while India's steel production hovers around 145 million tonnes (mnt), production of the three main bulk alloys stood at around 4.5 mnt in FY'24.

Emissions intensity of ferroalloys

As per sources in Tata Steel's Ferro Alloys & Minerals Division (FAMD), the direct emissions intensity of ferro chrome production is 1.6 tCO2e/tlm (per tonne of liquid metal). Direct emissions from the production of ferro manganese stands at 1.3 tCO2e/tlm, while ferro silico manganese has a direct emissions intensity of 1.7 tCO2e/tlm. Ferro silicon, however, has a higher emissions intensity of around 3 tCO2e/tlm.

Notably, the production of ferroalloys is highly power intensive, with electricity consumption typically accounting for over 40% of the production costs of bulk alloys. The power consumption for 1 tonne of ferro chrome is 3.5 Mw/t (megawatts per tonne) and that of ferro manganese 2.7 Mw/t. Silico manganese production, depending on the grade, consumes in the range of 3.5-4.5 Mw/t, while 1 tonne of ferro silicon production requires around 7-8 Mw/t.

In India, the high grid emission factor due to disproportionately high share of thermal power, accounts for high indirect emissions from ferroalloys production. Over and above direct emissions from the smelting process, indirect emissions from consumption of thermal power adds to total emissions from the production process. Emissions intensity of the domestic industry typically ranges between 3.5-4.5 tCO2e/t.

Notably, this excludes upstream emissions from mining and transportation of raw materials.

Tata Steel's endeavour

Tata Steel is trialling the use of biomass to partially replace fossil fuels in ferroalloys production. Explaining the virtues of biomass, a source in Tata Steel said, "Biomass is CO2 neutral and generates less slag as compared to coal. It has higher reactivity due to its porous structure and improves electrical resistance and better electrode penetration thereby reducing electricity losses."

The choice of biomass as a reductant from the different varieties available depends on its fixed carbon content, volatile matter and ash content. "Wood charcoal due to its relatively high fixed carbon content and lower volatile matter is ideal for partial replacement of fossil fuels in ferroalloys production compared with wood or vegetable wastes as higher volatile matter in the reductant is a huge problem for smooth operations of a submerged furnace," the Tata Steel official said.

It is vital to control the phosphorous level of biomass-based reductants such as wood charcoal for stringent requirements of ferroalloys production. Tata Steel's effort to use biomass-based derivatives for ferro chrome production is a novel endeavour and the material is sourced from Rajasthan.

The company has, so far, been able to reduce about 15% of its fossil fuel use in ferro chrome production through use of biomass, which roughly equates to around 130 kgCO2 per tonne of metal produced, which is nearly 11% of direct emissions.

Planning for the future

Tata Steel is currently engaged in advancing the technology to increase the fixed carbon content of the biomass-based reductant and reduce its volatile matter for efficient integration into existing assets and production processes.

Another vital effort relates to acquiring efficiency in in-house charcoal manufacturing in order to reduce costs and emissions associated with long distance transportation of raw materials.

India's Carbon Credit Trading Scheme (CCTS) will come into effect shortly and in a world where carbon border taxes become the norm rather than exception, Tata Steel is planning for the future through technological innovations to reduce the environmental impact of ferroalloys production.