Bio Coal as Coke Replacement: A Comprehensive Analysis



This research explores the strategic adoption of bio-coal, derived from coconut shells, as a substitute for traditional coke in the Steel manufacturing process. Focused on the reduction of carbon emissions and overall environmental impact, the study evaluates the viability of bio-coal through comprehensive trials and analyses. The bio-coal blends demonstrated comparable metallurgical properties, with promising carbon recovery rates and favourable heat characteristics. Stack emission reports indicate a no negative environmental performance during the trials

Bio coal
melting of scrap and ferro alloys

Problem Definition

Stainless steel is manufactured through melting of scrap and ferro alloys, coke serving as a primary reducing agent. The reduction of reactive metal oxides by coke at elevated temperatures produces carbon monoxide (CO) and releases the metal, effectively removing oxygen from the oxide But carbon emission of coke is very high with the emission of 3.33 kg of CO2 for every 1 kg of coke used, according to the Intergovernmental Panel on Climate Change (IPCC).

Properties of Bio-Coal for Metallurgical Processes:

The properties of bio-coal play a significant role in determining its viability as a substitute for metallurgical coke in industrial processes. This section dig into key characteristics, including calorific value, ash content, volatile matter, fixed carbon, moisture, sulfur, and their collective impact on metallurgical product quality. Through comprehensive analysis and comparison with traditional coke, this exploration aims to provide a subtle

Metallurgical processes

Characteristics Comparison Between Bio-Coal and Coke in Steel Industry

The following table shows how Bio-Coal simply outperforms coke from coal.

Chemistry Compare
CharacteristicsUOMBio CoalCoke
Moisture % 5.5 15
VM % 15.16 2.3
Ash % 2.33 16
Fixed Carbon % 82.51 81.3
GCV Kcal/Kg 7000 6800
Sulphur Content % 0.1 0.66 - 0.81

*Bio-Coal has higher calorific value comparing to regular coke from coal. Calorific value is the most important characteristics of a good fuel

Examining the data, bio-coal demonstrates a lower moisture content (5.5% vs. 15%) and significantly higher volatile matter (15.16% vs. 2.3%) compared to coke. Moreover, bio-coal exhibits lower ash content (2.33% vs. 16%) and a slightly higher fixed carbon composition (82.51% vs. 81.3%). Notably, the calorific value (GCV) of bio-coal surpasses that of coke (7000 Kcal/Kg vs. 6800 Kcal/Kg), suggesting enhanced energy potential. Furthermore, the negligible sulphur content in bio-coal (0.1%) aligns with environmental considerations.

Calorific Value

Bio-coal presents a promising alternative to traditional metallurgical coke due to its competitive calorific value. The calorific value of bio-coal, expressed in kilocalories per kilogram (KCal/kg), is a crucial parameter influencing the energy efficiency of metallurgical processes. In comparison to metallurgical coke, bio-coal exhibits 7000 Kcal/kg, indicating its potential as an energy-rich substitute which is comparable to Metallurgical Coke being used in the process with energy value of 6800 Kcal/kg.

Reactivity and Combustion Characteristics

The reactivity of bio-coal during combustion significantly impacts temperature profiles and overall combustion efficiency in metallurgical processes. The average tapping temperature during the trail was remained at around 1560 degree Celsius using bio-coal which was in accordance with the desired outcome.

High Fixed Carbon Content

The fixed carbon content in bio-coal contributes significantly to its energy content. Comparative analysis with metallurgical coke fixed carbon composition (81.3%) & Bio-Coal fixed carbon composition (82.51%) provides insights into the potential of bio-coal as an energy source in metallurgical applications. The fixed carbon content is integral to understanding the combustion efficiency and energy release during the process, carburizing effect, better Slag Foaming: protect Lining & better Reducing property.

Low Sulfur Content

Lower sulfur content translates to reduced sulfur dioxide (SO2) emissions during combustion, lower sulfur content supports improved air quality and human health. Sulfur content in bio-coal is a critical parameter with environmental implications. Comparative studies indicate Bio-Coal with sulfur content less than 0.12% of bio-coal and its potential impact on emissions. Low sulfur content aligns with sustainable and green initiatives, making bio-coal an attractive option for industries aiming to reduce their environmental impact and promote corporate social responsibility.

Low Carbon Footprint

Bio-coal is derived from biomass sources, which absorb carbon dioxide (CO2) during their growth. As a result, the combustion of bio-coal releases CO2 that was recently captured, making it a carbon-neutral or even a carbon-negative fuel source. The substitution of bio-coal for coke in metallurgical processes can directly contribute to reducing the greenhouse gas intensity of these operations..

High Level Solution

In order to replace the coke and to maintain the liquid metal chemistry, Coconut shell charcoal natural lumps identified as a replacement of coke having following charterstics.

DescriptionUOMCoconut Shell
Moisture % 5.5
VM % 15.16
Ash % 2.33
Fixed Carbon % 82.51
GCV Kcal/Kg 7000
Sulphur Content % 0.1

Trial plan was made and implemented to replace the coke as reducing agent. 5 grade were identified and trial done with Mixing of Coke and Bio coal (Coconut Shells). Comparative analysis of the trial for different grade manufacturing (Graphs / infographics) and different combination of coke: biochar ratio.

Heat DescriptionGradeCoke Used - KgBio Coal Used - KgHeat Carbon &Carbon Recovery
2308J0282 JSLUDD 122 180 2.25 97%
2308J0283 JSLUDD 227 180 1.97 87%
2308J0294 409L 759 360 1.81 68%
2308J0296 409L 680 390 1.78 57%
2308J0331 J-201 70 400 1.8 87%
2308J0332 J-201 103 400 2.0 85%
2308J0340 SUH409L 0 680 1.9 77%
2308J0341 SUH409L 120 690 1.75 76%
2308J0361 IRSM 0 640 1.82 71%
2308J0362 IRSM 50 700 1.70 55%
Average recovery 76%

Stack Emission Report

S. No.ParticularsUnitData Observed
1 Ambient Temp. °C 38
2 Stack Temp. (Avg.) °C 97
3 Velocity of Flue Gas m/sec 10.90
4 Sampling Duration Minutes 50
S. No.ParametersUnitResultsStandard LimitsProtocol UsedOK / Not OK
1 Particular Matter mg/NM3 19.37 150 IS 11255 (P-1):1985 OK

Business Benefits

Bio-coal emerges as a standout alternative to traditional biomass fuels, bringing with its higher energy content, lower moisture, and improved handling and storage features. In a departure from fossil coal, bio-coal is free from sulfur, nitrogen oxides, and mercury. Plus, its remarkably lower ash content makes for a cleaner burn, effectively reducing greenhouse gas emissions.

These advancements in fuel technology not only boost efficiency but also align with sustainability goals. The absence of harmful pollutants commonly found in coal positions bio-coal as a promising choice for a cleaner and more environmentally conscious energy future.

Some of the key benefits are mentioned for a panorama understanding of importance of shifting to such energy alternative which are Highley efficient together with low carbon emission properties.

Environmental Advantages:
  • Lower carbon footprint through reduced greenhouse gas emissions.
  • Improved environmental performance aligns with sustainability goals.
Diversification of Energy Sources:
  • Reduces dependency on conventional fossil fuels, enhancing long-term resilience.
Positive Corporate Image:
  • Appeals to consumers, investors, and stakeholders valuing sustainability.
Market Positioning:
  • Positions the company as a responsible industry leader.
  • Attracts environmentally conscious customers and investors, enhancing brand loyalty.
Regulatory Compliance and Risk Mitigation:
  • Proactive adoption of sustainable practices mitigates regulatory compliance risks.

Benefits achieved from the trial

The potential benefits of using Bio-coal as an enabler in respect of carbon abatement is highly scalable in a NetZero business scenario. Yearly consumption at the trail plant location is around 4000MT of Coke which can impact significant in CO2 reduction of more than 13000MT

Operational / handling challenges

There were no major handling challenges were overserved during or after the trial. Satisfactory for use as a replacement of conventional coke.


The research explores the feasibility of replacing coke with bio-coal in stainless steel manufacturing processes. Trials and analyses demonstrate that bio-coal, specifically from coconut shells, can serve as an effective reducing agent with comparable metallurgical properties. The business benefits encompass improved environmental performance, reduced carbon emissions, and a more sustainable approach to steel production. This study provides valuable insights into transitioning towards a cleaner and more sustainable practice for the steel industry. This could also be a key enabler in transitioning from high to low carbon economy and a successful driver to achieve NetZero ambitious path for any Industry as well as the Nation.