For the Indian solid-brick planning case used in this article, coal is the clear direct-cost winner. With coal at ₹8,000–₹9,000 per tonne and 5,000–5,500 kcal/kg GCV, the fixed 1.9 MJ/kg tunnel-kiln basis gives about ₹1.98–₹2.45 lakh to fire 1 lakh solid bricks. The midpoint is approximately 25.9 tonnes of coal and ₹2.21 lakh, or ₹2.21 per fired brick, before coal handling, emission control, finance and reject losses.

1. Engineering Basis: Compare Heat, Not Only Fuel Weight

A client cannot compare coal, gas and biomass only by asking, “What is the price per kilogram?” One kilogram of each fuel contains a different amount of heat. PNG is sold by standard cubic metre, LNG is commonly priced by mass or energy, and coal quality changes with GCV, moisture, ash and volatile matter.

This article therefore converts every fuel into the same required thermal-energy basis.

Why the main model uses 1.9 MJ/kg

The published tunnel-kiln project guideline used in this article reports different benchmarks for different products. It shows approximately 1.3 MJ/kg total energy for hollow blocks and about 2.0 MJ/kg total energy for solid bricks; its example for solid-brick or paver firing, including heat supplied to drying, is approximately 1.9 MJ/kg. Because Indian investors commonly ask about solid red bricks, 1.9 MJ/kg is the safer main budget basis. An efficient perforated or hollow product can be materially lower.

Why actual brick weight can change the answer

At the same kiln efficiency, a 3.5 kg solid brick requires about 40% more firing energy per piece than a 2.5 kg brick. Hollow or perforated products can therefore show a lower cost per piece even when the cost per tonne of fired product is similar. For feasibility, weigh representative dried and fired bricks—do not depend only on nominal dimensions.

Fixed assumptions: 1.9 MJ/kg SEC, coal GCV 5,250 kcal/kg and delivered coal price ₹8,500/tonne.

2. Coal vs PNG vs LNG vs Biomass: Cost for 1 Lakh Bricks

The following is an equal-energy comparison. It uses the same 570 GJ fuel input for every option so that the price and calorific-value effect is visible. A final kiln design may use different energy with different products, burners, fuels, moisture conditions and operating control.

Excluded: electricity, milling, conveying, storage loss, labour, ash disposal, emission-control OPEX, gas demand charges, minimum offtake, LNG storage/vaporization, maintenance, finance, startup/shutdown fuel and rejects.

3. Indian Coal: Realistic Cost Range at ₹8,000–₹9,000/Tonne

The midpoint alone is not enough for project finance. The first sensitivity below holds solid-brick SEC at 1.9 MJ/kg and changes the two coal variables supplied for this analysis: delivered price and GCV. A low-quality or wet coal shipment can erase the apparent saving from a lower invoice price.

This is why a purchase contract should not specify only “coal at ₹X per tonne.” It should define the agreed GCV basis, moisture, ash, sulphur, volatile matter, particle-size distribution, sampling method, laboratory method, rejection limits and price adjustment for off-spec material.

Coal quality checks before final machinery selection

• GCV/NCV: determines fuel quantity and true energy price.
• Total moisture: water must be heated and evaporated before the fuel can heat the bricks.
• Ash percentage and chemistry: affects handling, deposits, product contamination and flue-gas equipment.
• Volatile matter: influences ignition and the combustion zone.
• Sulphur: affects emissions, corrosion risk and environmental-control design.
• Particle size and grindability: must match the crusher, mill, screen, feeder and firing method.

4. The Most Useful Comparison: Rupees per Gigajoule

Delivered energy cost separates the fuel-price issue from the kiln issue. Under the midpoint assumptions, coal costs about ₹387/GJ. Biomass is about ₹598/GJ, LNG about ₹1,195/GJ, and PNG about ₹1,593/GJ.

Gas can offer better modulation, faster response and cleaner onsite handling, but “more controllable” does not automatically mean “lower cost.” At the sample prices, PNG purchased energy is more than four times the coal energy price. A reasonable improvement in gas firing control cannot, by itself, close such a large gap for ordinary common bricks.

5. Technical and Commercial Assessment of Each Fuel

Capital equipment that must be included

6. What Price Would PNG, LNG or Biomass Need to Match Coal?

Break-even pricing gives investors a fast screening rule. At coal ₹8.50/kg and 5,250 kcal/kg GCV, the competing fuel must deliver one unit of heat at approximately the same cost as coal.

These thresholds compare direct fuel energy only. If coal adds substantial handling, compliance, quality-loss or downtime cost, that verified difference may be added to the allowable competing-fuel price.

7. Calculate Cost per Saleable A-Grade Brick

A low fuel bill can hide poor production. The correct commercial denominator is the number of saleable bricks, not only the pieces loaded into the kiln. Overfiring, underfiring, black core, cracks, warping and colour variation all raise the effective fuel cost of good output.

The table below deliberately gives cleaner fuels a higher illustrative A-grade yield. It demonstrates whether the quality benefit alone is large enough to reverse the cost ranking.

The yields are a sensitivity example—not expected plant guarantees. Even with the favourable gas-yield assumption, gas does not become the lowest fuel cost at the sample prices.

8. Annual Fuel Budget for 50K, 100K and 200K Bricks per Day

Small per-brick differences become major annual cash-flow differences. The following table uses 330 operating days and the same midpoint assumptions.

These are not total manufacturing costs. They exclude clay, electricity, diesel, labour, maintenance, packing, administration, tax, finance and sales expenses. They are designed to isolate the fuel decision.

9. The Cheapest Fuel Is Only Half the Strategy

An inefficient coal kiln can waste more money than a well-operated coal kiln saves. The project should therefore optimize both fuel price and specific thermal energy consumption.

What a 10% SEC reduction is worth

At 1 lakh bricks/day and 330 days/year, a 10% reduction in purchased thermal energy saves approximately:

High-return kiln and dryer measures

• Dry bricks correctly before firing: uncontrolled residual moisture wastes firing-zone heat and increases cracking risk.
• Recover cooling-zone heat: transfer useful hot air to the tunnel dryer instead of exhausting it.
• Seal kiln cars and pressure zones: false-air leakage disturbs temperature, oxygen and draft.
• Balance airflow: fan selection, dampers and VFD control must match the actual pressure network.
• Control the firing curve: use sufficient temperature measurement, pressure indication and disciplined car movement.
• Stabilize coal preparation and dosing: consistent particle size and metered distribution prevent local over- and underfiring.
• Optimize setting pattern: bricks must expose enough area for uniform gas flow without sacrificing loading density.
• Track SEC every shift: record fuel energy divided by tonnes of good fired product, not only tonnes of fuel per day.

NES designs the tunnel kiln and tunnel dryer as one connected thermal system. Fuel selection should be completed together with clay testing, dryer design, fan calculations, heat recovery, kiln-car setting, firing curve and emission-control scope.

10. Which Fuel Is Most Cost-Effective for Your New Plant?

Data required before NES can confirm your fuel budget

• Project location, state and fuel permissions
• Target daily capacity and annual operating days
• Brick dimensions, final fired weight and product mix
• Clay test report, internal fuel content and firing-temperature range
• Green-brick and dryer-outlet moisture
• Representative coal, gas, LNG or biomass laboratory certificate
• Delivered quotations including tax, freight, unloading, minimum offtake and validity
• Proposed kiln and dryer dimensions, setting pattern and car cycle
• Local emission limits, required control equipment and consent conditions

Prepared by: Next Engineering Solutions Ltd Technical Team   |   Last technical review: 10 September 2026   |   Website: www.nextesl.net