A lab report is the only document that tells you what is actually inside a lot of white coal. A price list and a brochure describe what a supplier hopes to deliver; the report describes what a sample of a specific batch measured on a specific day. Reading it properly takes ten minutes and can save weeks of boiler trouble.
Start With the Header, Not the Numbers
Before looking at any result, check what the report is about. A useful report names the product (for example, 90mm biomass briquette), the feedstock, the batch or lot number, the date of sampling, the date of testing, the laboratory and the test method used for each parameter. If the batch number is missing, you cannot connect the report to the fuel in your yard, and the numbers become a general advertisement rather than evidence.
Also note who drew the sample. A sample taken by the supplier and tested elsewhere is not the same as a sample drawn jointly or by an independent party. Neither is wrong, but you should know which one you are reading.
The Core Parameters at a Glance
Four lines carry most of the weight. The table below shows Bharat Bio Industries' own specification for briquettes and what each line means for your boiler. These are our specification figures, confirmed by the batch lab report, which is available on request.
| Parameter | BBI specification | What it tells a boiler operator |
|---|---|---|
| GCV | 3800 to 4200 Kcal/kg | Heat released per kg, which sets how many kg you burn per unit of steam |
| Moisture | Below 10% | Water you pay for and must evaporate before the fuel gives useful heat |
| Ash | Below 10%, typically 2 to 8% by feedstock | Non-burning residue: affects grate cleaning, ash handling and disposal |
| Sulphur | Below 0.1% | Relevant to flue gas chemistry and corrosion, and to stack monitoring |
GCV and NCV: Which Number Counts?
Gross calorific value (GCV) is the total heat released when the fuel burns and the water vapour produced is allowed to condense. Net calorific value (NCV) subtracts the heat that leaves with that water vapour, which a boiler stack does not recover. NCV is therefore always lower than GCV, and the gap grows with moisture and hydrogen content.
Indian suppliers and buyers usually quote GCV, so compare GCV with GCV. If one supplier quotes NCV and another GCV, the numbers cannot be placed side by side. Our guide on what GCV means for biomass fuel goes deeper, and the boiler side is covered in how to calculate boiler efficiency.
As-Received Versus Dry Basis
This is the most common source of confusion. Results can be reported on three bases:
- As received: the fuel as it arrived, including its moisture. This is the basis closest to what your boiler burns.
- Air dried: after partial drying in the lab, used for some standard tests.
- Dry basis: with all moisture removed. Numbers look better because the water has been taken out of the arithmetic.
A dry-basis GCV will always be higher than the as-received GCV of the same sample, and a dry-basis ash figure will be higher too. A report that quotes a fine GCV on a dry basis while showing moisture separately is not dishonest, but you must convert before comparing. If the basis is not stated at all, ask. For procurement decisions, the as-received basis is the one to hold the supplier to.
Moisture: The Quiet Cost
Moisture lowers the usable heat of every kilogram. The boiler has to evaporate that water first, and the heat for doing so comes from the fuel itself. Wet briquettes also ignite poorly, burn unevenly and can swell or crumble in storage. Moisture is also the parameter that changes after the report is issued: a lot tested dry at the plant can pick up water from a leaking truck or an open yard. That is why a delivered lot should be checked again, as described below.
Ash: Look at the Number and the Behaviour
Ash is the mineral residue left after burning. Lower ash means less fuel mass that carries no heat, less residue to clean from the grate and less to dispose of. For comparison, Indian coal ash is generally in the range of 25 to 45 percent, according to the Ministry of Coal, so a briquette in the 2 to 8 percent range changes ash handling considerably.
A single ash percentage does not tell the whole story. Ash from different feedstocks (groundnut shell, mustard stalk, sawdust) can behave differently in the furnace. Ask which feedstock the report covers, and whether the feedstock mix stays the same across batches.
Sulphur: Read It Calmly
Our briquettes are specified at below 0.1 percent sulphur. It is a useful figure to see on a report because sulphur affects flue gas composition and corrosion in cold-end surfaces. It should not be treated as the deciding factor, however: Indian coal is also officially described as low in sulphur, so do not assume a biomass fuel wins on this line. Your stack test, not the fuel label, decides what your regulator sees.
Size, Density and Durability
Many reports stop at the four chemical lines, but physical quality matters just as much to the feeder. If the report or the supplier datasheet includes it, check the briquette diameter (90mm in our case), the bulk density and a durability or breakage measure. Poor durability produces fines in transport and at the hopper, and fines mean wasted fuel and blocked feeders. Our article on pellet durability testing explains how durability is measured. Where a report has no physical data, request it or inspect the lot by hand.
Sampling Method: How the Sample Was Taken
A perfect test on a poor sample is a perfect answer to the wrong question. Good practice means taking several increments from different points of the lot, combining and reducing them to a representative sample, sealing it, labelling it with the batch number and sending it to the laboratory in a moisture-proof container. A single handful picked from the best pile is not representative. Ask the supplier how samples are drawn, how often they are tested (every batch, or once per season) and whether retained samples are kept for disputes.
Red Flags in a Lab Report
- No batch or lot number, or a report dated long before your delivery.
- The test basis is not stated, or GCV is on a dry basis while ash and moisture are not.
- The laboratory name, method or sample date is missing.
- Every parameter sits at exactly the specification limit, with no natural variation.
- The report is a photocopy or an image with no way to confirm it with the laboratory.
- The report covers a different product (for example pellets) from the one you are buying.
How to Compare Two Suppliers' Reports
Put the reports next to each other and convert them to the same footing before looking at price. Check that both use the same basis, then compare GCV, moisture and ash on that basis. Next, convert price into cost per million Kcal: divide 1,000,000 by the as-received GCV to get kilograms per million Kcal, then multiply by the delivered price per kg. A cheaper briquette with a lower GCV and higher moisture can end up costing more per unit of heat. You can run the numbers on your own plant data with our fuel cost calculator. For the wider supplier checklist, see how to choose a white coal supplier, and for how specification limits are framed in India, see biomass quality standards in India. Note that BIS standards exist for briquettes and pellets from agro residues, but BIS marking is voluntary, and Bharat Bio Industries does not claim BIS, ISO or NABL certification; we state our own specification and support it with a batch report.
How to Check a Delivered Lot Against the Report
The report describes the batch as it left the plant; your job is to confirm the truck matches. A practical routine looks like this:
- Match the batch number on the delivery documents with the number on the report.
- Inspect the load for visible moisture, mould, dust and broken pieces.
- Draw a sample at unloading from several points, seal it, and label it with the date, truck and batch.
- Send it to an independent laboratory, or run a quick moisture check on site if you have the equipment.
- Compare the result with the report and the contract limits, allowing for normal test variation.
- Keep a retained sample until the lot is consumed, in case of a dispute.
Agree these steps, and the tolerance for each parameter, in the contract before the first order, not after a disagreement. A 25 MT trial lot is a sensible place to test the whole routine. More detail on our fuel is on the biomass briquettes page.
If you would like the latest batch report and a specification sheet for your boiler, contact our team and share your fuel requirement.
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