Moisture content, calorific value, ash percentage — the spec differences that separate premium briquettes from cheap, damaging alternatives.
The Kenyan biomass briquette market has grown rapidly over the past five years, and with that growth has come significant variation in product quality. Walk into any industrial fuel market in Nairobi, Mombasa, or Nakuru and you will find briquettes priced anywhere from KES 8,000 to KES 16,000 per tonne — a range that reflects not competitive pricing but genuine differences in calorific value, moisture content, ash percentage, and mechanical durability. Choosing briquettes based on price per tonne rather than cost per unit of energy delivered is one of the most expensive mistakes a Kenyan manufacturer can make. This guide explains what the specifications actually mean and how to evaluate them before signing a supply agreement.
The Three Specifications That Matter Most
Net calorific value, measured in kilocalories per kilogramme, is the most important single specification. Premium briquettes from quality-controlled manufacturers deliver 4,200 to 4,800 kcal/kg on an as-received basis. Cheap briquettes made from poorly sorted or contaminated feedstocks often deliver only 3,200 to 3,600 kcal/kg. The difference is not marginal — a briquette delivering 3,400 kcal/kg requires 24 percent more tonnage to produce the same amount of steam as a 4,600 kcal/kg briquette. At scale, this difference eliminates any apparent price advantage of the cheaper product and typically results in a significantly higher actual cost per tonne of steam produced.
Moisture content is the second critical specification. Briquettes with moisture content above 15 percent on an as-received basis waste a significant fraction of their combustion energy evaporating water before any useful heat is released. Every percentage point of moisture above 15 percent reduces the effective calorific value by approximately 50 kcal/kg and increases combustion time, reducing boiler throughput. High-moisture briquettes also cause incomplete combustion, producing excess carbon monoxide and particulate emissions. Premium briquettes should be supplied at 10 to 14 percent moisture content with covered storage maintained throughout the supply chain. Ash content is the third key parameter: ash above 5 percent by weight increases grate cleaning frequency, reduces combustion efficiency, and in severe cases can cause clinker formation that damages combustion grates.
How to Test Before You Commit
The most reliable way to verify briquette quality is a proximate analysis from an accredited laboratory. A proximate analysis measures moisture, volatile matter, fixed carbon, and ash content — from which calorific value can be calculated. Request a proximate analysis certificate from any supplier before signing a contract, and specify in the contract that each delivery must be accompanied by a certificate for that specific batch. For ongoing supply relationships, we recommend independent sampling and testing of one delivery in every five. A field test you can do on site is the burn test: weigh a known quantity of briquettes, combust them under controlled conditions, and weigh the ash residue. Ash mass divided by starting mass gives you the ash percentage, which is a quick proxy for overall quality.
Cost per gigajoule delivered is the correct unit of comparison between competing briquette suppliers — not cost per tonne. To calculate it, divide the price per tonne by the net calorific value in gigajoules per tonne (1 GJ = 238,846 kcal). A briquette costing KES 12,000 per tonne with a calorific value of 4,500 kcal/kg costs KES 2.81 per gigajoule. A briquette costing KES 9,500 per tonne with a calorific value of 3,200 kcal/kg costs KES 3.12 per gigajoule — 11 percent more expensive per unit of energy despite being 21 percent cheaper per tonne. Lean Energy Solutions supplies Lean Briqs with a calorific value of 3,800 to 4,200 kcal/kg, low ash content of 6 to 8 percent (usable as fertilizer), and zero sulphur — compressed mechanically with no binders added, backed by quality control on every delivery.
David Mwangi
Energy Specialist, Lean Energy Solutions Kenya
