A supplier sends you a wood fuel sample. The report says 19 MJ/kg . Looks good. Then the first truck arrives at the plant, and the wood is much wetter than the sample. The furnace is running, but the heat output is not what you expected. Fuel consumption goes up. The operator adjusts the firing rate. A few hours later, another load arrives, and the behaviour changes again. This is the part of wood fuel that is often missed. The calorific value printed on a report is important. But on its own, it does not tell you how the fuel will behave in your furnace. Moisture matters. A lot. And once you start looking at wood from that angle, the whole subject of calorific value becomes much easier to understand. So, what is the calorific value of wood? In simple terms, calorific value tells us how much heat a fuel can release when it burns completely. For wood, the figure is commonly given in MJ/kg or kcal/kg . Dry wood generally falls somewhere around 18.5 to 21 MJ/kg , depending on the species...