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The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The calorific value is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions.
The energy content of wood pellets is approximately 4.7 – 5.2 MWh/tonne [43] [44] (~7450 BTU/lb), 14.4-20.3 MJ/kg. [45] None of these three sets of values come even close to agreeing. High-efficiency wood pellet stoves and boilers have been developed in recent years, typically offering combustion efficiencies of over 85%. [ 46 ]
The specific heat of the human body calculated from the measured values of individual tissues is 2.98 kJ · kg−1 · °C−1. This is 17% lower than the earlier wider used one based on non measured values of 3.47 kJ · kg−1· °C−1.
The wood can already be used after 6 days. [2] Its calorific value is around 4720 kcal/kg. [ 5 ] The yield is long-term high: Calliandra calothyrsus can be harvested during 10 to 20 years.
Smokeless fuels generally have a high calorific value, with that of anthracite being greater than dry wood for example, and many smokeless briquettes are made from this type of coal. Thus anthracite has a calorific value of 32.5 MJ/kg compared with that of dry wood of about 21 MJ/kg.
The calorific value Q of coal [kJ/kg] is the heat liberated by its complete combustion with oxygen. Q is a complex function of the elemental composition of the coal [citation needed]. Q can be determined experimentally using calorimeters. Dulong suggests the following approximate formula for Q when the oxygen content is less than 10%:
Lignite (derived from Latin lignum meaning 'wood'), often referred to as brown coal, [1] is a soft, brown, combustible sedimentary rock formed from naturally compressed peat.It has a carbon content around 25–35% [1] [2] and is considered the lowest rank of coal due to its relatively low heat content.
Thus methane has an HHV (Higher heating value) of 55.50 MJ/kg, the highest value of common fuels. Diesel fuel has an HHV value of 44.80 MJ/kg and anthracite coal a value of 32.50 MJ/kg. Moisture and ash-free firewood has a lower value of 21.70 MJ/kg while dry peat has the lowest value of all common fuels of about 15.00 MJ/kg.