Calorific value

What is the Calorific value?

Calorific value is the amount of heat energy present in food or fuel and which is determined by the complete combustion of specified quantity at constant pressure and in normal conditions. It is also called calorific power. The unit of calorific value is kilojoule per kilogram i.e. KJ/Kg.

Water vapor is generated in the combustion process and the heat should be recovered by using certain techniques. If the heat contained in the water vapor could be recovered then it has high calorific value. If heat contained in the water vapor could not be recovered when it has low calorific value.

The efficiency of fuel or food mainly depends on the calorific value. If the value is high, its efficiency will also be high. If the value is low, its efficiency would also be low. Calorific value is directly proportional to its efficiency.

Here is the detailed list of fuels and their calorific values:

calorific value

Fuels  Calorific Value ( Approximately)
Cow Dung 8000
Wood 22000
Coal 33000
Biogas 40000
Diesel 45000
kerosene 45000
Petrol 45000
Methane 50000
LPG 55000

LPG has more calorific value when compared to diesel, petrol, and kerosene.

A detailed list of foods and their calorific values:

The calorific value of food indicates the total amount of energy, a human body could generate during its metabolism which is expressed in Kilojoules per 100  grams or 100 ml. The calorific value of food is generally expressed in kilocalories i.e. kcal.

The below table shows the type of food and its calorific value:

Category of food  Quantity (Grams )   Calorific value (Approximately)
Kilojoules(KJ) Kilocalories(Kcal)
Dietary fiber   1       8       2
Polyhydric Alcohols   1     10       2.4
Alcohols   1    29      7
Carbohydrates   1    17     4
Protein   1   17     4
Fats   1   37      9

Fats have more calorific value when compared to carbohydrates, protein, alcohols, roughage and other biomolecules involved in the maintenance and metabolic processes.

Learn more about the calorific value and other related concepts @ BYJU’S Biology

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