Calorific Value

Nov 03, 2022, 16:45 IST

A calorific value is the amount of heat energy that present in a food or fuel that is decided by the complete combustion of the specified amount at constant pressure and under normal conditions. It is also called calorific value. The unit of calorific value is kilojoules per kilogram, i.e., KJ/kg.

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

The efficiency of food or fuel usually depends on the calorific value. If the value is high, then its efficiency will be high. If the value is low, its effectiveness will decrease. A calorific value is directly proportional to its efficiency.


It refers to the amount of heat produced by the unit volume of a substance by complete combustion.

Calorific Value of Fuel

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

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

A detailed list of foods and their calorific values

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

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

Category of food Quantity(Grams) Calorific value (Approximately)
Kilojoules(KJ) Kilocalories(Kcal)
Dietary fibre 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 its compared to protein, carbohydrates, roughage, alcohols, and other biomolecules that is involved in the maintenance and metabolic processes.

Importance of Calorific Value

To carry out our daily activities, it is very important to know the calorific value of the fuel. This knowledge helps us determine the amount of energy we transport. Gas shippers and suppliers require this information to bill gas consumers. It also helps to determine the transport charges of transporters and gas suppliers.

The human body needs calories to perform daily activities. Without calories, the body would stop working, and the cells in the body would die. But if people only consumed a certain amount of calories daily, they would lead a healthy life. Eating too many or too few calories eventually leads to health problems.

Frequently Asked Question (FAQs)

Q1. What happens if a calorific value is high?

Ans. If the value is high, then its efficiency will also be high. If the value is low, then its efficiency will be low. A calorific value is directly proportional to its efficiency.

Q2. Which has highest calorific value?

Ans. LPG has the highest calorific value.

Q3. Can calorific value negative?

Ans. A negative value indicates that the combustion is exothermic so galvanic sludge can be considered as fuel due to this relatively high value.

Q4. What is the SI unit of calorific value?

Ans. The SI unit of calorific value is J/kg since calorific value is heat produced when 1 kg of fuel is burnt.

Q5. Why high calorific value is good for fuel?

Ans. When the calorific value of a fuel is high, more amount of heat energy is produced, and hence, more is its efficiency Q.

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