[Biology Class Notes] on Calorific Value]]>

The calorific value defines the energetic content of the materials; it is the amount of heat a substance produces after complete combustion. You can express it as the gross calorific value (GCV) or high heating value. Also, the calorific value of a substance (generally, solid biofuel or food) is the specific energy of combustion for a unit mass. The SI unit of the calorific value is KJ/Kg.

Effectiveness of the Calorific Value

The effectiveness of a food fuel depends on the calorific value; the higher the value, the higher the efficiency, and vice versa. For example, Hydrogen fuel has the highest calorific value, i.e.150 KJ/Kg. Therefore, it is easy to understand that the efficiency of the substance is proportional to the calorific value. Also, water vapor that is generated in the combustion process contains heat and if it is recovered through different techniques, the substance will have a higher calorific value (GCV) and vice versa when it results in a lower or Net calorific value (NCV). NCV is the result when the products of combustion are allowed to escape.

Calorific Value Definition

“Calorific value can be defined as the amount of heat produced as a result of the complete combustion of a unit volume of the substance.” 

How to Calculate Calorific Value 

The calorific value of the fuel is the amount of heat or energy a fuel generates during complete combustion. It is the variable of the heat or energy released, which is either measured in Gross Calorific Value (GCV) or Net Calorific Value (NCV). The calorific value of a fuel can be determined using a bomb calorimeter. With the above understanding of calorific value, we can write the calorific value formula as follows:

Calorific Value Formula

Net calorific value (NCV) = Gross calorific value (GCV) – Latent heat of water vapors

OR

Gross calorific value = Net calorific value + Latent heat of water vapors

Which Fuel Has the Highest Calorific Value?

A good fuel is considered to have a higher calorific value. For example, LPG, Petrol, Kerosene, and Biogas are considered to be suitable fuels having higher to lower calorific values in descending order, with LPG having the highest calorific value. It is also fundamental for defining the commercial value of the substance and is the most important characteristic to establish the price of the solid biomass.

Calorific Value of Food

A calorific food value is calculated in terms of kilocalorie, which is defined as the amount of energy required to raise the temperature of one litre of water by 1 degree. The energy value of food represents the value as a fuel to the body. This may be less than the heat value obtained with the help of experiments where food is burnt outside the body with the help of a bomb calorimeter. It is so because some of the food’s energy may be ‘lost’ during digestion and metabolism inside the body. As food also contains fiber components, it is usually subtracted from the total carbohydrate, fat, protein, or alcohol. To determine the calorific value of various foodstuffs, a sample weight is balanced Bomb Calorimeter, which is a metallic chamber surrounded by an amount of water whose temperature is measured when the food is ignited. It is found out that by burning all these energy-containing nutrients, the average values for-

• Protein is [frac{4Kcal}{gram}]

• Carbohydrate is [frac{4Kcal}{gram}]

• Fat is [frac{9Kcal}{gm}]

• Alcohol is [frac{7Kcal}{gm}]

It is mentioned below in the form of a chart where the calorific value of food is numbered in [frac{KJ}{gm}] as well as [frac{Kcal}{gram}] . Fat is the most energy-rich macronutrient, which is then followed by alcohol, protein, and carbohydrate.

What is the Calorific Value of Fuel?

When we burn coal, petroleum, diesel, kerosene, or any flammable gas, it is capable of generating electricity in a thermal power generating plants. So, the best fuel to generate electricity depends on its quality which is determined by the calorific value of a fuel. So, the question is- ‘what is the calorific value of a fuel’? The calorific value of fuel can be defined as the amount of heat produced by the complete combustion of one unit of any fuel. The unit depends upon the type of fuel; for example, coal is a solid fuel, so it is measured in weight units, whereas we use volume units for any gaseous or liquid fuel. Therefore, the calorific value for them will be measured in Kilocalorie per Kilogram and Kilocalorie per Litre, respectively.

In the chart above, the calorific value of different fuels has been drawn where Petrol, Diesel and Heavy Oil have their calorific values in a similar range, i.e., 11,000 Kcal per Kg. However, studies have shown that Petrol has the maximum one. Anthracite coal and coal gas have 8500 kcal per kg and 76000 Kcal per cubic meters, respectively. Bituminous coal has 7600 Kcal per kg, whereas Lignite has 5000 Kcal per kg. Natural gas has 560 Kcal per cubic meter.

Significance of Calorific Value 

Since fuels and foods are parts and parcels of our lives that we use at every hour and second of time, it is essential to keep track of the amount of energy we consume or transport. Having a knowledge of the calorific value of fuels and food, helps us to undertake easy calculations that the gas suppliers and shippers will need to bill gas consumers. Also, it helps in determining the transportation charges; on the other hand, calorific value calculation of food will help in guiding people about a balanced calorie or food consumption to remain healthy. Food with too little or too high calorific value may lead to health problems, so it should be kept in mind that the body will be able to carry out daily activities and will remain fit if calories are consumed in a specific range. The calorific value of the fuels helps you in deciding which fuel is a good fuel. This is done by comparing different calorific values of the different fuels. Fuel with the highest calorific value is the best fuel.