Gross Energy Content of Methane

Correct Answer: 13.34 Kcal/g

The gross energy (GE) or heat of combustion of methane (CH₄) is 13.34 Kcal/g. This is the highest gross energy per gram among common gases produced in fermentation.

Comparison of GE Values of Common Nutrients

• Fat: 9.4 kcal/g
• Protein: 5.65 kcal/g
• Carbohydrate: 4.15 kcal/g
• Methane: 13.34 kcal/g

Despite its very high energy content per gram, methane is a complete loss because ruminants cannot absorb or utilise it metabolically — it is eructated (belched) into the atmosphere.

Environmental Significance

Enteric methane from ruminants is a significant greenhouse gas. Each adult cow produces approximately 250–500 litres of methane per day.