AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Biogas has higher thermal efficiency compared to dung cakes. When cattle dung is burned directly, it wastes valuable manure. In contrast, biogas plants convert dung into gas for fuel and also yield improved quality manure as a by-product. Thus, biogas provides twin benefits — energy and manure — making it a more efficient use of cattle dung.
Source: Non-Conventional Sources of Energy, Chapter 5
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The key points examiners look for are:
The textbook explicitly states: "Biogas is by far the most efficient use of cattle dung. It improves the quality of manure and also prevents the loss of trees and manure due to burning." Quote or paraphrase this directly for full marks. Don't over-explain — two clear points earn both marks.