Question

Products P and Q have life cycle phases of material extraction, production, use, and end of life disposal. CH$_4$, CO$_2$ emissions and mass used per functional unit (f.u.) from the different phases of the products are given in the following tables. Product P \[ \begin{array}{|c|c|c|c|} \hline \text{Phase} & \text{CO$_2$ emissions (kg/tonne)} & \text{CH$_4$ emissions (kg/tonne)} & \text{Mass (tonne/f.u.)} \\ \hline \text{Material Extraction} & 1.0 & 0.75 & 4.0 \\ \text{Production} & 1.5 & 1.0 & 2.0 \\ \text{Use} & 0.5 & 0.0 & 1.0 \\ \text{End of life disposal} & 1.0 & 0.25 & 1.0 \\ \hline \end{array} \] Product Q \[ \begin{array}{|c|c|c|c|} \hline \text{Phase} & \text{CO$_2$ emissions (kg/tonne)} & \text{CH$_4$ emissions (kg/tonne)} & \text{Mass (tonne/f.u.)} \\ \hline \text{Material Extraction} & 0.75 & 0.75 & 3.0 \\ \text{Production} & 0.25 & 1.0 & 2.5 \\ \text{Use} & 0.0 & 0.5 & 0.75 \\ \text{End of life disposal} & 2.0 & 0.0 & 0.75 \\ \hline \end{array} \] Given: Global warming potential (GWP) of CH$_4$ = 23 kg CO$_2$ equivalent per kg of CH$_4$.

• A. Greenhouse gas emissions (kg CO$_2$ equivalent/f.u.) from the ‘Material extraction’ phase of product P is higher than that of product Q.
• B. Greenhouse gas emissions (kg CO$_2$ equivalent/f.u.) from the ‘Production phase’ of product Q is higher than that of product P.
• C. Greenhouse gas emissions (kg CO$_2$ equivalent/f.u.) from the ‘End of life disposal’ is higher for product Q than that of product P.
• D. Greenhouse gas emissions (kg CO$_2$ equivalent/f.u.) from the ‘complete life cycle’ of the product P is higher than that of product Q.

Hint:

- Always multiply emission factors with mass per functional unit.
- Convert CH$_4$ to CO$_2$ equivalent using GWP (23).
- Compare phase-wise values carefully.

Answer 1

The Correct Option is A, B, D

Step 1: Formula.
For each phase, \[ \text{GHG emissions (kg CO$_2$ eq/f.u.)} = \big(\text{CO$_2$ emissions} + 23 \times \text{CH$_4$ emissions}\big) \times \text{Mass (tonne/f.u.)} \]
Step 2: Product P calculations.
- Material Extraction: $(1.0 + 23 \times 0.75)\times 4 = (1.0+17.25)\times 4 = 18.25 \times 4 = 73.0$
- Production: $(1.5 + 23 \times 1.0)\times 2 = (1.5+23)\times 2 = 24.5 \times 2 = 49.0$
- Use: $(0.5+0)\times 1 = 0.5$
- End of Life: $(1.0 + 23 \times 0.25)\times 1 = (1.0+5.75)\times 1 = 6.75$
\[ \text{Total P} = 73.0 + 49.0 + 0.5 + 6.75 = 129.25 \, \text{kg CO$_2$ eq/f.u.} \]
Step 3: Product Q calculations.
- Material Extraction: $(0.75+23\times 0.75)\times 3 = (0.75+17.25)\times 3 = 18.0 \times 3 = 54.0$
- Production: $(0.25+23\times 1.0)\times 2.5 = (0.25+23)\times 2.5 = 23.25 \times 2.5 = 58.125$
- Use: $(0+23\times 0.5)\times 0.75 = (11.5)\times 0.75 = 8.625$
- End of Life: $(2.0+0)\times 0.75 = 1.5$
\[ \text{Total Q} = 54.0 + 58.125 + 8.625 + 1.5 = 122.25 \, \text{kg CO$_2$ eq/f.u.} \]
Step 4: Compare statements.
- (A): Material extraction → P = 73.0 vs Q = 54.0 → P is higher . - (B): Production → P = 49.0 vs Q = 58.125 → Q is higher . - (C): End of Life → P = 6.75 vs Q = 1.5 → P is higher . (So (C) is wrong). Correction: Actually Q has lower than P, so statement (C) is FALSE. - (D): Complete cycle → P = 129.25 vs Q = 122.25 → P is higher .
Step 5: Final Check.
Correct statements = (A), (B), (D). Final Answer: \[ \boxed{\text{(A), (B), (D)}} \]