The CO$_2$ offset potential of land used for growing energy crops as a bioethanol feedstock is ______ $\times 10^6$ g of CO$_2$ /hectare (rounded off to one decimal place).
Consider CO$_2$ footprints of 10 g and 80 g of CO$_2$ per MJ for bioethanol and petrol, respectively.
Calculating CO$_2$ Offset Potential for Bioethanol
This calculation determines the CO$_2$ offset potential per hectare by comparing the carbon footprint of producing bioethanol with the footprint of the fossil-based petrol it displaces.
Step 1: Calculate Total Energy Produced Per Hectare
First, find the total energy yield from bioethanol grown on one hectare.
- Energy Content: 21 MJ/L
- Yield: 7000 L/hectare
- Total Energy = Energy Content $\times$ Yield
- Total Energy = 21 MJ/L $\times$ 7000 L/hectare = 147000 MJ/hectare
Step 2: Calculate CO$_2$ Footprint of Bioethanol Production
Next, calculate the CO$_2$ emitted during the production of this bioethanol.
- CO$_2$ Footprint of Bioethanol: 10 g CO$_2$/MJ
- Total Bioethanol CO$_2$ Footprint = Total Energy $\times$ CO$_2$ Footprint of Bioethanol
- Total Bioethanol CO$_2$ Footprint = 147000 MJ/hectare $\times$ 10 g CO$_2$/MJ = 1470000 g CO$_2$/hectare
Step 3: Calculate CO$_2$ Footprint of Displaced Petrol
Determine the CO$_2$ emissions that would have occurred if the equivalent energy was derived from petrol.
- CO$_2$ Footprint of Petrol: 80 g CO$_2$/MJ
- Total Petrol CO$_2$ Footprint = Total Energy $\times$ CO$_2$ Footprint of Petrol
- Total Petrol CO$_2$ Footprint = 147000 MJ/hectare $\times$ 80 g CO$_2$/MJ = 11760000 g CO$_2$/hectare
Step 4: Determine Net CO$_2$ Offset Potential
The offset potential is the difference between the CO$_2$ emissions avoided (from petrol) and the CO$_2$ emitted (from bioethanol production).
- CO$_2$ Offset Potential = Total Petrol CO$_2$ Footprint - Total Bioethanol CO$_2$ Footprint
- CO$_2$ Offset Potential = 11760000 g CO$_2$/hectare - 1470000 g CO$_2$/hectare
- CO$_2$ Offset Potential = 10290000 g CO$_2$/hectare
Step 5: Format the Final Answer
Convert the result to the required format ($\text{______} \times 10^6$ g CO$_2$ / hectare) and round to one decimal place.
- 10290000 g CO$_2$/hectare = 10.29 $\times 10^6$ g CO$_2$/hectare
- Rounded to one decimal place: 10.3 $\times 10^6$ g CO$_2$/hectare
The CO$_2$ offset potential is 10.3 $\times 10^6$ g of CO$_2$ /hectare.
Important Questions from Global Warming
- Methane hydrates have special crystal structure of water, where methane gas molecules are trapped. Choose the correct option(s) from the following
- Which one of the following statements is correct regarding Global warming?
The correct ascending order of the following greenhouse gases with respect to their global warming potential relative to $CO_2$ in the time horizon of 100 years is
