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Lecture 29

EPS 7 Lecture Notes - Lecture 29: Rapeseed, Biofuel, Canola

Earth And Planetary Science
Course Code
David Romps

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Lecture 29
Biomass power: enough room for food and fuel?
Biomass can be burned in a power plant or in a car
Like the burning of coal, oil, and gas, burning biomass emits H20 and CO2
So, why is biofuel considered carbon neutral?
Biofuel carbon cycle: (a loop)
H2O + CO2 -(photosynthesis) with solar energy O2 + CH2O (with car) and
back to H2O + CO2
Using solar energy
Tera = T =trillion
Trillion W = TERAWATT = TW
For example, 1000 GtC = 1TtC (1,000,000,000,000 chickens)
Global energy consumption
Current 20 TW
What is the maximum potential biomass energy?
1. The area of land is 150 trillion m^2
2. Crops occupy 10% of that: 15 trillion m^2
3. TSI of 1360 W/m2 comes in at the top of the atmosphere
4. Some absorbed some reflected roughly 1000 W/m2 makes it to the surface
5. Another issue: only equatorial regions get 1000 W/m2 head on around noon
- The earth is curved- less dense
- Some areas only get sun at a tilted angle
6. There is day and night
7. Factoring in everything: about 100-200 W/m2 at the surface
8. Plants convert that solar energy into biomass energy with an efficiency of only
< 1%
9. As a result, actual solar harvesting by plants is around 0.5 W/m2
10. Of course, it takes energy to grow crops
- Let us assume that 1/3 of the energy in biomass is used to grow and
harvest the biomass.
- That leaves 2/3 of the energy to be shipped out for other uses
How much possible energy from biomass?
Cropland area: 15 trillion m2
Power per area: 0.5 W/m2
Fraction of energy for sale: 2/3
Total possible power = (15 trillion m2) x (0.5 W/m2) x (2/3) = 5 TW
- Current: 20 TW
- Maximum potential biomass: 5 TW
Two main types of biofuel being used today:
1) Biodiesel
- The U.S. makes most of its biodiesel from soybeans
- Elsewhere, biodiesel is made mostly from rapeseed
- Biodiesel is mostly made of soybean oil and rapeseed oil
- Are these familiar substances? If you cook, yes! Both ingredients of oil
- Canadian scientists Stefanson Baldur and Richard Downey bred
rapeseed to make its oil palatable
- The result: Canadian oil can ola Canola
- Rapeseed flowers and seed pods (images)
- Sample molecule of vegetable oil (soybean or rapeseed) carbon and
hydrogen, separate the chain by chopping off the backbone
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