LECTURE 25 ICA 5 HUMAN USE OF SUN’S ENERGY (No pages to read in text)
I. HUMAN USE OF ENERGY AS FOOD
1.Relevant ecological concepts:
A. population size + need; carrying capacity (vs. ‘demand’ for animal food)
B. productivity of plants and animals
C. trophic level of consumption
D. ecological efficiency (‘10%)
E. land use (landscape and conservation ecology)
2. What are challenges now and in future? From Lester Brown’s Plan B.
A. Less water for irrigation
B. Increasing temperatures  drought
C. Loss of land to nonfarm uses
D. Increased fuel costs
E. Increased costs to produce fertilizers
F. Fewer new technologies on horizon
3. Approaches to Feeding 7 Billion Well!!
1. Improve land (plant) productivity
A. increase multi-cropping
B. improve water-use efficiency
C. plant less water-demanding crops
D. move down food chain so less water used to produce animal feed
E. raise the cost of water
F. put local people in charge to manage resources
2. Produce animal protein more efficiently
A. 38% of grain is used as animal feed in world
B. variation in animal efficiency in conversion of grain to protein
beef – lowest; aquaculture of herbivorous fish highest
C. variation among countries in type of meat consumed
China consumes most – and loves pork; 2nd in world = chickens; fish on rise
D. Most soybeans used as grain for animal food; has improved efficiency greatly
3. New animal protein production systems
A. Milk in India: feed animals with roughage (corn stalks; straw; grass)
B. Use crop residues (straw and corn stalks) as feed for cattle
C. China: aquaculture - 4 fish feeding at different trophic levels
4. Move down food chain: Why does human population size depend on our trophic level?
A. How many people can the earth support? Depends at what trophic level,,,
1. US consumes 800 kg grain/ person/yr – at this level support 2.5 billion
2. Italy
400
5
3. India
200 (almost all directly to humans)
10
B. Of our 800 kg grain, 100 kg is eaten as grain directly; 700 goes to feed animals
C. Complete this table to understand the concept of eating lower on the food chain:
DIET of
2000 calories
Calorie Source
# Calories
Consumed
1. 100% Plant Plant
2000
0% Animal Animal
XXXX
2. 90% Plant
Plant
1800
10% Animal Animal
200
3. 70% Plant
Plant
1400
30% Animal Animal
600
4. 50% Plant
Plant
1000
50% Animal Animal
1000
5. 0% Plant
Plant
XXXX
100% Animal Animal
2000
* Assume 10% Ecological Efficiency
Ecologically
Equivalent
Calories*
2000
XXXX
1800
2000
1400
6000
1000
10000
XXXX
20000
Total
Ecologically
Equivalent
Calories
2000
XXXX
XXXX
3800
XXXX
7400
XXXX
11000
XXXX
20000
5. The Hungry Planet (Peter Menzel and Faith D’Aluisio)
Item
Range
USA
$ spent on food
$1 to $500 /week
calories in diet
2114 (Darfur) to
3774 (28% from animal products)
sugar used
almost none to
158 pounds/year)
obesity levels
1% (China/Japan)
27%
meat consumption
7 in Bhutan
275 pounds/year
6. Calculate your daily required calories:
Height (in) ____________ Activity level ____________ BMI _______________
Weight (lb) ____________ Calories if 30 yr _______ Calories for my age_____
7. Assignment: bring to class on Thursday:
A. Keep track of everything you eat for 24 hr.
B. Use: U of I’s Nutrition Analysis Tool 2.0: http:www.nat.illinois.edu/mainnat.html
C. Figure out and write on piece of paper (show steps 1-3 below):
1) calories consumed from plants; from animals; total calories
2) % of total calories from animal sources
3) calculate amount of ecologically equivalent calories consumed relative to a vegetarian
e.g. total calories = 2100; plant calories = 1449 = ecological equivalent plant calories
animal calories = 651; (651 x 10) = 6510 = ecological equivalent animal calories
total ecologically equivalent calories = 7959
My diet/vegetarian diet = 7959/2100 = 3.8 X more ecologically equivalent calories
than vegetarian
II. HUMAN USE OF ENERGY FOR FUEL
1. Relevant ecological topics:
A. Sun: origin of (almost) all energy that humans use
B. Ecosystem = energy-transforming machine
C. Primary Production sets limits on energy fixed by biosphere
D. Photosynthesis: sun energy transferred to chemical bond energy
E. Respiration (or burning):
Release (and transfer) of chemical bond energy; generation of ATP + heat
Aerobic
Anaerobic: less release as energy
F. Incomplete decomposition: accumulate biomass + energy
PAST: storage of chemical bond energy
2. Scenario: Accumulation of chemical bond energy from past photosynthesis
A. Production > consumption
B. Death, then decomposer food chain
C. Bury by sediments – decomposition slowed and incomplete
D. Biomass accumulates
E. Organic matter transformed to ‘fossil’ fuels
3. What physical transformations of organic matter led to fossilized biomass?
When: Carboniferous = Devonian, Mississippian, Pennsylvanian 3-4 million yrs ago!
Where: Ocean
What happened: Algae (diatoms)
sedimentation  decomposition by bacteria/protists  pressure/heat 
(Crude) oil + natural gas (hydrocarbons)
Where: Land
What happened:
Woody plants in swamps biogas via anaerobic respiration by bacteria
Incomplete decomposition  peat ( a fuel)
Sedimentation 
Pressure + heat transformed
wood fragments  thermogenic natural gas
leaves and wood  oil + coal
If anaerobic  S in coal
Trapped by overlying sediments
Retrieval by drilling/strip mining/digging
4. Chemical transformation of organic matter
Starting compounds: Lipids, proteins, carbos, lignin, cellulose in biomass
Kerogens (mix of complex heavy hydrocarbons)
Heat
Lighter hydrocarbons by breaking bonds of kerogens
5. PRESENT: break fossilized chemical bonds
A. What are major uses of fossil fuels?
Which fuel is used for which use?
1. heat
oil, coal, gas
2. machines
oil, gas
3. electricity
oil, coal
B. What is the relation of gasoline to oil?
gasoline is one of many products derived from distillation of oil
C. What is the relation of electricity to fossilized fuels?
use coal, oil  steam, wind  turn turbines wrapped in copper and
with magnets  strip electrons from copper  flow of electrons
6. What are your sources of electricity and their relative importance?
Put a * by each with fossilized sun’s energy.
A. coal * = 2
B. oil * = 1
C. natural gas * = 3
D. nuclear = 4
E. renewables * = 5
7. How do the various sources differ in ‘cleanliness’? (= amount of CO2/SO4 produced)
(much SO4 from some coal)
Coal: 1200 g CO2/kw/h electricity
Oil:
900
Gas: 750
Renewables: < 50
8. Development is ‘sustainable’ if it “meets the needs of the present without
compromising the ability of future generations to meet their own needs.”
How realistic is ‘intergenerational equity’, if we are rapidly exhausting resources?
Case 1: Renewable Resources
A. If annual depletion rate > annual growth rate,
then over-harvesting (forests, fisheries, wildlife) will decrease amount for future generations.
If present-day usage < annual increase in stock  enough for future generations only if
non-positive human population growth.
If population is growing, then current depletion must be <annual increase
(to allow stock to grow over time).
Holding current consumption to be < annual increase lowers well-being of present generation.
So how much will we sacrifice our standard of living for those born 100 or 1000 in future?
What is relative importantce of renewable sources of energy?
Put a * if it depends on sun’s energy.
A. 5 = *Solar  heat and electricity
B. 3 = *Wind  electricity
C. 2 = Hydropower  electricity
D. 4 = Geothermal  heat, electricity
E. 1 = *Biofuels  machines
Seed  ethanol in gasoline
Vegetable oil (from seed)  biodiesel
Crop residues (e.g. corn stalks) +
Non-crop cellulose (e.g. switch grass + Miscanthus ethanol
(see PPT on Biofuels on 203 lecture website)
Case 2: Non-renewable Resources (e.g. oil)
Speed of Depletion of Non-renewable Energy (stored 3-400 million years ago)
When were they discovered and put to use?
Coal: 1700s = Industrial Revolution
Oil  gas: 1859 in Titusville, PA
Electricity: late 1800s (Edison)
What is projected time of depletion? oil peak is now (or past in many countries)
So use up in about 300 years!
(2.5) – 3 trillion barrels recoverable oil in world today
Global mean per individual per year = 5 barrels/yr –necessarily reduces amount for future
USA “
“
“
“ “ = 25 barrels/yr
How much oil should we be using to assure ‘intergenerational equity’ for 1000 years?
Assume world population size = 10 billion (and stable)
Annual world consumption per year = 50 billion
Need how much for 1000 years
= 50 trillion (…but we have only 3 trillion left…)
At current world rate of consumption, how many years will it take to run out of oil? =
3 trillion / 50 billion = 33/5 = 60 years
At current USA rate of consumption? = 5 x faster = 12 years
To be equitable for 1000 years, we need to reduce to 3 billion /yr =
we need to reduce global per capital consumption by 94%
So…how sustainable are we? Are we deceiving ourselves?