Objectives
•I. Human Use of Sun’s Energy for Food
• Relevant Ecological Concepts
• Challenges + Approaches to Feed 7-10 billion
• Consequences of Moving Down Food Chain
• Comparison of Diets across Earth II. Human
•II. Human Use of Sun’s Energy for Fuel
• Relevant Ecological Concepts
• Past formation of Fossil Fuels
• Present-day Use of Non-renewable Fossil
• Fuels
• Present-day Need for Renewable Fuels
Humans + Food Energy - Relates to:
• A. Population size + carrying capacity
“ need (‘demand’ for animal food
• B. Primary and secondary productivity
• C. Trophic level of consumption
• D. Ecological efficiency
• E. Land use + landscape/conservation ecology
Global variation in estimated NPP -Humans consume 40% of global NPP!!
Challenges for future:
•Less water for irrigation
•Increasing temperatures -> drought
•Loss of land to non-farm uses
•Increased fuel costs
•Increased fertilizer costs
•Fewer new technologies on horizon
•Plan B Lester D. Brown Earth Policy Institute
How to feed 7-10 billion well!1. Improve land (plant) productivity
•A. Increase multi-cropping
•B. Improve water-use efficiency +
plant less water-demanding crops
•C. Move down food chain - less water to
produce animal feed
•D. Raise cost of water
•E. Put local people in charge to manage resources
2. Produce animal protein more efficiently.
•A. 38% of grain used as animal feed in world
•B. variation in efficiency in convert grain to protein
beef = low aquaculture herb. fish = high
•C. variation among countries in type of meat eaten
China = # 1 = pork; 2nd in world = chickens;
fish on rise, too
•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
•B. Use crop residues (straw/corn stalk) for cows
•C. China aquaculture: 4 fish at different trophic
levels
Why does human population size depend onour trophic level?
Figure 2
4. Move down food chain
•A. How many people can earth support -
depends upon our trophic level
Country kg grain/person /yr billions supported
• USA
• Italy
• India (almost all to humans)
•B. Of our 800 kg grain,
• ? eaten as grain; ? to feed animals
•C. Complete table below:
Cultural Evolution of Diet
•A. Diets include carbos + protein
•B. Must have amino acid complementarity ->
can get all required AAs from plants
• e.g. L.A.: Beans + rice (corn)
• Asia: Soybeans + rice
• Middle East: Chickpeas + wheat/millet
What do all three have in common to get
a lot of N?
Government Policies Under Debate
•A. Plant corn for food or fuel?
•B. Farm bill with farm subsidies
The Hungry Planet Peter Menzel
• ItemRange
•$ spent on food
•Calories in diet
•Sugar used
•Obsesity level
•Meat consumption
•Calculate your daily required calories
•A. Height (in)
•B. Activity level
•C. BMI (body mass index)
18.5 (small boned)
24.99 (large boned)
25-29.99 = overweight
>30 = obese
(60% of US = overweight or obese)
•D. Weight (lb)
•E. Calories if 30 yr
(add 7 female or 10 male for each year below 30)
•F. Calories for my age __________
I.Human Use of Energy for Fuel:relevant ecolgoical concepts:
• Sun: origin of (almost) all energy that humans
use
•Ecosystem = energy-transforming machine
•Photosynthesis: sun energy transferred to
chemical bond energy
•Respiration: release (and transfer) of chemical
bond energy; generation of ATP + heat
• Aerobic
• Anaerobic: less release of energy
•Incomplete decomposition: accumulate biomass
and energy
PAST SCENARIO:Accumulation of chemical bondenergy from past photosynthesis
•A. Production > Decomposition
•B. Death, then into decomposer food web
•C. Bury by sediments; anaerobic -->
decomposition slowed and incomplete
•D. Organic matter (biomass) transformed
to fossil fuels
Chemical Fossil Fuels from GeologicComposting!
Physical Transformation of OrganicMatter
•When? Carboniferous - 3-400,000,000 yrs ago
•Where?
•Ocean:
• Algae (diatoms)
• Sedimentation
• Pressure/heat
• (Crude) oil + natural gas (hydrocarbons)
Where? Land
•Woody plants in swamps
• Biogas via anaerobic respiration by bacteria
•Incomplete decomposition; much energy
remains
•Peat (a fuel)
•Sedimentation; weight squeezed out water
•Pressure + heat transformed
• wood fragments --> thermogenic natural gas
• leaves + wood --> oil + coal
• If anaerobic -- S in coal
•Trapped by overlying sediments
•Retrieval by drilling/strip mining
coal
Major coal deposits in USA -
red = high in S
Chemical transformation of organicplant matter
•Lipids, proteins, carbos, lignin, cellulose
•Kerogens (complex heavy hydrocarbons)
•Heat -->
•Lighter hydrocarbons by breaking bonds of
kerogens
PRESENT: break fossilized chemicalbonds
•Uses:
• Drive ‘machines’
• Heat
• Electricity
•Which fuels used for which use?
• Relation of oil to gasoline
• Relation to electricity
•Sources
• Relative cleanliness
What’s in a barrelof oil?
How is electricity made and used?
Speed of Depletion of Non-renewableEnergy Sources
•How old are the sources?
•When were they discovered + put to use?
•What % have we used?
•What is projected time of depletion?
•"There are currently 98 oil producingcountries in the world, of which 64 arethought to have passed their geologically-imposed production peak, and of those 60are in terminal production decline."
Renewable alternative fuels - relate tosun’s energy
•Solar
•Wind
•Biofuels (see PPT on 203 website)
• Seed (e.g. corn) -> ethanol
• Vegetable oil (from seed) -> biodiesel
• Crop residues (e.g corn stalks) +
• Non-crop cellulose
(e.g. switch grass + Miscanthus) -> ethanol
EBI: Energy Biosciences Institute UI + U Cal-Berkeley
