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A Sustainable Energy Future

Lester B. Lave

Carnegie Mellon University

October 24, 2006

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Is Energy Important?

• The average American uses 350 giga-joules of energy per year

• Equivalent to having 45 horses/working hour

• Or 450 workers per working hour

• Energy makes modern civilization possible

• Until 1850 use of fossil fuels negligible

• Burning fossil fuels emits CO2 & pollution

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How much Emissions Reduction?

• Kyoto calls for 10% decrease from 1990

• World needs 40%? 60% to stop carbon concentrations at 3 times preindustrial levels

• If CO2 emissions per person equal over the world, US emissions have to decline 90-95% over 1990 levels

• Need to appreciate the scale of our problem

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2 Views of Our Future

• Optimistic View: We have faced shortages of wood, whale oil, latex, tin, & many other materials: We found new technology & substitutes every time - & will in the future

• Precautionary View: Some civilizations have not been so fortunate: Easter Island. If we poison our world & squander its resources, we have nowhere else to go: Don’t jump off the cliff!

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Implications of 2 views

• Optimistic: No need to sacrifice today, technology will solve the problems. We don’t even know what we would sacrifice.

• Precautionary: Exponential growth cannot persist forever. Blind faith in technology? Our quality of life is already suffering from too many people & “toys” that use resources & give us no pleasure. 40,000 square feet houses for two …

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What Are Our Options?

1. Conservation: Use energy much more efficiently

2. Carbon capture and sequestration

3. Switch to renewable energy

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A Tale of Two Nations 2002 BTU/GDP BTU/pop GDP/pop

Denmark 38 148 39 USA 81 333 38About half the difference is efficiency & half is

lifestyleAn automobile is less than 1% efficient: 20%

of energy in the gas tank moves the wheels & 4% of weight moved is the passenger

• Driving a Hummer to a McMansion• MORE TOYS! vs. sufficient

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Conservation Without Pain

• Improve car fuel economy 30-50% by hybrids and new diesels

• Improve building efficiency by 80%

• Improve lighting, AC, etc. by 50%

With no perceptible drop in quality & some improvements

Why don’t we do it: Energy is too cheap

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Conservation: Some Pain

• Double fuel economy: Some downsizing of vehicles, light trucks for commercial use

• We can end oil imports by going to cellulosic ethanol & plug-in hybrids

• What are the costs & benefits?

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Carbon-Free Fossil Fuels• The world has abundant fossil fuels: Oil,

coal, natural gas: We will run out of atmosphere before we run out of carbon

• We have technology to capture & store 90%+ of carbon: Coal gasification, amine scrubbing, oxyfuel

• Electricity production with carbon capture or using nuclear power raises generation costs 30-40% or delivered costs 15-20%

• Costs affordable

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Confidence in Carbon Storage?

• Commercially proven carbon separation

• Use CO2 for secondary oil recovery Geologists confident CO2 pumped deep underground would stay for 1,000+ years

• No social institutions to manage this

• Need to solve problems of mining & transporting coal: Acid mine drainage, subsidence, transportation deaths

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Renewable Options• Wind, photovoltaic (PV) (solar cells), solar

thermal, dams, tides, waves, geothermal, biomass (energy crops)

• Wind cheapest in good locations, but not dependable and supply limited: Local climate effects & global climate effects

• PV is the largest resource, but expensive – sun may not shine when you need power

• Efficient, cheap energy storage critical

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Renewable Resources

• At best US Sites, electricity is generated 1/3 of the time: Need 3 times the wind capacity even with free storage

• At best US sites, PV generates electricity 22% of the time – need 5 times capacity

• Or we can modify demand to take power only when it is available – Regulate our activities by the sun and wind?

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Other Renewables

• In addition to wind and photovoltaic cell, there are river dams, tides, waves, geothermal, & biomass

• All, except solar, have limited capacity – they can contribute, but not satisfy our demand

• All have adverse environmental effects

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Energy for Transportation• Cars, trucks, aircraft, ships, trains major

energy users & CO2 emitters

• No way to capture CO2 – don’t produce it!

• Biofuels is the short-term answer

• Hydrogen economy?: Energy source?: H2 is an energy carrier, like electricity

• H2 difficult to transport & store – dangerous

• H2 unlikely to be commercial for 20-30 yrs

• H2 advantage: Water (H2O) is only emission

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A Primer on Biofuels

• Plants 1-2% efficient in using sunlight (solar cells about 10% efficient now)

• Oil yield per acre from soybeans, corn rape seed, etc. is low

• Bio-diesel from cooking fat, animal parts is great, but growing crops less attractive – thus supply is limited

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Corn or Switchgrass?• The export market for corn is disappearing

• Stop soil loss & pesticide & fertilizer runoff

• Switchgrass improves soil quality

• Potentially greater profit from farming switchgrass – no subsidies

• Return much of Great Plains to prairie grass

• Annual harvest (mowing hay)

• Let herds of bison & elk roam

• More diverse, natural ecology

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Switchgrass Production Limits

• How much farmland is available?

• US can produce 40-60 billion gal/yr

• Switchgrass farming potentially profitable

• Going to lower quality land raises harvesting & shipping costs

• Brazil, Argentina, & many nations would produce ethanol from switchgrass, bagasse, trees and other biomass

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Biomass Ethanol Advantages

• No net CO2 to atmosphere – plants grab CO2 for cellulose – which is returned when ethanol is burned

• During fermentation, a pure stream of CO2 can be captured & sequestered – a carbon pump taking O2 from the atmosphere

• Sustainable fuel supply that eliminates many current farming problems & produces better soil for the future & biodiversity

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Eliminating Gasoline from USA• USA uses 140 billion gallons of gasoline/yr• Equivalent to 200 billion gallons of ethanol• Hybrid electric vehicle can get 40% more

miles per gallon of fuel – need 120 B gal• 90% of trips less than 30 miles 75% of fuel• Plug-in hybrids use electricity for 30 miles• Need only 40 B gallons of ethanol!• PHEVs can eliminate need for gas in cars• Or Smaller, less powerful hybrids: 60 B gal

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Conclusion

• 90-95% reduction in CO2 is our goal• For factories & homes, use electricity from

fossil fuels with carbon separation & storage, or nuclear, or renewables

• For transportation, biomass ethanol: Plug-in hybrids or smaller hybrids

• Costs & inconvenience modest• Barriers: Lethargy & low fossil fuel prices –

need a CO2 or oil tax

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Importance of Life Cycle Analysis

• Carnegie Mellon Green Design Institute: www.gdi.ce.cmu.edu

• Input-Output Life Cycle

Assessment: www.eiolca.net. • Book: Environmental Life Cycle

Assessment of Goods & Services: An Input-Output Approach, 2006.

• Available at Resources for the Future or Amazon