Overview of Biofuels: System Approach and Analysis

1
Overview of Biofuels  System Approach and
Analysis

• Prof. Steven G. Buckley
• MAE 118b
• February 21, 2007
• (Slides 14-23 from presentation by Melanie
  Zauscher)

2
Taking a systems approach to biofuels
3
Biofuels in perspective

• Total world power draw 15 TW
• Total world solar flux 120,000 TW
• So this should be easy, right?
• Earth intercepts 8000 times more power than we
  use.

4
Going green the reality

• 29.2 of earth is land
• 18.8 of the land is arable (CIA World Factbook)
• Photosynthesis is 6 efficient at best, 1 is
  reasonable average given ground coverage, etc.
• So far 8000 0.292 0.188 0.01 ? we still
  have 4.3 times as much energy as we consume!
• (but this is if we take 100 of the arable land)

5
Problem of food production

• 11 of land area is in cropland (Worldwatch)
• Assuming this is all arable land ? 7.8 of land
  remains
• 23 of land area is in pastureland (assume that
  much of this is non-arable, but some of this is
  arable)
• Sobering fact
• 1960, 0.5 hectare of cropland per person,
  considered adequate for healthy diverse
  omnivorous diet
• 2000, 0.23 hectare of cropland per person
• Declining quality and quantity

6
Conversion efficiency to fuel

• Energy stored in plants is recovered at what
  rate?
• Direct combustion best biomass combustion plant
  efficiency 20 conversion into electricity
• Production of biofuel this is an open question!
• Currently 10 billion gallons of both ethanol
  and 1 billion gallons of biodiesel are produced
  annually, worldwide (various sources)
• Gasoline consumption, worldwide 300 billion
  gallons
• Diesel consumption, worldwide ?
• 30 billion gallons of diesel in the U.S., annually

7
Biodiesel yield for some common crops
From Wikipedia / biodiesel, reference
http//www.globalpetroleumclub.com/
8
Questions to ask

• What are the resource inputs?
• Fertilizer, pesticides
• Transportation
• Harvesting
• Processing
• What is being displaced / used?
• Food crops
• Water
• Forest, other land uses

9
As always, defining system boundaries is crucial!

• Example how do you define the energy return on
  energy invested for biofuels?
• DOE, 2006
• Corn-based ethanol 1.36 today
• Biodiesel 3.2 today
• Institute for Local Self-Reliance
• Best corn-based ethanol 2.09
• Best cellulosic bioethanol 2.62
• Biggest academic critics Prof. David Pimentel
  (Cornell), Prof. Tad Patzak (U.C. Berkeley)

10
Critics point to flaws in analyses of biofuel
energy balances and net carbon efficiency

• Most fertilizers (e.g. urea, CO(NH2)2 have a
  common ammonia (NH3) feedstock
• Tremendous amounts of energy are used in
  fertilizer manufacture
• Some amount of this potent greenhouse gas escapes
  during manufacture, and nitrogenous fertilizers
  convert to greenhouse gases ? converting into
  more greenhouse gas equivalents than simply
  burning an equivalent energy content of gasoline

11
Reading

• H. Shapouri et al. THE 2001 NET ENERGY BALANCE
  OF CORN-ETHANOL
• www.ethanolrfa.org/objects/pdf/net_energy_balance_
  2004.pdf
• David Pimentel and Tad Patzek, "Ethanol
  Production Using Corn, Switchgrass and Wood",
  Natural Resources Research (March 2005), pp 65-76
  
• http//petroleum.berkeley.edu/papers/Biofuels/NRRe
  thanol.2005.pdf

Conclusion this is a close call!
12
Why bother with biofuels?

• Critical need for liquid transportation fuels
• Peak oil
• Geopolitics
• Climate change threat

13
Ethanol and Biodiesel are oxygenated fuels
derived from plant sources

• Oxygen on-board the fuel molecule
• Reduces incomplete combustion
• Promotes CO ? CO2 and oxidation of soot particles
• The bonded O does not add to thermodynamic energy
  content
• Less energy per unit mass or unit volume of fuel
• Production processes are plant-specific

14
Gallons of Gasoline Equivalents
http//www.nafa.org/Content/NavigationMenu/Resourc
e_Center/Alternative_Fuels/ Energy_Equivalents/Ene
rgy_Equivalents.htm
15
Biodiesel

• Made from vegetable oil or animal fat and
  methanol or ethanol
• Locally produced, renewable, simple to make and
  use
• Can use same infrastructure as petrodiesel
  including engines
• Sold as B2, B5, B20, B99 B100

16
Trans-esterification Reaction
This is most common way to reduce oil viscosity
17
Biodiesel Production Facilities
From the National Biodiesel Board
18
Biodiesel Retailers
From the National Biodiesel Board
19
Issues with Biodiesel

• Material compatibility
• Biodiesel can dissolve neoprene rubber hoses and
  o-rings in fuel lines of older vehicles
• Same problem with ULSD, so new cars are
  compatible already
• Cold temperature problem
• Tendency to cloud and stop flowing in cold
  climates
• Shelf life
• No more than 6 months

Pahl 2005
20
Ethanol
Made from sugar, starch or biomass Locally
produced, renewable Can use limited gasoline
infrastructure, and only small blends on most
gasoline engines Sold as octane enhancer, E10,
E25, E85 and E100
21
Issues with Ethanol

• Can't transport it in pipelines
• Absorbs water
• More expensive to ship
• As E-85, has reduced MPG, so fuel costs more even
  when ethanol is cheaper than gasoline
• Hard to find E-85
• A 2002 DOT/DOE study found 1 of all flex-fuel
  cars use E-85, but automakers still get credit
  for CAFE standards

http//www.nhtsa.dot.gov/cars/rules/rulings/CAFE/a
lternativefuels/analysis.htm
22
Ethanol in California

• Current annual demand of ethanol is estimated
  950 million gallons
• Demand about ¼ of national supply
• Demand mostly to replace MTBE with (5.7) ethanol
• Current CA annual production is 25 million
  gallons
• 95 of ethanol delivered to CA is transported via
  rail cars
• 1 million barrels of foreign ethanol were
  imported in 2004-2005

Perez 2005
23
Only one public ethanol (E-85) station in
California and that is in San Diego!
24
What is the future of biofuels?

• Not only are we carbon-constrained, we are
  land-constrained!
• How does peak oil influence the problem?
• Is the energy balance gt 1 or lt 1?
• Please read the Pimentel and Patzek paper for
  Friday
• http//petroleum.berkeley.edu/papers/Biofuels/NRRe
  thanol.2005.pdf