The Carbon Cycle and Biofuels

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• The Carbon Cycle and Biofuels

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• http//news.mongabay.com/2005/1124-climate.html

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Soils as a source and sink of C

• A source
• Soil-C lost from cultivated land accounts for 7
  of current atmospheric Carbon.
• In one study, 5 times more CO2 was lost after one
  tillage pass compared to a no-till system within
  19 days.
• A sink
• Carbon can be sequestered in soils with proper
  management.

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Carbon Sequestration with no-till

• Switching from conventional tillage to no-till
  can sequester 168kg C/ha/year to 661kg C/ha/year.
• Depending on
• Soil texture and structure
• Climate
• What is the time horizon?

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Why does tillage increase C release into the
atmosphere?
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The answers

• Increases oxygen availability, which speeds up
  microbial activity and C evolution
• Increases contact between O.M. and soil microbes
• Tillage shifts microbial populations from fungi
  (who have a larger biomass) to bacteria

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No-till and climate change

• Gross warming potential is a calculation of the
  storage or emission of various greenhouse gasses
  under different cropping systems.

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No-till and climate change

• No-till systems can drastically reduce fuel
  consumption.

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Biofuels

• Global biofuel production in 2007
• -13.2 billion gallons of ethanol
• - 2.4 billion gallons of biodiesel
• In the U.S. this accounted for 23 of the total
  corn crop but only 3 of the nations
  transportation fuel needs.

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Corn grain ethanol

• Is corn grain ethanol a viable solution to our
  energy needs?

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Corn grain ethanol

• Corn grain ethanol has a Net Energy Balance (NEB)
  of 1.25
• Compared to Biodiesel from soybeans that has a
  NEB of 1.93
• Why is corns NEB so much lower?

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Potential scenarios for corn based ethanol
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Dissolved Inorganic N
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Worldwide Distribution of Hypoxic Coastal Waters
These dead zones are associated with major
population areas or nutrient laden watersheds
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Cellulosic ethanol

• Can use a wide range of feedstocks
• Crop residues such as wheat stubble and corn
  stover
• Residues from wood processing mills, pulp and
  paper mills and urban wood waste.
• Native grasses, such as switchgrass, or a
  diversity of native grasses
• Do you see any advantages/problems with these
  feedstocks?

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NEB of various biofuelswww.sciencemag.org August
23,2007
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Cellulosic ethanol

• Can use crops that arent also used for food and
  animal feeds
• Can use grasses that flourish on marginal lands
  as well as CRP ground
• Keep prime farmland for growing our food

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• Grow colonies of algae (a species especially
  prone to storing fat) in long, thin, transparent
  plastic bags in the desert, with CO2 pumped in
  from power plants.

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Writing Assignment 2

• Write a 1-2 pg essay on Climate Change.
• No Title Page
• Need 3 SCIENTIFIC Journal Articles
• Cite references in USDA format
• Graded mainly on content and some grammar
• 12 point font
• Due two weeks from today (April 9 or 10)