Landfill Gas As an Energy Source

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Landfill Gas As an Energy Source
Chad Elias Leisha Fong Enrique Gomez
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Components of Landfill Gas

• Creation of landfill gas
• Microorganisms break down organic material
• The decomposition results in the gas
• Composition of gas
• 50-55 methane
• 45-50 carbon dioxide
• Trace amounts of oxygen, nitrogen and hydrogen
  sulfide

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Properties of Methane

• Odorless gas
• Can cause health problems in humans
• Contribution to global warming
• 20 to 30 times more than carbon dioxide

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First Step in Production of Methane

• The waste and the oxygen mix together
• Short periods of anaerobic respiration take place
• Only carbon dioxide is produced
• The chemical equation for the process is
• C6H12O6 6O2 6CO2 6H2O

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Second Step in Production of Methane

• Aerobic resperation decreases as oxygen decreases
• An increase of fermentative and acetogenic
  bacteria activity
• Fermentative bacterium hydrolyzes the organic
  compound into VOCs, alcohols, hydrogen and
  carbon dioxide
• These products are consumed by acetogenic
  bacteria and converted into acetic acid, hydrogen
  and carbon dioxide by fermentation

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Fermentation Cycle
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Third Step in Production of Methane

• Methanogenic bacteria will extract energy from
  the fermentation waste product
• The new products are methane, carbon monoxide and
  ATP
• Methanogenic reactions
• C2H4O2 gt CH4 CO2 ATP
• 4H2 CO2 gt CH4 2 H2O
• 
  ATP

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Methane Burning

• Flaring
• The burning of methane
• Simple, but produces more carbon dioxide
• Recovery system
• Send methane into a recovery system
• More expensive, but more environmentally friendly

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Emissions Data
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Methane Gas Recovery As an Energy Source

• Methane is extracted by the means of a vacuum
  called an extraction blower
• Seperation of gases
• 120 active gases in a landfill
• Gas is cleaned and dried
• The methane component is seperated
• Methane goes through 8 12-cylinder engines that
  produce 13.6 MW

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Benefits to Converting Landfill Gas to Energy

• Reduction of odors
• Shrink landfill size
• Reduce global warming
• Decrease the dependence on fossil fuels

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Eliminating Odors

• Methane is colorless and odorless
• The combination of methane and hydrogen sulfide
  produces a foul odor
• By removing methane the odor that hydrogen
  sulfide emits is less potent

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Decreasing Landfill Size

• Landfills have a certain size that they cannot
  exceed
• Using methane for energy will reduce landfill
  size by 75
• Once a landfill is full it is capped with a
  layer of clay and six-feet of earth
• Closed landfills become parks, golf courses, ski
  slopes and even amphitheaters
• Buildings cannot be constructed because of
  constant shifts due to decomposition

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Reduction of Global Warming

• Global warming is the average increase in Earths
  temperature
• An increase in greenhouse gases causes an
  increase in temperature
• Greenhouse gases
• Water Vapor
• Carbon Dioxide
• Nitrous Oxide
• Methane

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Global Warming Statistics
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Reliance on Fossil Fuels

• Burning fossil fuels produces greenhouse gases
• Fossil fuel dependence causes political and
  economic problems
• Fossil fuels are a limited resource

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Annual Fossil Fuel Usage
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Exception Landfills

• Not all landfills are suitable
• Must have over 1 million tons
• Be in existent for at least 10 years

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Future Landfill Criteria

• Total waste accumulated
• Area, Depth and Waste Density
• Waste Records
• Contour Plots
• Total Waste Equation for Urban Population
• TotalUrban Pop x Waste Generation x Fraction of
  Waste in Landfills x Years of Land Filling x .001

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Assessment of Waste Characteristics

• Waste Characteristics
• Food and yard wastes
• Paper and cardboard waste
• Hazardous waste

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Assesment of Gas Production

• Drill tests
• Most reliable way to test
• Individual tests are done at each well that test
  for gas flow and quality
• Problems
• Not efficient
• Does not account for the quality of gas accurately

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Model Estimates

• Types of Models
• First order decay
• Waste in model places
• Data needed
• Period of filling
• Amount of Waste in Area
• Types of Waste