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LANDFILL-GAS-TO-ENERGY PROJECTS: AN ANALYSIS OF NET PRIVATE AND SOCIAL BENEFITS

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LANDFILL-GAS-TO-ENERGY PROJECTS: AN ANALYSIS OF NET PRIVATE AND SOCIAL BENEFITS. By: Paulina Jaramillo.

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LANDFILL-GAS-TO-ENERGY PROJECTS: AN ANALYSIS OF NET PRIVATE AND SOCIAL BENEFITS

By:

Paulina Jaramillo

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In addition to preventing the emission of landfill gas to the atmosphere, landfill-gas-to-energy projects could indirectly reduce air pollution from fossil fuel combustion by offsetting the use of these fuels to generate electricity.
objective
OBJECTIVE

To evaluate total private and social benefits of landfill-gas-to-energy projects.

landfill gas collection system
LANDFILL-GAS COLLECTION SYSTEM

Landfill-gas is collected by a system of wells and pipes installed throughout the landfill

Source: U.S Environmental Protection Agency. Turning a Liability into an Asset. Landfill Methane Outreach Program. Washington, DC 1996. EPA 430-B-96-0004.

collection system
Collection System
  • Will need to compare collection system capacities given with estimated gas generation
    • May need to adjust/scale systems.
    • How?
landfill gas production
LANDFILL GAS PRODUCTION
  • Amount of gas produced in year T by waste deposited in year x

Where

- T is the current year

- 2 is the Ratio of landfill gas to methane.

- Rx is the amount of waste disposed in year x (lbs).

- Lo is the total methane generation potential of the waste = 2 cf/lb

- k is the rate of methane generation = 0.04/yr

- x is the year of waste input.

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LFGT = ∑LFGT,x

Where

  • LFGT = Total landfill gas generation in year T.
  • LFGT,x = Annual landfill gas generation from waste deposited in year x.

x

case study landfills
CASE STUDY LANDFILLS

Three landfills located in St. Louis, Missouri

Source: Morgan, Susan M. and Yang, Qing. Use of Landfill Gas for Electricity Generation. Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management. January 2001.

choosing the system set up
CHOOSING THE SYSTEM SET-UP
  • Average net power generation potential during the lifetime of the project divided by the nominal capacity of each system type.
  • Determine how many engines/turbines are required and the associated capital costs.
  • The equipment with the lowest capital costs is chosen for the analysis.
air emissions
AIR EMISSIONS
  • Methane emission from landfills are reduced by generating electricity.
  • Electricity generating equipment produces CO2 emissions and emissions of criteria air pollutants.
  • Emission valuation was used to calculate total emission savings obtained using the equipment.
  • The AP-42 Emission factors were used.
uncontrolled greenhouse gas emissions
UNCONTROLLED GREENHOUSE GAS EMISSIONS

Where 0.5 is the assumed percentage of landfill gas that is CO2/CH4; 0.112 are the lbs of CO2 per cf of landfill gas; 0.041 are lb of CH4 per cf of landfill gas; and LFGT is the total amount of landfill gas generated in current year T (cf).

controlled greenhouse gas emissions
CONTROLLED GREENHOUSE GAS EMISSIONS

Where collection efficiency is assumed to be 85% and 2.75 is the ratio of the molecular weight of CO2 to the molecular weight of CH4

Similar method for other pollutants (SO2, etc)

emission offsets
EMISSION OFFSETS

Calculated using the average emission factors (based on all energy sources) for the region of St. Louis - MO, as given by the EPA’s E-GRID program.

- 1,237 lb/MWh for CO2

  • 5.2 lb/MWh for SO2
  • 2.7 lb/MWh for NOX
results for west lake landfill
RESULTS FOR WEST LAKE LANDFILL

Note: Values are in thousand dollars

sensitivity analysis
Sensitivity Analysis
  • What is most important question?
    • Under what scenarios is NPV positive!!
    • “Spider diagram” not useful itself
breakeven price of electricity
BREAKEVEN PRICE OF ELECTRICITY
  • The price of electricity at which the projects would breakeven (have NPV =0)
  • Calculated for
    • Private NPV.
    • Social NPV without emission offsets.
    • Social NPV with emission offset.
optimum subsidies method 1
OPTIMUM SUBSIDIES METHOD 1

Divide the emission savings NPV by the electricity generated during the operating life of the project.

optimum subsidies method 2
OPTIMUM SUBSIDIES METHOD 2

Subtract the private NPV from the emission savings NPV, and divide by the electricity generated during the operating life of the project.

conclusions
CONCLUSIONS
  • LFGE projects can have positive private benefits, and should be established in more landfills
  • Steam turbines provide best results, but rarely used.
  • Measuring only greenhouse gas emission reductions doesn’t tell the whole story. Criteria air pollutant emissions must be included.
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Social benefits are substantial, especially if emission offsets are included
  • Breakeven prices of electricity for these projects are competitive.
  • Optimum subsidies are much lower than available subsidies.
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