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Biodegradation in Landfills: Methane Production .

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Presentation on theme: "Biodegradation in Landfills: Methane Production ."— Presentation transcript:

1 Biodegradation in Landfills: Methane Production 

2 Methane and Landfills ä Where does all the garbage go? ä How much garbage are we throwing away? ä Aren’t we recycling most of the paper that we throw away? ä Why are Landfills anaerobic? ä Methane Experiment ä Measure the methane production from various landfill components under various conditions ä Compare the energy value of the methane with the energy value of the original waste ä Issues... pH, pressure monitoring, inoculum ä Where does all the garbage go? ä How much garbage are we throwing away? ä Aren’t we recycling most of the paper that we throw away? ä Why are Landfills anaerobic? ä Methane Experiment ä Measure the methane production from various landfill components under various conditions ä Compare the energy value of the methane with the energy value of the original waste ä Issues... pH, pressure monitoring, inoculum

3 Municipal Solid Waste Management Projections Municipal Solid Waste Characterization Report (1996 Edition)

4 Solid Waste Composition in 1994 as Generated (US averages) Wood 7% Miscellaneous 9% Paper and paperboard 38% Plastics 10% Food 7% Yard waste 15% Glass 6% Metals 8% 2 kg/cap/day in 1994 The majority is organic matter!

5 Paper and Paperboard Products generated in MSW, 1995 Municipal Solid Waste Characterization Report (1996 Edition)

6 Paper Generation and Recovery Municipal Solid Waste Characterization Report (1996 Edition)

7 Landfills... ä Will continue to be the disposal option of choice ä Require long term monitoring ä ________________ ä ____________________________ ä _________________ ä ____________________ ä Will continue to be the disposal option of choice ä Require long term monitoring ä ________________ ä ____________________________ ä _________________ ä ____________________ subsidence leachate collection/treatment cover maintenance gas venting or collection

8 Biodegradation in Landfills ä Items such as paper, food, and grass clippings can be recovered relatively intact following decades of burial. WHY?? _________________ ä Landfill archaeological dating technique? ä Items such as paper, food, and grass clippings can be recovered relatively intact following decades of burial. WHY?? _________________ ä Landfill archaeological dating technique? Lack of moisture!

9 ä Why are Landfills anaerobic? ä Average temperature of Fresh Kills Landfill is 29.4 °C ä Follow carbon flow... ä Why are Landfills anaerobic? ä Average temperature of Fresh Kills Landfill is 29.4 °C ä Follow carbon flow... Methane Production Organic Matter Nutrients CH 4 CO 2 NH 3 H2SH2S H2SH2S Refractory organic matter Heat Cells H2OH2O H2OH2O New Cells

10 Fresh Kills gas production ä 12.4 Gg/day of refuse added to Landfill (tapering to zero by Dec. 31, 2001 ä Up to 10,000,000 ft 3 /day (280,000 m 3 /day) since 1982 from section 1/9 (the largest section) ä Sold to Brooklyn Union Gas Company ä $520,000/year ä 12.4 Gg/day of refuse added to Landfill (tapering to zero by Dec. 31, 2001 ä Up to 10,000,000 ft 3 /day (280,000 m 3 /day) since 1982 from section 1/9 (the largest section) ä Sold to Brooklyn Union Gas Company ä $520,000/year

11 Degradation in Fresh Kills Landfill ä How much waste is degraded to produce 280,000 m 3 /day? Cellulose, C 6 H 10 O 5, has 27 g per mole of carbon Compare with input of Gg/day

12 Gas Control ä Landfill gases are composed of methane, carbon dioxide, nitrogen, hydrogen sulfide, and ammonia (____________ hazard) ä Methane can accumulate in enclosed spaces ä Methane is _________ in air at volume fractions exceeding 5% ä Methane is often collected for use as a fuel ä Landfill gases are composed of methane, carbon dioxide, nitrogen, hydrogen sulfide, and ammonia (____________ hazard) ä Methane can accumulate in enclosed spaces ä Methane is _________ in air at volume fractions exceeding 5% ä Methane is often collected for use as a fuel asphyxiation explosive

13 keeps runoff and precipitation out of landfill safely vents gases Geomembrane Drainage Layer Cover Soil Compacted Clay WasteWaste Gas Collection Layer Gas Vent Cap System

14 Experiment Setup Hypodermic needle Crimp cap with septa Pressure sensor Anaerobic solution analog to digital Power Supply (10 V) Connector panel Multiplexer RJ 45 plug Serum bottle 35º C incubator

15 pH control... ä High partial pressure of CO 2  ____ pH ä Anaerobes require a pH between 6.5 and 7.5 ä Remember ANC... ä Volatile or Non-volatile system? ä High partial pressure of CO 2  ____ pH ä Anaerobes require a pH between 6.5 and 7.5 ä Remember ANC... ä Volatile or Non-volatile system? low

16 How much ANC do we need? K H has a value of 3.12 x moles/J K 1 has a value of moles/L Simplify alpha terms

17 ANC Problem ä How much ANC do I need to maintain a neutral pH if the pressure is atmospheric and the CO 2 fraction is 30%?

18 ANC Problem ä If I have that much ANC what will the pH be if the CO 2 pressure doubles? CO 2 pressure doubled so H + doubles pH = 6.7

19 Inoculum ä We need a few good anaerobes... ä Where could we recruit? ä How do we choose inoculum size? ä We need a few good anaerobes... ä Where could we recruit? ä How do we choose inoculum size?

20 Sample Size ä What happens if you put ¼ of a graham cracker into a 120 mL serum bottle with 60 mL of water and some inoculum and seal it? ä Estimate mass of carbohydrates at 4 grams ä Moles of carbohydrates – 30 g/mole of C ä moles C ä What happens if you put ¼ of a graham cracker into a 120 mL serum bottle with 60 mL of water and some inoculum and seal it? ä Estimate mass of carbohydrates at 4 grams ä Moles of carbohydrates – 30 g/mole of C ä moles C Bottle rocket!

21 Pressure Sensor ä Input pressure range kPa gage (15 psi) ä Output voltage mV ä We need to convert the voltage to pressure ä Input pressure range kPa gage (15 psi) ä Output voltage mV ä We need to convert the voltage to pressure

22 Time (hr) Pressure (kPa) Complications… ä Pressurized serum bottle ä Placed in incubator and monitored ä Why did pressure increase? ________________ ä What are the short term fluctuations? __________________ _____________ ä Pressurized serum bottle ä Placed in incubator and monitored ä Why did pressure increase? ________________ ä What are the short term fluctuations? __________________ _____________ Temperature! Incubator temperature fluctuations!

23 Samples for Analysis ä Bring 1 or 2 samples for methane production ä Ideas… ä ________________ ä Bring 1 or 2 samples for methane production ä Ideas… ä ________________


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