1. Calculation of Gas Production

2. Problem 1: Gas Potential  Calculate the gas potential in m 3 /tonne of waste received for a waste having the following chemical formula. Assume that the waste is 79.5% organic and 50% of the organic mass is biodegradable.

3. Stoichiometric Potential

4. Step 1: Calculate the Methane Moles MSW Chemical Composition: Normalizing to Carbon: Each mole of degradable MSW produces: Moles CH 4

5. Step 2: Calculate the mass of Degradable MSW 1 tonne = 1000 kg Assume MSW is 79.5% organic, 50% of which degrades:

6. Step 3: Calculate the No. of Moles MSW MW of MSW = 23.9 g/mole 16,631 moles MSW/tonne MSW x 0.531 moles CH 4 /mole MSW = 8,831 moles CH 4

7. Step 4: Calculate the Methane Potential (L o ) At STP, 22.4 L/mole of Gas 22.4 L/mole x 8,831 moles/tonne MSW = 197,915 L = 198 m 3 /tonne MSW

8. Class Example Calculate the Methane Potential for the following MSW Chemical Composition: Assume this represents 65% of the total waste and is 50% degradable.

9. Problem 2: Gas Production Rate

10. Example Problem A landfill cell is open for three years, receiving 165,700 Mg of waste per year. Calculate the peak gas production if the landfill gas emission constant is 0.0307 yr -1, the methane generation potential is 140 m 3 /Mg. Use an electronic spread sheet to complete this problem

11. Example Problem Calculations:  2kL o M i = 1424000  Col. 21424000*EXP(-0.0307*t)  Col. 31424000*EXP(-0.0307*(t-1))  Col. 41424000*EXP(-0.0307*(t-2))

12. Example

13. Example Problem

14. Class Example A landfill initially receives 1000 tons/day (2000 lb= 1 ton) of waste. This receipt rate increases 10% per year. The landfill is closed at the end of the fourth year. Using the EPA exponential model (k = 0.0303, L o = 140 m 3 /Mg, calculate the yearly gas production for 20 yrs after opening. What is the peak gas production in m 3 /yr? Repeat for k = 0.307 /yr. Plot both curves.

15. Return to Home Page Last updated July 2004 by Dr. Reinhart