Question

Consider a mid-size city of 3,000,000 people in the Cairo city . Suppose that its residents produce, on average, 6.0 kg a day of MSW. At present this waste is being hauled 180 miles away (in a southeasterly direction) where it is being used to fill in an abandoned open pit nickel mine. The mine and deposited wastes abut a shallow marine embayment. Seaweed, shellfish, crustaceans, and fish are harvested from this embayment and eaten by both the local fishermen and their families as well as by the residents of the city.

Facts about the waste:

55 % of the waste is composed of agricultural waste and household non-sewer organics

35 % of the waste is household waste, including paper, glass and plastics

10 % of the waste is a combination of metal, wood, chemical, petroleum, and other miscellaneous materials.

Calculate how much methane could be generated from the anaerobic decay of the landfill waste over a 10 year time period. What, if anything, could be done with this methane? Would more, less, or the same amount of methane be produced if the waste was simply incinerated? Which waste disposal method provides the biggest threat to environmental sustainability and human health? Explain your answer.

Answer 1

Total Waste generated per day, MSWt = Waste generated per person*Number of person = 6*3000000=1800000 Kg/day=1800 Ton/day

Degradable organic carbon, DOC=0.4A+0.17B+0.15C+0.3D

where fractions, A?=?paper, cardboard and rags, B?=?leaves, straw and others, C?=?fruit and vegetable wastes and D?=?wood

In our case, A=.35

B=0

C=.55

D=0.1

=>DOC=0.4*.35+0.17*0+0.15*.55+0.3*.1=0.25

MSWF?=?the fraction of MSW that reaches the landfill sites =1

MCF?=?Methane correction factor=1 (Assumed)

DOCF?=?the value of the dissimilated fill gas, which was considered 0.77 at a temperature of 35?°C

F?=?fraction of methane gas, which was considered 0.5

R?=?recovered methane gas=0, since we are not convering Methane

OX?=?oxidation factor, which was also considered 0 (Anaerobic decay)

=> Methane produced per day = 1800*1*1*.25*.77*.5*(16/12-0)*(1-0)=231 ton/day

for 10 years, Methane produced = 231*365*10=843150 ton

Methane produced can be stored and then use as a Fuel for Power generation

b) If waste is simply incinerated, in normal operation, CO2 and other oxygenated products form. Therefore, Methane will be produced in less amount in incineration in comparison to land filling anaerobic decay

c) Global warming potential of CH4 is 86 while CO2 is 1 only. I means 1 gram of CH4 emitted to environmental will cause 86 times more harm w.r.t Global warming in comparison to 1 gram CO2 emmited. Hence, land filling is more hazaroudous to environment (Since this process liberated CH4) than incineration