Environmental Microbiology of Aquatic and Waste Systems

300 11 The Disposal of Municipal Solid Wastes

greenhouse gas and has 25 times more heat trapping
potential than carbon dioxide (CO 2 ). However, methane
is only present in the atmosphere at concentrations
around 1,800 parts per billion (as opposed to CO2’s
385 ppm).
There are many factors that determine how much
landfill gas, including the valuable methane, a given
landfill will produce. The most important factors for
predicting the quality of the landfill methane that will
be produced over the lifetime of a landfill are:

1. Waste composition
   The more organic waste present in a landfill, the
   more landfill gas (e.g., carbon dioxide, methane,

nitrogen, and hydrogen sulfide) is produced by the

bacteria during decomposition. The more chemicals

disposed of in the landfill, the more likely non-meth-

ane organic compounds (NMOCs) will be produced

either through volatilization or chemical reactions.

2. Age of refuse
   Generally, more recently buried waste (i.e., waste
   buried less than 10 years) produces more landfill
   gas through bacterial decomposition, volatilization,
   and chemical reactions than does others.


3. Moisture content
   The presence of moisture in a landfill increases
   gas production because it encourages bacterial

O

O H

N

R

OH

HN

N

F 420 (oxidized)

N H

CO 2 −

P O CH 3

O H

S

H

H - S - HTP

H

O

NH 3 +

R

1

2

4 3

5

MFR

5

N N N

N

O

H

H 2

HN

N R

H

H

I

1

2

3

4

6

8 7

H 4 MPT

H

S

SO 3

H-S-CoM

Fig. 11.11 Some
coenzymes peculiar
to methanogens (From
DiMarco et al. 1990. With
permission)

Table 11.6 Methanogenic genera among the archeae (Modified from http://www.earthlife.net/prokaryotes/euryarchaeota.

html, and http://en.wikipedia.org/wiki/Methanogen, Anonymous 2010i)

Methanogenic archaea Number of species Cell morphology Example

Methanobacterium 19 Long rods Methanobacterium bryantii

Methanobrevibacter 7 Short rods Methanobrevibacter ruminantium

Methanosphaera 2 Cocci Methanosphaera stadtmanae

Methanothermus 2 Rods Methanothermus fervidus

Methanococcus 11 Irregular cocci Methanococcus deltae

Methanomicrobium 2 Short rods Methanomicrobium mobile

Methanogenium 11 Irregular cocci Methanogenium frigidum

Methanospirillium 1 Sprilla Methanospirillium hungatei

Methanoplanus 3 Plate-like Methanoplanus limicola