Environmental Engineering Reference
In-Depth Information
are found in the tundra, where cold temperatures persist in the shallow regions of the permafrost. The tundra's
methane comes from decomposing plants and animals trapped in the permafrost. Methane hydrates also are
found deep in the ocean, where the pressures are high and the temperatures are low, forming at depths greater
than 500 meters and, in some parts of the deep oceans, may be very thick. The following figure shows the loca-
tions of known methane hydrate deposits. If used at their current rate, there may be a 350- to 3,500-year sup-
ply. Although not recognized as a fossil fuel at this time, another source of methane gas is that which escapes
from pockets of fossil fuels in the deep oceans.
Two major issues are associated with the use of methane hydrates as a source of energy:
• The cost of locating and "mining" the methane hydrates
• The concern that methane, a greenhouse gas, will be released while obtaining and processing the meth-
ane, thus speeding up global warming
Source: Naval Research Laboratory
Methane hydrates made the news during the attempts to contain the
Deepwater Horizon
oil spill in the Gulf of
Mexico in 2010. As the crude oil poured out of the broken well, methane also leaked out, and at the low-tem-
perature depth of the broken oil well, methane hydrates formed. The methane hydrates made it difficult to in-
stall a containment system to help control the flow of crude oil and blocked the openings to the containment
system.
Extraction and Purification of Natural Gas
Once a hole is punctured into a natural gas reservoir, the gas usually flows from wells under its own pressure.
Natural gas is collected by small gas lines that are then connected to larger gas lines. These transmission
pipelines move the natural gas great distances to areas where natural gas is present in low quantities or does
not exist at all, or where the population and demand exceed the natural supply. Natural gas requires processing
