The Effects of Methane on the Atmosphere

Methane, a gas, has one molecule of carbon and four of hydrogen. It has no detectable odor and has lighter-than-air qualities. Anaerobic bacteria, one of the oldest lifeforms on Earth, manufacture methane by stripping it down into organic material and digesting it; they expel gas (methane) as a waste product. We have uses for methane today, since we use it as a natural gas and means of energy. Methane has a direct effect on the atmosphere when it combines with other substances and chemicals. It can be a problem if its concentration exceeds tolerable limits.

Global Warming

• Although methane does not exist in the atmosphere in the amounts that CO2 does, it has 21 more times the strength of CO2 as a greenhouse gas. Methane has increased more rapidly in the atmosphere, compared to CO2. Methane can remain in the atmosphere for about seven years. It traps heat in a greenhouse effect, reflecting heat through infrared radiations, which travels back down to the Earth. Methane can speed up global warming, resulting in more powerful hurricanes and flooding.

Sources and Concentrations

• The production of methane in concentrated amounts that become dangerous to the atmosphere come from coal mining and burning, heavy industry involving the combustion of petroleum and natural gas, and animal agriculture. Secondary sources include manure dumps, wastewater treatment plants, sludge ponds, swamps, ocean sea floors, landfills and silt-clogged rivers and streams.

Atmospheric Health -- Lower Levels

• When methane reaches a toxicity level higher than 5 percent, or 50,000 parts per million, it begins to displace oxygen levels in the lower and upper atmosphere. It can cause oxygen deprivation, which leads to asphyxiation. There must be 18 percent available oxygen in the atmosphere for proper human respiration and heath. Oxygen levels between 12 and 16 percent result in rapid breathing and increased pulse rate. Some signs of muscular loss of control can be present.

Atmospheric Health -- Higher Levels

• When the oxygen level reaches 10 to 14 percent, signs of labored and disturbed respiration appear, along with increased fatigue from normal exertion. A 6 to 10 percent oxygen level induces vomiting and nausea, loss of consciousness or collapse and an inability to move freely, due to lack of muscle control. Oxygen levels under 6 percent can account for convulsions, gasping for breath and can lead to complete respiratory failure and death.

Explosive Nature of Methane

• Methane, when found in a confined area, can cause explosive conditions. When the amount of methane in the air ranges from 5 to 15 percent, any type of spark can cause ignition. Very heavy concentrations of methane can make it flammable, easy to ignite if the right conditions exist. The air in coal mines and landfills must be monitored on a constant basis for just this reason.