Energy > Climate Change
November 2021
Methane – powerful but short-lived
This article is the ninth in a series focused on the causes and consequences of a warming planet
We are all familiar with natural gas. It plays a very important role in our lives. We may use it to heat our home and office, power our water heater, and heat our stove.
Methane is the primary component of natural gas. When natural gas (methane) is burned, carbon dioxide is emitted, just like with other fossil fuels. But burning natural gas emits only about half the amount of carbon dioxide as coal. Natural gas is sometimes considered a "transition" fuel in the process of moving from coal and oil to clean energy, such as solar and wind.
However, a problem occurs when natural gas (methane) is not burned but escapes into the atmosphere. This can occur when a pipeline leaks. An example is Aliso Canyon in California where a leak led to the escape of over 100 thousand tons of methane in a four-month period.
Methane in the atmosphere is a powerful greenhouse gas. According to the EPA, methane is about 120 times more powerful as a greenhouse gas than carbon dioxide when compared per unit of mass. But its lifespan in the atmosphere is on average about 12 years (compared to hundreds of years for carbon dioxide). If both power and lifespan are taken into account, methane is still about 25 to 36 times more powerful than carbon dioxide. Converting the atmosphere’s methane content to a carbon dioxide equivalent, methane emissions make up about 10% of US greenhouse gas emissions.
Cattle have a unique digestive system where fermentation breaks down the feed for digestion. This process produces methane which is exhaled into the atmosphere by the animal. High quality feed, cattle breeds, and higher feed efficiencies result in fewer emissions. So Iowa cattle produce fewer emissions than those in developing countries. Research is being conducted on ways to further reduce these emissions.
Livestock manure produces methane when it is stored or treated in anaerobic conditions (without oxygen). This is usually manure in liquid form kept in pits, tanks, and slurries. But this manure can be processed by means of "anaerobic digestion" where biogas is produced that can be used as an energy source.
Methane is produced and emitted in low oxygen environments like wetlands where the soils are water-logged. Methane is also emitted from landfills.
Don Hofstrand, retired extension agricultural business specialist, agdm@iastate.edu
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University
