Sunday, January 24, 2016

Where does methane pollution come from?

This week we have been talking a lot about methane and its dangerous effects on the atmosphere and human health. While learning about this, it is also important to know where all of the methane is coming from in order to reduce the pollution. There are several industrial and residential uses for methane that can leak into the atmosphere, as well as some surprising sources such as animal digestive gasses.

Natural gas/petroleum:
Methane is commonly used in chemical industries, such as the refining of petrochemicals. It is used as a fuel and burned in gas turbines or steam generators to produce electricity. It is also one of the main ingredients in natural gas used in homes [1]. Each of these uses come with their own risk of leaking methane into the atmosphere unfortunately. For example, at least 1.5% of natural gas escapes into the atmosphere from the drilling extraction, to processing or transportation [1]. Over time, that can add up to a lot of methane pollution.

Animal Gas
This source might surprise some, but livestock, especially cattle, is the second leading cause of methane pollution in the U.S., constituting 25% of all methane emissions in the U.S. In fact, 3 cubic 
feet of methane is produced per pound of manure [2]. Cows and other livestock are considered ruminants, or animals that digest food in their stomachs (as opposed to intestines). The bacteria found in their stomachs helps break down the food, but also creates methane and other gases. This methane is released into the atmosphere through belching and/or excrement. [3].

Landfill Gas (LFG) is a byproduct of the natural decomposition of organic materials found in landfills. This gas is made up of half methane and half carbon dioxide, both of which are potent greenhouse gases [4]. As you can see from the graph, approximately 18% of methane pollution comes from landfills and 91% of that pollution comes from the open landfills found all over the U.S. [5]. It is also becoming clear that landfills are an untapped energy resource. Closed landfills are being used more and more to produce electricity for nearby businesses or given back to the local electricity grid. 

Coal Mining 
Methane occurs naturally in coal bed seams and can be released when coal is extracted from the ground. Coal Mine Methane (CMM) is generally trapped within the coal seam and gets exposed to the atmosphere when layers of coal face are removed. The methane is first released into the mine shaft, exposing workers to hazardous air quality, and eventually moves out into the atmosphere. 

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