Methane, climate change and rice for vegetarians

Friday night in small town Arkansas means high school football.  It’s a social event for the whole town.  Some go for the spectacle, never get excited about the game and leave early.  Last night, such a fellow near me asked when I was going to write about passing gas and then left the game just before it got really thrilling.  Little did he realize that we’d had a spirited discussion about such gas and resilience just this week at Meadowcreek.

rice paddy vietnam hikersThe intestinal gas mentioned by my dispiriting friend is mainly composed of methane, as is the natural gas we use to heat and cook.  Methane (CH4) is a fascinating, but simple molecule–just a carbon molecule surrounded on all four sides by hydrogen molecules.

Methane is the second most prevalent greenhouse gas emitted in the United States. In 2013, CH4 accounted for about 10% of all U.S. greenhouse gas emissions from human activities. Methane is much more efficient at trapping radiation than carbon dioxide (CO2). Pound for pound, the comparative impact of CH4 on climate change is 25 times greater than CO2.

Methane is produced by a strange class of organisms [Archaea (Listeni/ɑrˈkə/)] the size of bacteria, but with metabolic pathways more similar to us and other organisms whose cells have a nucleus.   Some of these strange bugs live in the guts of any animal with a stomach.  They are also cultivated to produce biogas for cooking and heat.

We were talking about methane at Meadowcreek because cows are one of the big producers of methane.  Meadowcreek attracts lots of vegetarians who come armed with research showing cows produce about 20% of the methane emitted in the US.

Cows belong to a group of plant eaters called ruminants (which also include sheep, goats, camels, llamas and deer) who all have several stomachs.  Bacteria and Archaea live in these chambers and feed on the plant matter, releasing the nutritious components that the cow needs to survive. A side effect of this process is that the microbes release methane as a waste product as they feed, and this methane is burped by the cow into the atmosphere. A single adult cow can burp out as mulch as 280 liters (or 74 gallons) of methane each day.  An estimated billion and a half cows live on Earth.  So, some say cows cause global warming.

Interestingly, kangaroos have a multi-chambered stomach but methane is not a problem because their stomach microbes don’t produce it. So kangaroo meat might satisfy the vegetarians, it it was really methane that raised their ire.

Vegetarians are not likely to eat kangaroo, but many do like rice.  Rice cultivation is also a potent producer of methane–as much as 29% of methane produced by humans.  Farmers flood rice fields during the growing season.  Microbes feed on any organic matter underwater and release methane as a waste product.

Rice harvest is underway here in Arkansas, so the fields are dry and no methane is being produced.  But all summer long, the rice vegetarians love is producing as much methane as the cows they detest.

My friend at the football game wasn’t focused on global warming, just on flatulence.  So, he would be more interested to know that methane is odorless.  The odor in flatulence is caused by hydrogen sulfide gas (H2S).  While hydrogen sulfide gas is harmful in large doses, one study suggests that “a whiff here and there has the power to reduce risks of cancer, strokes, heart attacks, arthritis, and dementia by preserving mitochondria.”

Oh the many benefits of such an earthy phenonmenon.  Sniffing flatulence has health benefits and methane from animal wastes is a valuable source of fuel.

After the flatulence-oriented, flat-lined fan left, the game got really exciting and our team won with a last second field goal.  Excited kids flooded the field to congratulate their heroes, while the losers huddled on the field in prayer.  I walked off to my truck thinking about the fascinating world of methane and other natural gases.


For more on the study of the benefits of hydrogen sulfide, see this link from University of Exeter.