Methane: the second culprit

- Advertisement -

It wasn’t until 2001—when the UN-sponsored Intergovernmental Panel on Climate Change (IPCC) submitted its report—that methane was finally given much-needed attention as “one of the most potent greenhouse gases on Earth.”

“Methane absorbs heat 21 times more than carbon dioxide and it has 9-15 year life time in the atmosphere over a 100-year period,” said Dr. Constancio Asis, Jr., a recipient of the 2011 Norman E. Borlaug International Agricultural Science and Technology Fellowship Award.

That’s disturbing. But what is more alarming is this report published in www.the “While carbon dioxide in the atmosphere has increased steadily, methane concentrations grew relatively slowly throughout the 2000s, but since 2007 have grown 10 times faster.  Methane increased faster still in 2014 and 2015.”

The report said that about 60% of all methane emissions comes from human activities. These include living sources: livestock, rice paddies and landfills, as well as fossil fuel sources, such as emissions during the extraction and use of coal and natural gas.

Methane was first scientifically identified by Italian physicist Alessandro Volta in 1776.  He collected some “flammable air” from the marsh straddling Italy and Switzerland.  It wasn’t until in 1778 that he was able to isolate the pure gas.  The person credited for naming it as “methane” was German chemist August Wilhelm von Hofmann who derived the name from methanol.


Today, it is commonly known that methane is a very simple molecule (one carbon surrounded by four hydrogen atoms) and is created predominantly by bacteria that feed on organic material. “In dry conditions, there is plenty of atmospheric oxygen, and so aerobic bacteria which produce carbon dioxide are preferred,” explained Dr. Schmidt.

Although a non-toxic, colorless and odorless gas, methane is highly combustible.  At room temperature, methane is a gas less dense than air.  It melts at –183°C and boils at –164°C.  It is not very soluble in water. Methane is combustible, and mixtures of about 5%-15% in air are explosive.

Methane, like carbon dioxide, is a greenhouse gas.  Also included are chlorofluorocarbons (usually released from air conditioners and refrigerators) and the nitrogen compound (particularly, nitrous oxide, which comes from burning fossil fuels and fertilizers).  Ground-level ozone, produced by burning fossil fuels, is also considered a greenhouse gas.

“Even if we were able to stop them tomorrow, these greenhouse gases will continue to have an effect for centuries,” Secretary-General Michel Jarraud of the UN World Meteorological Organization said in a statement quoted by the Agence France Presse (AFP).

In 2015, the IPCC said methane accounted for about 16% of global greenhouse gas emissions.  In comparison, carbon dioxide accounted for more than three-quarters of plant-warming emissions.


According to a report, methane concentration in the atmosphere is “growing faster than any time in the past 20 years. The increase is largely driven by the growth in food production.”

The report considered methane from food production as the next wildcard in climate change.

“If we cut methane emissions now, this will have a rapid impact on methane concentrations in the atmosphere and therefore on global warming,” it pointed out.

The Philippines is one of the contributors of methane emissions. In 2014, for instance, the country’s total methane emissions was approximately 41.87 million metric tons of carbon dioxide equivalent.

Most of these emissions come from rice cultivation.   The Philippines is one of the world’s top rice producers.  Flooded rice paddies emit as much as 500 million tons of methane, around 20% of total manmade emissions of this gas, according to the Laguna-based International Rice Research Institute (IRRI).


In Isabela State University, a study funded by PCARRD showed that by using simple science-based strategies, farmers can contribute significantly to the reduction of methane emissions.  For instance, mid-season drainage of irrigation water reduced methane emission by 48%.  This emission is valued at P34.16 million, based on the 2009 World Bank price of US$12 per ton of carbon dioxide and exchange rate of P48 per US$1.

Meanwhile, composting of rice straw resulted in 64% less methane emission released in the air.  By combining mid-season drainage and application of rice straw compost, methane emission is further reduced by 81%.

“By shifting to climate-change friendly farming practices, as what was done in the 7,789.34 hectares of lowland irrigated rice in Isabela, farmers can get incremental benefits amounting to as high as P138.95 million per year,” the PCARRD report pointed out.

Rice farmers can also help reduce methane emissions into the atmosphere by adopting controlled irrigation or alternate wetting and drying (AWD) technology.

Developed by the Laguna-based International Rice Research Institute (IRRI), AWD is a technology which allowed rice fields to dry for a certain period before applying irrigation water.

Also called controlled irrigation or intermittent irrigation, AWD technology can actually save farmers almost one-third of irrigation water without sacrificing yields.  It also saves farm inputs like oil, fuel, and labor being utilized on the operation of water pumps.

On an 8-season field experiment conducted at IRRI, it was found that AWD “has real potential to reduce the global warming impact of paddy fields to one-third of the conventional continuously-flooded field water management.”

In a paper presented during the international workshop on “Water Management and Technology for Crop Production under Climate Change” in Suwon, Korea, the authors claimed AWD “can reduce methane emissions by over 40%.”


Livestock are another major contributor of methane.  In 2006, the amount of methane emitted by farm animals alone exceeded that of the iron, steel, and cement industries combined. “Livestock are one of the most significant contributors to today’s most serious environmental problems,” said Henning Steinfeld, a senior United Nations official.

“Animals emit not carbon dioxide, but methane which is at least 25% more damaging than carbon dioxide. There is recognition by the United Nations, that while all means of transportation, from cars to planes, contribute to 13% of emissions, cows do with 18%,” wrote Roberto Savio, co-founder of Inter Press Service.

President of the National Academy of Sciences Ralph Cicerone has indicated the contribution of methane by livestock flatulence and eructation to global warming is a “serious topic.”

Cicerone, an atmospheric scientist, said: “Methane is the second-most-important greenhouse gas in the atmosphere now. The population of beef cattle and dairy cattle has grown so much that methane from cows now is big. This is not a trivial issue.”

The digestive system of ruminant animals such as cattle and goats contain anaerobic bacteria and thus produce methane gas.  A single cow belches out 100 gallons of methane gas a day.  The raising of these animals along with sheep, carabao, and swine has contributed to the methane production in the Philippines.

Among these animals, cattle are by far the largest contributors to global enteric methane emissions, as they are the most numerous and have a much larger body size relative to other species such as sheep and goats.  As of July 1, 2017, the total number of cattle in the country was estimated at 2,561,270 heads, reports the Philippines Statistics Authority.

A recent study showed that emissions of methane from livestock are larger than previously thought.  An AFP report said: “Revised calculations of methane produced per head of cattle show that global livestock emissions in 2011 were 11% higher than estimates based on data from IPCC.”

Prof. Dave Reay, from the University of Edinburgh, was quoted as saying: “As our diets become more meat- and dairy-rich, so the hidden climate cost of our food tends to mount up.” He added: “Cows belching less methane may not be as eye-catching as wind turbines and solar panels, but they are just as vital for addressing climate change.”

To which Nicholas Stern, author of the 2006 Stern Review on Climate Change, also suggested: “People will need to turn vegetarian if the world is to conquer climate change.”



More Stories