Welsh Poultry Centre

What's all the fuss about Methane?

Methane is, inchemical formula, CH4, that is 1 carbon atom and 4 hydrogen atoms. When burnt,methane produces Carbon Dioxide CO₂ and Water, H₂O. CO₂is believed to make up 92% of all greenhouse gases whereas methane is believed to make up the remaining 8%. However methane is considered such a problem because its greenhouse effect, or Global Warming Potential, (GWP), is estimated at 20 times that of Carbon dioxide. That is to say it is 20 times more effective at preventing infrared radiation escaping from the planet. Methane in the atmosphere has increased 150% since 1700 whereas Carbon Dioxide has increasedby 35%.

From: www.atmosresearch.com/

Ice core and atmospheric records of the increase in atmospheric methane from pre industrial times to the present. (source: Ethridge et al. 1998)

Is Methane the problem?

On the face of it methane is more of a problem than CO₂, however, methane has a life in the atmosphere of only 12 years whereas CO₂ has a lifetime of between 50 and 200 years in the atmosphere. It is worth remembering that the movement of carbon is dynamic. Carbon is constantly being released into andtaken out of the atmosphere. This is a necessary cycle that fuels life

Where does Methane come from?

There has always been methane in the atmosphere. Records from ice cores (see above), suggest that the level of methane was fairly constant until the start of the industrial revolution when it started increasing. Most natural methane comes from wetland but oceans also produce methane and large amounts of methane are trapped in permafrost and in ice. Owing to a gut bacteria, termites produce, 10% of all naturally produced methane. On the man made side, burning fossil fuels or biomass produces methane, mining releases methane and leakages from natural gas (which contains methane) pipelines and of course from ruminants

Wetlands (includes RiceAgriculture).......................................37

Ocean Faults/Fissures...........................................................3

Energy Consumption ...........................................................18

Livestock/Ruminants (Cows, sheep,etc.)......................................19

Landfills/WasteTreatment.....................................................11

Biomass Burning ................................................................7

 Thesefigures are global. The UK figures below do not include natural emissions.

In2009, methane emissions, excluding those from natural sources, were 61% below 1990 levels. In 2009, the main sources of methane were agriculture (41%) and landfill sites (37%).

From DEFRA website

As you can see the figures for methane have been falling over the last 20 years in the UK and globally.

Variations in annual change in atmosheric methane concentration from 1983 to 2009, from Dlugokencky et al (2009). Measurements are in parts per billion, per year

From: www.amazingcarbon.com/

Livestock's Long Shadow

BeforeI talk about this decline in global methane over the last twenty-five years, Ineed to mention the United Nations FAO report, "Livestock's Long Shadow" published in 2006. The highlights of this 400 page report state that livestock is "responsible for 18% of greenhouse gas emissions", which is greater than the emissions from all global transport systems combined. It goes on to say "The production of cattle to feed and clothe humans stresses ecosystems around the world, and is assessed to be one of the top three environmental problems in the world on a local to global scale"

The headline-grabbing figure is the 18% contribution that livestock make to greenhouse gas emissions.  This figure is predominantly made up of indirect greenhouse gas emission resulting from livestock farming, such as: the clearing of rainforest; the burning of fossil fuels for the production of soluble fertilisers; the oxidization of carbon from cleared land and the break down of fertilisers in manures.

Indeed if the methane produced by the ruminants was a major cause of the increase in atmospheric methane then one could expect atmospheric methane and ruminant numbers to show some correlation. However ruminants, which include buffalo, goats, sheep, camels, giraffes, reindeer caribou bison and antelopes existed in greater numbers pre 1700 than today.

The Decline in Methane

Although there are variations in the evidence of when the decline in methane started, some suggesting twenty five years ago while others suggest 10 years ago, everyone agrees that it is declining. This does not conform to existing theories and forecasts and has left scientists unsure of where the reduction iscoming from. It has been suggested that it is due to better control of leaks on the Tran Siberian pipeline, while others have suggested that slightly cooler oceans has seen a reduction from this source.

So are cows the problem?

Research by Dr Mark Adams, Dean of the faculty of Agriculture at Sydney University has shown that one ha of grassland can sequester as much methane as emitted by 162 cattle in an entire year. This is because certain bacteria in biologically active soil  utilise the methane as their sole energy source. This means that the methane that cattle emit has a very short cycle, returning to the grassland in a similar way to water vapour transpired by pasture returns as dew, rather than reaching the upper atmosphere.

There is some evidence to suggest that high yielding, soluble nitrogen dependent grasses increase the amount of methane emitted as the methane dependent bacteria do not develop. Research by Bristol University noted that there was a reduction in methane when Birds Foot Trefoil was part of the ration.

Demand for Meat

Livestock's Long Shadow also highlighted the increased demand for meat. It is a well documented statistic that as societies become richer they eat more meat and dairy products.

Meat consumption and income 2002

From: Livestock's Long Shadow

However,despite pointing out in the report that "livestock now consume more human edible protein than they produce" (77 million tones of protein consumed toproduce 58 million tones of protein), the report advocates the intensification of livestock to meet the increasing demand and minimize greenhouse emission. In 2010, a diet was proposed to reduce the emissions of greenhouse gases by cattle. The diet was conceived by Alexander Hristove of the Pennstate University. Cattle are fed a concentrated high corn diet which produces rapid weight gain thereby reducing methane emissions because the animal reaches maturity quicker so there is less cattle at anyone time. However it takes no account of the carbon emissions pproducing the corn, fertiliser, pesticides, herbicides, possible soil oxidasation and the decline in water quality. In the UK we are similarly looking at reducing emissions be increasing efficiencies, effectively thereby reducing cattle numbers. 

The alternative would be eating less meat but eating meat that comes from well managed livestock grazing systems. In this way the cattle then become carbon sinks rather than carbon sources.

Indeed the most effective way to restore land that has been degraded through conventional cropping (organic matter percentage of continually cropped land inthe East of UK is now critically low,) is through the establishment ofappropriately grazed perennial pasture.

Livestock, and beef/dairy in particular, are not the problem. The problem is the way in which we are producing our beef/dairy and the amount that we demand. Well managed, rotationally grazed perennial grassland could sink more carbon than it produces as well as producing a more healthy food for humans. The ruminant is an amazing digestive system that could allow us to utilise grasses efficiently. Grassland in turn has the ability to sequester more carbon than a rainforest.Consider the vast herds of bison and other ruminants that maintained the great grassland of the past and remember, grassland can sequest more carbon than a rainforest. It is the cropping of these vast grasslands that has released carbon, not their maintenance by ruminants.

The Future

Throughout human history population has been limited by the amount of food that could be produced. This in turn has been limited by the amount of land under cultivation and the fertility of that land. Between 1700 and 1850 yields in the UK increased three fold with greater understanding of rotations, nitrogen fixing legumes and plant and animal breeding. In line with this increasing food production came an increase in population from 5.6 million in 1700 to 16 million by 1850. The energy for this increase in production, via photosynthesis, came from the sun.

After the second world war we had, what has been termed the second green revolution;the massive injection of soluble nitrogen fertilser, that along with further plant and animal breed improvements saw yields increase five fold. Likewise the world's population has increased, from 2.5 billion in 1950 to 7 billion today. The energy for this came not from the sun but from hydrocarbons (natural gas and oil) in the form of soluble fertilsers, pesticides, herbicides, fungicides and more centralised retail structures.

Today it takes 10 calories of hydrocarbons to produce1 calorie of food.

We, and the food we eat are the product of oil.

At the same time, through the use of such farming techniques we have seen the organic matter percentage of our soils plummet (organic matter is the soils ability to hold moisture and nutrients, it is the food for bacteria and other life forms that make the soil biologically active) to the extent that many soils would not be able to produce without the hydrocarbon inputs.

We are about to enter, (some would argue that we have already entered) peak oil. From now on the energy that has fueled our huge expansion is going to become more and more expensive. Methane burped and farted from cows isn't the problem, in fact, they could be part of the solution. However to get there we need to rethink our diet, and our population, not the cattle's.

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About the author

Stephen Merritt is a partner in The Welsh Poultry Centre and anaccredited advisor and board member of The Institute of Organic Training andAdvice and has spent over 30 years working in sustainable agriculture indeveloping countries, England and Wales. In the last 10 years Steve has specialised in free range and organicpoultry production and now offers on farm advice and training to this sector.