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Methane: the issue, the Science, the Solution. Roger Cohen Department of Animal & Poultry Science University of Saskatchewan. Focus on beef cattle. Rifkin (1992) - Beyond beef: The rise and fall of the cattle culture.

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methane the issue the science the solution
Methane: the issue, the Science, the Solution

Roger Cohen

Department of Animal & Poultry Science

University of Saskatchewan

focus on beef cattle
Focus on beef cattle

Rifkin (1992) - Beyond beef: The rise and fall of the cattle culture

“Cattle production and beef consumption now rank among the gravest threats to the future well-being of the earth and its human population”

slide3

Ryan Eliason (undated) - YES Handbook

“Cattle and other livestock account for twice the amount of pollutants as come from all U.S. industrial sources”

“Livestock production is perhaps the most massive force behind the destruction of our planet”

the earth s climate is changing
The earth’s climate is changing
  • Significant changes during 20th century

The cause is the enormous increase in anthropomorphic emission of greenhouse gases (GHG)

Carbon dioxide

Nitrous oxide

Methane

carbon dioxide
Carbon dioxide
  • Important sources are:

- Burning of fossil fuels (coal & petroleum)

- clearing and burning forests for crop and livestock production

slide6

Nitrous oxide

Important sources are: - Application of nitrogen fertilizer - Soil disturbance

Crop production most responsible Alleviated by - Deep banding - Zero till

Little use on pasture - legumes preferred

methane
Methane
  • By-product of anaerobic decomposition of organic matter
  • Important Non-anthropomorphic sources:

- wetlands - Forest fires

slide8

Important agricultural sources: Rice farming Ruminant livestock Manure (all species)

Other anthropomorphic sources: - Human waste Landfills, sewage, waste water - Fossil fuel industry Natural gas, petroleum processing, coal mining

global warming potential of ghg
Global Warming Potential of GHG

CO2CH4N2O

Radiative forcing relative to CO21 58 206

Lifetime (years)120 10 150

GWP in 100 years relative to CO2 1 21 290

Global Emissions (Gt/yr) a21.9 0.5 0.021

Global Emissions (GWP) b21.9 10.5 6.1

a 1 Gt = 1 billion tonnes

b Potential for a unit of gas for warming the world

slide12

Domestic livestock account for about 30% of anthropomorphic methane emissions in North America. Main sources are:

Eructated gas from ruminants (Cattle & sheep)

Manure

  • Are cattle a major cause of climate warming or can they be part of the solution?
recycling carbon through plants and animals is an important part of the solution to the ghg problem
Recycling carbon through plants and animals is an important part of the solution to the GHG problem
  • CO2 taken up by plants and stored in leaves, stems and roots as carbohydrates (cellulose, hemicellulose,lignin)

Cattle eat leaves and stems and return 25-60% of the Carbon to soil in feces

slide14

Incorporated into soil organic matter which enhances physical & chemical characteristics of the soil encouraging further plant growth

Most important role in recycling carbon belongs to the roots because they carry the carbon directly into the soil

two categories of plants used in agriculture
Two categories of plants used in agriculture
  • Perennial grasses and legumes used for ruminant livestock feed (73% of beef cattle feed)

Annual plants (cereal, oilseed & pulse crops etc.)

perennial plants
Perennial plants
  • Deep extensive root system

Dry matter below ground (roots carbon) = DM above ground (leaves + stems carbon)

About 50% of roots die and regenerate each year burying carbon deep in the soil

Channels from decayed roots improve moisture penetration and plant growth

slide17

Proper defoliation (grazing or mechanical) stimulates new growth of leaves, stems, roots

Incorrect defoliation (severe, wrong time) will weaken the plant which will eventually disappear

Careful management of defoliation is therefore critical to the mitigation of climate change

annual plants
Annual plants
  • Shallow roots
  • Above ground carbon >> below ground
  • Much of the carbon is removed from the system in the harvested material (grain)
  • Net depletion of soil organic matter (carbon) over time
carbon sequestration enhanced by
Carbon sequestration enhanced by:
  • Replacing degraded crop land with permanent pasture

Incorporating perennial forages (pasture/hay) into crop rotations

benefits other than removal of atmospheric carbon include
Benefits other than removal of atmospheric carbon include:
  • Reduced land degradation from wind and water erosion

Increased soil organic matter, fertility & water holding capacity

Soil salinity is checked

Deep water penetration is increased

slide21

It is the relative inefficiency of producing beef from pasture that makes it the most sustainable form of agricultural production

what about the methane emitted by cattle
What about the methane emitted by cattle?
  • The carbon in this source of methane is not “new” carbon - it is recycled carbon

Methane emitted by the coal and petroleum industries is “new” carbon

slide23

60 million bison roamed the northern great plains before settlement

Today there are only about 32 million cattle in the northern great plains region

carbon balance in a mixed native grass pasture grazed by 1 cow and calf on 2 ha 5 ac
Carbon balance in a mixed native grass pasture grazed by 1 cow and calf on 2 ha (5 ac)
  • CARBON SINKS:

Atmospheric CO2 taken up by pasture

Atmospheric CH4 absorbed by soil

Manure C incorporated into soil

C in pasture eaten by cow and calf

C passed from cow to calf in milk

C retained by calf as growth

slide25

CARBON SOURCES:

Respired CO2 from cow and calf

Eructated CO2 from cow and calf

Eructated CH4 from cow and calf

CH4 from manure of cow and calf

CO2 from manure of cow and calf

CH4 from decomposition of plant matter

slide26

Total carbon sinks = 20.73 kg C / d

  • Total carbon sources = 2.99 kg C / d

GWP of CO2 and CH4 = 1 and 21

Removal of GWP gases by cow & calf = 20.65 units / d

Emission of GWP gases by cow & calf = 6.46 unit / d

Net reduction in GWP = 14.19 units / d

slide27
In a single grazing season of 150 days this is a REMOVAL of 2,127.9 units of GWP gasesfrom the atmosphere
slide28

Assuming that the cow & calf emit a similar amount of CO2 and CH4 to the atmosphere for the remaining 215 days of the year and that there is no removal of CO2 and CH4 from the atmosphere by pasture and soil during winter:

Total sources of GWP gases = 2,359 units / year

Total sinks of GWP gases = 3,098 units / year

Net removal of GWP gases = 739 units / year

slide29

CONCLUSION

Grazing beef cattle are an integral part of climate change mitigation

slide30

Policy recommendations

Support for grazing management research & extension

Encourage correct management of all pasture lands through research and extension

Encourage return degraded crop land to permanent pasture

Encourage integration of perennial forage into cropping practices

Encourage more backgrounding and finishing of cattle on pasture