Increased Greenhouse Gas Emissions
  • Agriculture accounts for about one-fifth of the projected anthropogenic greenhouse effect - producing about 50 and 70%, respectively, of overall anthropogenic CH4 and N2O emissions. Agricultural activities (not including forest conversion and biomass burning) are estimated to account for approximately 5% of anthropogenic emissions of CO2.
  • Methane (CH4)

    Methane is a greenhouse gas, it affects the ozone layer in the atmosphere and it contributes to global warming or global climatic change. The largest agricultural sources of CH4 are managed ruminant animals and rice production.

    Methane is emitted from 3 sources within livestock production systems:

    Methane emissions from 
    the digestive process:
    Methane emissions from 
    anaerobic decomposition of manure:
    Methane emissions from 
    anaerobic decomposition of waste water:
    The digestive process of ruminants is an important source of methane. The quantity of methane produced depends largely on the crude fibre percentage of the feed - the higher the crude fibre content, the higher the methane emission as a percentage of the gross energy intake. 

    However, as low crude fibre rations are almost always combined with a higher total energy intake, the effect per animal is small. 

    Methane emission levels from the digestive process in pigs and poultry are low.

    Manure from all types of animals can produce methane. 

    High levels of methane per unit of product are produced when manure is stored under anaerobic conditions. Only facilities that manage manure as a liquid or slurry are capable of sustaining anaerobic conditions. These facilities include lagoons, pits and tanks. 

    Liquid manure management facilities are most commonly used when there is a large concentration of animals at a single facility, such as at farms in the industrial animal production system.

    Manure that is handled in dry form, spread on fields, dried for fuel, or deposited by grazing animals does not produce any appreciable amount of methane. 

    Disposal of untreated wastewater can cause anaerobic decomposition of the organic waste that will result in the emission of methane.
    Nitrous Oxide (N2O)

    This is the most aggressive greenhouse gas (320 times more aggressive than CO2) contributing to global warming. Nitrous oxide is produced as part of the denitrification process of manure. This occurs both during storage and when manure has been applied to the land.

    Carbon Dioxide (CO2)

    The principal anthropogenic source of Carbon Dioxide is the combustion of fossil fuels, which accounts for about three-quarters of total anthropogenic world-wide emissions of carbon. Biomass burning is also an important contributor.  Industrial animal production, through its reliance on mechanisation both at the site of animal production and at the site of animal feed cultivation contributes to production of CO2 largely through the use of fossil fuels.

    See Also:

    Increased Use of Fossil Fuel for Transport and Processing of Concentrates

    Increased Use of Fossil Fuel for Inputs (Mechanization, Fertilizers and Agro-chemicals)

    Greenhouse Gas Emissions, Fossil Fuels and Taxes

    OECD. (1997) CO2 Emissions from Road Vehicles. Expert group on the UN Framework Convention on Climate Change. Working Paper 1. Click here to view this document in Acrobat format (881KB) 
    NASA, 1999. Biomass burning and global change.

    Levine, J.S. 1994. Biomass burning and the production of greenhosue gases. In: Zepp, R.G. (ed) 1994. Climate Biosphere Interaction: Biogenic Emissions and Environmental Effects of Climate Change. John Wiley and Sons. ISBN 0-471-58943-3.

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