Greenhouse gas emissions

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The reduction of greenhouse gas emissions was one of the principal commitments made at the recent IDF World Dairy Summit (Begg 2005). Life cycle studies on greenhouse gas emissions for market milk in Sweden and Australia show that the bulk of greenhouse emissions occur at the farm, 87% in Sweden and 70% in Australia (Nicol 2004; Svenskmjolk 2004) (see Table 14.9). Farm emissions comprise methane from cows and nitrogen

Table 14.7 Energy consumption for various dairy products (GJ/tonne end product). Source: Joyce and Burgi (1993)

Product

Electricity consumption (GJ/tonne)

Fuel consumption (GJ/tonne)

Market milk

0.20

0.46

Cheese

0.76

4.34

Milk powder

1.43

20.60

Butter

0.71

3.53

Table 14.8 Energy consumption for different evaporation and drying systems (GJ/tonne product). Source: Joyce and Burgi (1993)

Type of evaporation and drying system Energy consumption (GJ/tonne)

5-effect evap. and 2-stage drier 13-15

3-effect evap. and 1-stage drier 22-28

2-effect evap. and 1-stage drier 40-50

Table 14.9 Proportion of life cycle greenhouse gas emission for market milk produced in Australia (Nicol 2004) and Sweden (Svenskmjolk 2004)

Activity

Greenhouse gas Australia

emissions Sweden

Farm

70%

87%

Raw milk transport

4%

1%

Manufacturing

5%

2%

Packaging

4%

4%

Transport to market

2%

2%

Market/consumer

15%

5%

oxide from effluent and fertiliser denitrification (Nicol 2004). Methane is formed when the cow ruminates and the feed is broken down in the first stomach and intestines. In one year, a cow produces 120-130 kg of methane through this natural process (Svenskmjolk 2004). The productivity of the cow has a direct impact on the relative contribution of greenhouse gas emissions to overall life cycle emissions (Svenskmjolk 2004). A high-yielding cow releases slightly more methane but, calculated per kilogramme of milk, the high-yield cow releases less greenhouse gases. Future reductions in greenhouse gases can be achieved by increasing cow productivity with improvements in nutrition, pastoral management and genetics.

Greenhouse gases are also released in other parts of the life cycle of milk. Transport is the next greatest contributor, primarily due to the use of the fossil fuels used to transport the raw milk to the factory then distribute it to market and the consumer, especially in Australia where greater distances are involved. Packaging also represents 4% of the greenhouse gases, with methane emissions from the disposal of milk packages representing approximately 30%, while 70% are emissions of carbon dioxide (Svenskmjolk 2004). The remaining greenhouse gas emissions arise from manufacturing processes, which are relatively low for market milk but increase considerably with energy-intensive processing such as evaporation and drying.

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