Why does organic milk have a higher carbon footprint?
The Oxford English Dictionary defines a carbon footprint as “the total amount of greenhouse gases produced to directly and indirectly support human activities, usually expressed in equivalent tons of carbon dioxide (CO2).”
It takes 80% more land to produce one unit of milk than conventional production does. Whilst energy is saved by the avoidance of synthetic fertiliser applications, this is actually being offset by the significantly lower yields and greater mechanical field inputs. These low yields create a negative environmental knock-on effect because an organic dairy farm needs a larger area to produce less milk than a conventional farm.
Higher on-farm energy consumption.
The energy consumption per functional unit in the on-farm process is around 20% higher on an organic model than it is on a conventional one.
On-farm primary energy use in the organic system is 15.8% 5 higher than the conventional system, while organic milk required 33.9% 6 more fuel per thousand litres of milk.
Furthermore, the organic systems requires approximately a third more man hours than conventional systems. The longer man hours include machinery hours and therefore creating a greater consumption of fossil fuels, in the form of diesel and electricity, increasing organic milk’s carbon footprint.
Synthetic vs Organic Fertilizer.
The organic system can require the spreading of up to 20 tonnes/ha of manure, and the average conventional farm applies around 1100 kg/ha of synthetic fertiliser That is around 20 times the weight difference in transport and management every year. This figure is staggering when you consider the difference in power and machinery hours needed to load, transport and spread up to 20 t/ha of manure compared to a meagre 1.1 t/ha of synthetic fertiliser, having implications on fossil fuel consumption and the carbon footprint. Furthermore, in many cases when an organic farm has insufficient solid manure from its own cows it is actually forced to import organic manure from other organic farms.
Higher methane emissions.
Methane gas is twenty three times more potent than carbon dioxide. It is estimated that cows in the UK alone produce up to 500 litres, per cow, of methane every day, a figure so high that they account for 3% of the UK’s total greenhouse gas emissions.
Organic milk’s methane contribution is 18% higher than conventional milk. In the UK showed the figure to be 70% methane in the organic system, compared to 52% on the conventional system.
The reason for the higher production of Methane is that organic cows eat more roughage, this takes to longer to digest than the diet of an animal in an intensive system. Grass is rich in cellulose and other tough components; symbiotic bacteria living in her gut help break down this tough food. Unfortunately, these bacteria emit huge amount of methane while doing this job. Since and organic cow needs more time to digest, she produces more methane than a conventional cow.
Supplementary Organic Cattle Feed.
A commercial dairy cow cannot exist solely on a grass fed diet. The additional protein requirements for organic dairy cows create a large carbon footprint in themselves, as the produce cannot be grown in temperate/cool climates. The standards set by the UK’s organic bodies forbid the use of GMO feeds which would lower the amount of carbon used. Something that is often overlooked is that Soya meal, a key protein rich ingredient is sourced from farms in Asia, South America and the US. These imports are fuelling slash and burn techniques and further deforestation in areas of South America. This shatters the food mile argument from much further down the supply chain, before the manufacturing process of feeds begins and even before feed is synthesised into milk. Whilst Soya meal is not present in all cattle feeds, the environmental impact of long distance goods importation must not be underestimated.
Does the carbon footprint of organic milk production negate its environmental benefits?
Henry J.W. Robertson Oxford Brookes University
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