Something of a wet blanket was thrown over the World Milk Day celebrations last week in the form of a story in The Guardian and on the ABC about dairy’s carbon footprint.
Avoiding meat and dairy products is the single biggest way to reduce your environmental impact on the planet, according to the scientists behind the most comprehensive analysis to date of the damage farming does to the planet.
– The Guardian, June 1 2018
The story was based on a study published in the journal Science that was based on almost 40,000 farms in 119 countries.
Being something of a “greenie” myself, I know how much emissions vary depending on how we farm and that was reinforced by a chart in The Guardian’s story. The lightest cheese footprint really is quite light! But where does Aussie dairy sit in the spectrum?
To learn more, I asked Catherine Phelps of Dairy Australia for answers. Thank you, Cathy, for these incredibly comprehensive answers!
MMM: How much does the farm gate carbon footprint for dairy vary around the world?
CP: There is a wide variation in the carbon footprint for dairy.
A 2010 study by the Food and Agriculture Organisation on Greenhouse Gas Emissions (GHG) from the Dairy Sector (2010) reported the highest emissions of about 7.5kg carbon dioxide equivalent per kg of fat and protein corrected milk (FPCM) for sub-Saharan Africa.
The developed regions of the world had the lowest footprints of 1 – 2 kg of carbon dioxide equivalent per kg of FPCM. Asia, North Africa and South America have intermediate levels of emissions.
The Australian dairy industry 2010 carbon footprint study of farm gate GHG emissions reported the average GHG emissions to be 1.1kg of carbon dioxide per kg of FPCM. Per unit of production Australian dairy producers have one of the lowest carbon footprints in the world.
MMM: Why is there such a variation?
CP: Differences in carbon footprints are usually related to the efficiency of the production system, cow genotypes and the quality of the forage.
In arid or humid zones where producers are reliant on native grassland, the quality of the feed is poor and milk production per cow is low. The genotype of dairy breeds best suited to poor quality feed and/or high temperature and humidity is often adversely correlated with milk production efficiency.
The majority of GHG emissions from Australian dairy production systems are methane from enteric fermentation (57%); followed by methane and nitrous oxide from urine and dung (18%).
MMM: What have Australian dairy farmers done to reduce their carbon footprint and how has it changed over time?
CP: Between 1980 and 2010, the Australian dairy industry reduced its carbon footprint per kg of FPCM by 30%.
This reduction is due to improved production efficiencies, examples being better quality pasture and selection of higher genetic merit cows. Enteric methane emissions represent energy losses from the digestive process. Improving feed quality, breeding animals with increased feed conversion efficiency and use of specialist feed additives reduces the amount of energy lost as enteric methane.
Increased adoption of good practice manure and nitrogen fertiliser management is also contributing to the lower carbon footprint.
MMM: Does combining animal farming and cropping have any environmental benefits?
CP: This is not an easy question to answer. The practices implemented by an individual producer are often more important than their type of farming system with respect to environmental impacts.
The argument for mixed farming over specialised livestock or cropping systems is usually based on the assumption that animals can utilise cropping waste, or take advantage of grazing cereals with the outcome being greater productivity per unit of land. In addition, animals contribute nutrients to the soil through manure and pasture can act as a disease break crop and/or soil conditioner.
Whether a mixed farming system is more environmentally beneficial will depend on the management practices being implemented. For example, a zero tillage cropping system may have less impact on water quality and soil health than a mixed farming system with a high proportion of conventional cropping.
A different approach is to identify practices which boost productivity whilst reducing environmental impacts. Some of these will be common across farming systems, others will be relevant to a particular system and its location. For example using a nutrient management plan to inform fertiliser/manure applications and identify and remediate soil constraints will improve soil health and farm profit whilst reducing the risk of nutrient loss regardless of the farming system.
MMM: If Australians adopted a vegan diet, what difference would that make to the area of land needed to sustain us?
CP: Recent research based on the Dutch diet reported carbon emissions could be reduced by approximately 2.9 tonnes/person by eating vegan. However the nutrients lost by avoided animal products would need to be compensated by plant-based products. To obtain the nutrients provided by dairy an individual must eat more fruit and vegetables than the recommended daily portions.
The same research estimated the amount of land needed to produce the extra plant food is equal to the land used by dairy. The carbon emissions from the extra food were similar to dairy. Similar research has not been conducted in Australia.
A US study found the removal of animals from the agricultural system resulted in diets with excess energy that were deficient in essential nutrients. There was potentially a decrease in the area of land required, however to support the nutritional needs of the US population nutritional supplements would be required.
The outcome determined that is a challenge to scale up plant-based diets to meet the nutrient needs of whole populations, due to land availability, soil type and climate.
MMM: Aside from eliminating animal foods, what are the implications of a vegan diet and lifestyle?
CP: When considering the environmental impact of various agricultural products it is important to consider the full nutritional value delivered by different foods. Multiple research papers have found that whilst it is possible to meet essential nutrient requirements through vegan diets this can be a challenge in reality.
Without careful balancing such diets are likely to be deficient in various micro-nutrients and fatty acids including calcium, vitamin A, Vitamin B12 and vitamin D. These nutrient deficiencies can be difficult to manage at a population level. Products like dairy are nutrient dense and an excellent source of many essential micro-nutrients and fatty acids.
There are alternative lifestyle options for reducing individual greenhouse gas emissions that don’t involve a significant change in diet.
For example driving a smaller car, reducing air travel, or sequestering carbon by planting more trees. A passenger on a return flight from Melbourne to London return will be responsible for producing approximately 11.2 tonnes of carbon emissions (https://www.treesforlife.org.au/carbon/calculate-your-impact/ready-use-calculations).
Planting five trees will sequester one tonne of carbon.