Dairy Farming and the Environment: The Real Carbon Footprint of Milk and Cheese

The environmental footprint of dairy farming is significant, measurable, and more variable than simplified debates about animal products versus plant foods usually acknowledge. Dairy produces approximately 4% of global greenhouse gas emissions (Oxford University, 2018 Poore and Nemecek study), compared to 14.5% for all livestock together and approximately 26% for the entire food system. The 4% figure is an average that encompasses enormous variation: the most efficient New Zealand and Northern European grass-based dairy systems produce approximately 0.9 to 1.0 kg CO2-equivalent per litre of milk; the least efficient systems in Sub-Saharan Africa and parts of South Asia produce 6 to 9 kg CO2-equivalent per litre, a 6 to 10 fold difference. Discussions about dairy's environmental impact that ignore this variation are describing an average that does not exist as a real system anywhere.

Where Dairy's Emissions Come From

The greenhouse gas footprint of dairy comes from three main sources:

• Enteric fermentation (methane): Approximately 50% to 60% of total dairy emissions. Ruminants (cattle, sheep) digest plant matter through fermentation in their forestomachs, producing methane as a byproduct. Dairy cows produce approximately 100 to 120 kg of methane per year. Methane is a potent short-lived greenhouse gas (global warming potential approximately 28 times CO2 over 100 years); its short atmospheric lifetime (approximately 12 years versus CO2's centuries-long persistence) means its climate impact is more amenable to near-term reduction through herd management and dietary interventions than CO2 from fossil fuels.
• Feed production: Approximately 25% to 35% of dairy emissions. Growing the feed crops (maize, soy, cereals) fed to dairy cows requires land, water, fertiliser, and machinery with associated emissions. Grass-based systems have lower feed production emissions because pasture requires fewer inputs than cultivated crops; intensive grain-supplemented systems have higher feed footprints.
• Manure management: Approximately 15% to 20%. Slurry storage and application produces nitrous oxide (N2O, with a global warming potential approximately 265 times CO2) and methane. Anaerobic digesters (on-farm biogas plants that convert slurry to biogas) are increasingly adopted by larger dairy farms as both an emission reduction strategy and an energy generation system.

How Dairy Compares to Plant Milks

The 2018 Poore and Nemecek study in Science (covering 38,700 farms across 40 products in 119 countries) is the most comprehensive life-cycle analysis of food environmental footprints available. For milk and milk alternatives (per litre):

The greenhouse gas advantage of plant milks over dairy milk is approximately 3 to 4 times lower emissions. The water use comparison is more nuanced: almond milk has low GHG but high water use (most almond production is in drought-stressed California); soy has low water but a complex land use story (though the vast majority of soy globally is grown for animal feed, not directly for plant milk); oat milk has the best overall footprint across all three metrics.

Land Use: The More Complicated Argument

Dairy's high land use figure requires context. Most dairy land globally is permanent grassland that cannot be used for food crop production: steep slopes, thin soils, wet climates, or high altitudes unsuitable for arable farming. UK dairy farming in particular is largely based on permanent pastures in the uplands of Wales, Cumbria, and Scotland that have no viable alternative agricultural use. Replacing dairy with plant-based alternatives on land capable of arable production reduces the land requirement; on permanent grassland in regions like the UK, dairy cattle may represent the most productive use of land that would otherwise produce no food.

Permanent grassland also stores carbon in the soil. Well-managed UK pastures sequester approximately 0.4 to 1.5 tonnes of carbon per hectare per year; some studies suggest that high-quality permanent pasture under rotational grazing can sequester enough carbon to partially or substantially offset the methane emissions from grazing cattle. The evidence for this is actively researched and contested; it does not apply to degraded pastures or heavily supplementary-fed systems.

Progress and Prospects

The UK dairy industry has reduced its carbon footprint by approximately 25% per litre of milk produced over the past 20 years (NFU, 2021), driven by improved herd genetics (producing more milk per cow), feed efficiency improvements, and manure management upgrades. The UK dairy industry's net zero commitment (the NFU's target of net zero greenhouse gas emissions for the UK farming sector by 2040) encompasses dairy and involves a combination of methane-reducing feed additives (Bovaer, a synthetic 3-nitrooxypropanol compound, reduces enteric methane by 25% to 30% when added to feed), on-farm renewable energy, improved soil management, and anaerobic digestion.

Related: Organic Dairy Farming: What It Means for Nutrition and Animal Welfare | Plant-Based Milk Comparison: Which Is Best for the Environment?