Key takeaways
- Cow's milk has a large footprint: about 3.15 kg of CO₂-equivalent, 8.95 m² of land and 628 liters of water per liter of milk.
- Brown Foods estimates its cell-based milk uses 82% less carbon, 90% less water and 95% less land. These are company estimates, not independent studies.
- No cows means no methane from digestion or manure, and far less farmland.
- The big unknown is energy: if bioreactors run on fossil power with pharma-grade inputs, the benefits could shrink or vanish.
The environmental case is one of the main reasons cell-based milk exists. Dairy farming has a large footprint, and growing milk without the cow could, in theory, eliminate much of it. But “in theory” is doing a lot of work. Here’s what we know.
How big is dairy’s footprint?
Livestock as a whole produces about 6.2 billion tonnes of CO₂-equivalent per year, roughly 12% of all human-caused greenhouse gas emissions, according to a 2023 report by the UN Food and Agriculture Organization. Cattle, both beef and dairy, account for about 62% of that. Slightly more than half of livestock emissions come as methane, a potent but short-lived greenhouse gas.
Per liter, cow’s milk compares like this with plant milks, based on the large 2018 study by Joseph Poore and Thomas Nemecek, as compiled by Our World in Data:
| Per liter of milk | Greenhouse gases (kg CO₂e) | Land use (m²) | Fresh water (liters) |
|---|---|---|---|
| Dairy milk | 3.15 | 8.95 | 628 |
| Rice milk | 1.18 | 0.34 | 270 |
| Soy milk | 0.98 | 0.66 | 28 |
| Oat milk | 0.90 | 0.76 | 48 |
| Almond milk | 0.70 | 0.50 | 371 |
Those figures are global averages built from data across more than 38,000 farms. Individual dairy farms vary enormously, but on average cow’s milk has the largest impact on every measure.
Where dairy’s impact comes from
- Enteric methane. Cows digest grass and feed by fermenting it in their rumen, releasing methane, mostly by burping.
- Manure. Stored manure releases methane and nitrous oxide, and runoff can pollute waterways with nitrogen and phosphorus.
- Feed and land. Growing feed and maintaining pasture takes a lot of land, and expanding pastureland has contributed to deforestation in some regions.
- Inefficiency. A cow uses most of the energy in its feed to live, move and keep warm, not to make milk.
Why cell-based milk could do better
Cell-based milk removes the cow from the equation. That eliminates enteric methane and manure entirely, and the land needed for pasture. The cells still need feeding, but they turn nutrients into milk without supporting a whole animal.
Brown Foods estimates its UnReal Milk has an 82% lower carbon footprint, uses 90% less water, and needs 95% less land than conventional cow’s milk.
Read the fine print: These are company estimates. As of this writing, we’re not aware of an independent, peer-reviewed life cycle assessment of commercial-scale cell-based milk. Treat headline percentages as goals, not results.
Why it might not live up to the hype
The closest comparison we have is cultivated meat, which uses similar cell-culture technology. A 2023 study by researchers at UC Davis (a preprint, not yet peer-reviewed at the time) found that cultivated meat made with today’s pharmaceutical-grade growth media could have a global warming impact 4 to 25 times higher than average retail beef. The culprit was the energy-intensive purification of growth media ingredients.
With food-grade media, the same study estimated cultivated meat could range from 80% lower to 26% higher than beef. In other words, the result depends heavily on how the industry scales.
Milk has one structural advantage over meat: the cells aren’t harvested. They keep producing milk continuously, so each batch of cells, and the media used to grow them, is spread over more product. That’s encouraging, but it hasn’t been demonstrated at scale.
The main factors that will decide cell-based milk’s real footprint:
- Energy source. Bioreactors need steady heating, cooling and pumping. Renewable power makes a large difference.
- Media inputs. Food-grade ingredients versus pharmaceutical-grade ones, and how efficiently they’re used.
- Productivity. How much milk each liter of bioreactor produces, and for how long.
How does it compare with plant milks?
Plant milks already deliver large reductions versus dairy, and they’re available today. Oat and soy milk, for example, cut emissions by roughly two-thirds or more and use a fraction of the land.
Cell-based milk’s environmental pitch is strongest for people who want real dairy and wouldn’t switch to plant milk anyway, and for uses like cheese, where plant alternatives struggle.
The verdict
Cell-based milk has the potential to be far better for the environment than conventional dairy, because it removes the biggest sources of dairy’s impact. Whether it actually is depends on decisions about energy and inputs that the industry hasn’t finished making. We’ll update this page as independent assessments are published.
Related reading: traditional dairy production, pros and cons and cell-based milk vs. plant milks.
Sources
- Our World in Data, Dairy vs. plant-based milk: what are the environmental impacts?, based on Poore & Nemecek (2018), Science
- UN FAO, New FAO report maps pathways towards lower livestock emissions, December 2023
- Brown Foods, “The World’s First Lab-Made Whole Cow Milk is Here”, February 25, 2025
- UC Davis, Lab-grown meat’s carbon footprint potentially worse than retail beef, May 2023
