Oat milk has the smallest overall environmental footprint of the widely available plant-based milks. It produces the least greenhouse gas emissions, uses very little water, and requires modest amounts of land. But the full picture is more nuanced: each plant milk has strengths and trade-offs depending on whether you care most about carbon, water, land, or biodiversity.
Every plant-based milk significantly outperforms dairy on most environmental measures. The real differences show up when you compare them against each other.
How Plant Milks Compare to Dairy
Dairy milk produces roughly 2.2 kg of CO2 equivalent per liter from farm to retail in Europe, which is among the lowest dairy footprints globally. Plant milks cut that dramatically. Oat milk’s carbon footprint is just 29% of dairy’s, soy comes in at 38%, and rice at 41%. So even the least climate-friendly plant milk still generates less than half the emissions of cow’s milk.
Land use follows a similar pattern. Rice, oat, and soy milks use only 16%, 18%, and 23% of the land dairy requires, respectively. That’s because dairy cattle need pasture and feed crops, which together consume enormous amounts of space.
Water is where the comparison gets interesting. Oat milk uses just 1.3% of dairy’s water, and soy milk uses a remarkably low 0.5%. Rice milk, however, flips the script entirely: it requires 2.36 times more water than dairy milk, making it the most water-intensive option by a wide margin.
Oat Milk: Lowest Carbon, Low Water
Oat milk leads on climate impact, producing only about 29% of the greenhouse gases that dairy does. It also sips water rather than gulping it, using a tiny fraction of what dairy or rice milk demands. Oats grow well in cooler climates like Scandinavia, Canada, and the northern United States, which means production doesn’t typically drive tropical deforestation.
The main environmental concern with oats is pesticide use. Glyphosate, a common herbicide, is frequently applied to conventional oat crops. Testing has found residues in oat products, though all reported levels fall well below the U.S. EPA tolerance of 30 mg/kg for oats. Choosing organic oat milk sidesteps this issue, since organic farming prohibits glyphosate. Oats also require synthetic nitrogen fertilizer, unlike legume crops that can produce their own.
Soy Milk: Best on Water, Good on Carbon
Soy milk uses the least water of any plant milk studied, at just 0.5% of dairy’s water footprint. Its carbon emissions are low too, at 38% of dairy’s. There’s a bonus on the farming side: soybeans are legumes, meaning they host bacteria in their roots that pull nitrogen directly from the air. This natural process, called nitrogen fixation, supplies up to 50% of the plant’s nitrogen needs, reducing the synthetic fertilizer required compared to crops like oats or rice.
The word “soy” often triggers concerns about deforestation, and those concerns are real but misdirected when it comes to soy milk. Nearly 80% of the world’s soybean crop is fed to livestock for beef, chicken, egg, and dairy production. The soy in your carton of soy milk represents a sliver of global demand. Forests and savannas in South America are being converted to farmland for soy, but the primary driver is animal feed, not plant-based milk. Buying soy milk made from beans grown in North America or Europe further reduces any link to tropical deforestation.
Almond Milk: The Water Problem
Almond milk is one of the most popular plant milks in the U.S., but it carries a significant environmental burden that the others don’t. About 80% of the world’s almonds are grown in California, a state that faces chronic drought. Almond trees are permanent crops that need water year-round, unlike seasonal grains that can be rotated or fallowed during dry years.
The other major issue is pollinators. California’s almond orchards rent upwards of 1.5 million honeybee colonies each year, at a cost of around $300 million, trucked in from across the country to pollinate the February bloom. Research from Ohio State University found that bees and larvae were dying during pollination season. In 2014, roughly 80,000 colonies (about 5% of those brought in) experienced significant adult bee deaths or dead and deformed brood. The culprit turned out to be combinations of insecticides and fungicides sprayed on the orchards. While each chemical was individually deemed “bee-safe,” mixtures decreased larval survival by more than 60% in the most extreme cases. As one researcher put it, spraying insecticide while 80% of the nation’s honeybees are sitting in your orchard doesn’t make sense.
Almond milk’s carbon and land footprints are relatively modest, but the water and pollinator costs make it harder to recommend as the greenest choice.
Rice Milk: High Water, High Emissions
Rice milk consistently ranks as the least environmentally friendly plant-based option. Its carbon footprint, while still lower than dairy’s, is the highest among plant milks at 41% of dairy’s emissions. The main reason is how rice is grown: flooded paddies create oxygen-free conditions where microbes produce methane, a potent greenhouse gas.
The water situation is even worse. Rice milk requires 2.36 times more water than dairy milk, making it the only plant milk that actually exceeds dairy’s water footprint. If you live in a water-stressed region or care about water conservation, rice milk is the weakest choice by a significant margin.
Coconut Milk: Low Carbon, Ecological Concerns
Coconut milk generally has a low carbon footprint, but the full environmental picture is less clear-cut. Coconut palms grow exclusively in tropical regions, often in biodiversity hotspots across Southeast Asia, the Pacific Islands, and parts of Africa. When new plantations replace existing forest, emissions can increase by 0.3 to 0.6 kg of CO2 equivalent per liter depending on what the land was before. The impact on local ecosystems, including coastal habitats, is an active concern in life-cycle assessments of coconut products.
Because coconut farming is concentrated in developing countries with less regulated supply chains, the ecological cost can vary widely depending on sourcing practices. Certifications like Fair Trade or Rainforest Alliance can signal more responsible production, though they don’t eliminate all concerns.
What to Pick Based on Your Priority
- Lowest overall footprint: Oat milk wins across carbon emissions, water use, and land use. It’s the safest all-around choice.
- Lowest water use: Soy milk edges out oat milk, using just 0.5% of dairy’s water compared to oat’s 1.3%.
- Lowest carbon emissions: Oat milk, at 29% of dairy’s carbon footprint.
- Best for soil health: Soy milk, because soybeans fix their own nitrogen and need less synthetic fertilizer.
- Worst for water: Rice milk, the only plant milk that uses more water than dairy.
- Worst for pollinators: Almond milk, due to industrial beekeeping practices tied to California orchards.
Geography matters too. An oat milk made from oats grown locally in northern Europe or Canada will have a smaller transport footprint than one shipped across the globe. The same logic applies to any plant milk. Where and how the crop is grown can shift the math considerably, so checking where a brand sources its ingredients adds another layer of informed choosing.