Soy milk has a significantly smaller environmental footprint than dairy milk by nearly every measure, though it’s not impact-free. Producing one liter of soy milk requires about 297 liters of water, roughly a third of what cow’s milk demands. Its greenhouse gas emissions and land use are also far lower than dairy. But the full picture depends on where the soy is grown, how it’s farmed, and what you’re comparing it to.
How Soy Milk Compares to Dairy
The environmental case for soy milk over cow’s milk is strong across the board. Dairy milk typically requires around 600 to 1,000 liters of water per liter produced, depending on the region and farming system. Soy milk’s 297-liter water footprint, measured in a Belgian production study by UNESCO’s water research institute, is a fraction of that. Nearly all of soy milk’s water use (over 99%) happens in the supply chain, mainly in growing the soybeans themselves rather than in processing.
On carbon emissions, soy milk produces roughly 0.9 kilograms of CO₂ equivalent per liter, compared to about 3.2 kg for dairy. Land use follows a similar pattern: soy milk needs less than a square meter of land per liter, while dairy requires several times more. If your primary concern is choosing a lower-impact option over cow’s milk, soy milk delivers on that.
The Deforestation Question
This is where most people’s concern about soy and the environment actually lives, and it’s worth understanding the full picture. Soy farming has been a major driver of deforestation in South America, particularly in the Amazon rainforest and Brazil’s Cerrado savanna. But the vast majority of that soy isn’t going into your carton of soy milk. Nearly 80% of the world’s soybean crop is fed to livestock, primarily for beef, chicken, egg, and dairy production. The soy that ends up in tofu, soy milk, and other human foods represents a small slice of global production.
That distinction matters. When forests are cleared for soy in South America, the economic force behind that clearing is overwhelmingly animal agriculture, not plant-based food manufacturers. Research from the European Forest Institute found that just 2% of private properties account for 60% of illegal deforestation in the Amazon and Cerrado, pointing to concentrated, large-scale operations rather than broad industry-wide practices.
Geography also plays a role in what you’re actually buying. Most soy milk sold in North America and Europe sources beans domestically or from certified supply chains rather than from newly deforested land. U.S.-grown soybeans, for example, come from established farmland in the Midwest. Some international brands are now adopting sustainability certification programs that require verified sourcing from countries with stronger land-use protections.
Emissions From Soy Farming Itself
Even on established farmland, growing soybeans has environmental costs that scientists are only recently quantifying. Iowa State University researchers found that in the typical corn-soybean rotation used across the U.S. Midwest, 40% of nitrous oxide emissions occur during the soybean year. That’s surprisingly high, because soybean fields generally aren’t treated with nitrogen fertilizer. Soybeans fix their own nitrogen from the air, so farmers assumed the crop’s emissions were minimal.
The real culprit is bare soil. After corn is harvested in the fall, fields sit exposed through winter and early spring. When soil microbes break down organic matter during warmer, wetter months, they release nitrogen as nitrous oxide, a greenhouse gas roughly 300 times more potent than CO₂ over a century. As the Iowa State team put it, “Half the year, we have bare soil,” and that uncovered ground is responsible for a large share of emissions nobody had been managing.
The good news is that solutions exist. Planting winter cover crops like oats or rye between harvest and the next planting season keeps living roots in the ground, absorbing that nitrogen before it escapes. Combined with earlier spring planting of extended-growth soybean varieties, this approach could cut soybean-year emissions by about 33%. These practices aren’t yet widespread, but they’re gaining traction as farmers learn that soybean emissions are a bigger piece of the puzzle than previously thought.
How Soy Milk Stacks Up Against Other Plant Milks
Among plant-based milks, soy milk sits in the middle of the environmental spectrum. Oat milk uses slightly less water in most estimates and produces comparable emissions. Almond milk, by contrast, is far more water-intensive, requiring over 370 liters of water per liter, and most almonds come from drought-stressed California. Rice milk has the highest emissions of the plant milks due to methane released from flooded rice paddies. Coconut milk has a low carbon footprint but raises concerns about fair labor practices and monoculture farming in tropical regions.
Soy milk does have one nutritional edge that indirectly affects its environmental profile: it’s the closest plant milk to dairy in protein content. Since protein delivery per liter of water or per unit of emissions is one way researchers measure efficiency, soy milk’s roughly 7 grams of protein per cup makes it one of the most resource-efficient ways to get plant-based protein from a beverage.
What Actually Determines Your Carton’s Impact
The environmental footprint of any specific carton of soy milk depends on a few practical factors. Where the soybeans were grown matters most. Domestically sourced soy from established farmland in the U.S., Canada, or Europe carries a very different footprint than soy linked to recent land conversion in South America. Organic soy avoids synthetic pesticides but doesn’t necessarily use less land or water.
Packaging also plays a small but real role. Shelf-stable cartons (the kind that don’t need refrigeration until opened) generally have a lower transport footprint than refrigerated soy milk, which requires cold-chain shipping. And the simple math of food waste applies: a carton that gets used fully has half the per-serving footprint of one that gets poured down the drain when it expires.
If you’re choosing soy milk as a swap for dairy, you’re making a measurably lower-impact choice on water, land, and emissions. If you’re comparing it against other plant milks, the differences are real but smaller, and soy milk holds up well, particularly when you factor in its protein content. The biggest environmental problems associated with soy as a crop are driven by animal feed demand, not by the relatively small share that ends up in plant-based foods.