Which Plant-Based Milk is Best for the Environment?
This piece has been updated to reflect recent developments.
Americans are thirsting for plant-based milks.
2018 Nielsen data showed that, as sales of cow’s milk dropped six percent in the year leading up to June 2018, sales of plant-based milks went up nine percent and now make up 13 percent of overall “milk” sales.
Many companies making these “alt milks” (alternative milks) pitch their products as environmentally friendly. However, while relying less on foods sourced from animals is a good overall strategy to tread more lightly on Mother Earth, the truth about the sustainability of each product — including cow’s milk — is complicated by many factors.
When examining a product’s environmental footprint, variables like greenhouse gas (GHG) emissions, water use, land use, chemical runoff and soil degradation all have to be considered for each stage of production — from growing the raw ingredient to processing and transportation. (Not to mention how much waste, like leftover pulp, is produced and whether it’s reused. That varies from brand to brand so is hard to analyze overall.) Studies that take all of those into account and examine the trade-offs between different impacts are called life-cycle assessments (LCAs). “There are few plant-based milk life-cycle assessment studies,” explained Kiara Winans, a researcher in the Industrial Ecology Program at UC Davis.
- Life-Cycle Assessment
- A technique for assessing the potential environmental impacts associated with the creation of a product or service.
Winans and her colleague, Alissa Kendall, recently completed an LCA study of unsweetened almond milk that examined its impact on global warming and water use.
In order to accurately represent how products are made, LCAs need data directly from manufacturers, and companies often fund LCAs so they can make environmental claims about their products. That doesn’t mean the studies aren’t valid — LCAs have to conform to scientific standards to be published — but it’s important to consider the companies’ interest in positive results. Research might focus on parts of the product cycle that are low impact, or limit the analysis to impact categories where the product is likely to perform well.
Most LCAs evaluate only one company’s individual supply chain and process, which is a major limiting factor considering the diversity in the industry. Oatly, for example, makes oat milk using a completely different process than Pacific Foods does. And some companies are using totally new, proprietary processes that haven’t even existed long enough to study. Elmhurst Milked, for example, bucks the industry standard by using a process called HydroRelease that separates the components of the grain, nut or seed using water pressure rather than cutting or milling it and then allows them to recombine into a milk. This approach uses different inputs, changes the amount of raw materials in a product (i.e. more almonds in a container of almond milk compared to other brands) and significantly changes the nutritional value of the milk. So, if we’re talking about almond milk, for example, the various production processes used by both Elmhurst and Silk make comparing them very difficult.
This also brings up another factor: nutritional value. Which plant-based milk is the most nutritious might seem like a different question than which is the most sustainable, but the two are inextricably linked. Think about it: If you measured what it cost the planet to produce a cup of almond milk compared to a cup of soy milk and found they were comparable — does it change the formula if that cup of soy milk contains three times the protein and additional nutrients? If all of the water that went into making the almond milk was used to produce a food that’s barely more nutrient-dense than water, itself? Plant-based milks tend to be processed in ways that filter out many of the nutrients that all of the resources (water, energy, etc.) just went into producing.
“Judging from the very limited literature, plant milk substitutes have a lower impact on the climate and require less land to produce, but the issue is more complex as cow’s milk contains several key nutrients that are challenging to replace,” concluded researchers who conducted a recent review of the nutrient value of popular plant-based alternatives to cow’s milk.
To correct for this, some studies compare variables like water use and greenhouse gas emissions per grams of protein produced, not cup-to-cup. This variable will continue to evolve as technologies like those used by Oatly and Elmhurst Milked are expanded and more of the original nutrients are preserved in plant milks.
Finally, LCAs often include stages of the process beyond the production of the milk itself, like packaging, refrigeration, transportation, and recycling. These are important parts of the product’s life cycle and can make a big impact — Winans found that packaging emits far more greenhouse gases than actually making almond milk, for example — but not every study compares the same parts of the process.
With all of this in mind, we set out to compare the environmental impact of the most common plant-based milks (there are many others, of course, like cashew, rice and coconut) based on the best information available, focusing on the milks themselves. Packaging and shipping still make up a big part of any milk’s footprint, so don’t forget: No matter which you drink, you can cut out an entire chunk of the process that eats up resources and produces greenhouse gases by making your own plant-based milks at home, in a blender.
What You Need to Know About Each Plant-based Milk
Field to Factory
You could definitely argue that soy is the original plant-based milk. It’s been around much longer than most others and is more popular, thanks to a taste, texture and nutrition profile that’s generally the most similar to cow’s milk. Soybeans are legumes with roots in Asia, and they’re now grown all over the world, with a massive concentration of fields in the center of the US, the majority of which are used to produce animal feed. To be turned into milk, soybeans are usually pressed, the insoluble fiber is removed, and then other ingredients (like vitamins for fortification) are blended in.
Theoretically, soy milk should be one of the most sustainable choices. Studies show the greenhouse gas (GHG) emissions associated with its production are much lower than dairy and are about equal to almond and pea milk, and soybeans use less than a tenth of the water almonds do. When those numbers are adjusted to compare based on protein produced rather than liter by liter, soy milk beats almond by a landslide on both counts. Since soybeans are legumes, they also fix nitrogen in the soil, which reduces the need for nitrogen fertilizers.
Joseph Poore is a UK-based researcher who recently compiled and analyzed data on how food production impacts the environment from more than 38,000 farms in 119 countries. He says soy’s environmental Achilles heel is that growing the beans requires a lot of land compared to almonds or rice. We’re growing so much soy these days, in fact, that parts of the Amazon are being destroyed to plant it. Plus, in the US, especially, the vast majority of soybeans are grown in monocropped systems, and while they might not require as much nitrogen fertilizer, they do use phosphorous fertilizers, which are also connected to runoff that creates dead zones.
They’re also Roundup-ready, which means they’ve been genetically engineered to withstand heavy doses of the herbicide glyphosate, which pollutes ecosystems and is increasingly linked to cancer risk, especially among farmworkers. However, many of the big companies making soy milk use organic or non-GMO soybeans, and some, like Silk, specify that they source only from the US and Canada (so you don’t have to worry about rainforest destruction).
Soy can be a good choice, especially if you’re drinking milk for protein. Try to buy organic or non-GMO and/or check the source of the soybeans.
Field to Factory
Almonds grow on trees, and a lot of those trees are in California. In fact, the Sunshine State produces about 80 percent of the world’s almond supply, and production has increased over the past decade as more studies on almonds’ health benefits have been published increasing demand. To turn almonds into milk, the nuts are generally ground or pulverized, combined with water and filtered.
You’ve probably heard that growing almonds requires a lot of water, and that’s true. Nuts, in general, have a large water footprint compared to other plants, and the real problem is that these thirsty nuts are being grown in California, where serious drought conditions are an ongoing issue. A recent study calculated the total water footprint for one California almond averages 3.2 gallons. And while you could argue that almonds are worth the resources because they’re so nutrient-dense, the process of turning the nuts into milk eliminates most of the nutrients which all of that precious water just went into growing. There are also so few almonds in each carton, you’d get very few nutrients even if they were kept intact. Still, as Winan’s study notes, dairy milk consumes nearly twice as much water than an equivalent volume of almond milk.
The average total water footprint of one California almond.
Almonds don’t fare any worse than other alt milks on greenhouse gases or land use, but they guzzle up water in an area where that resource is incredibly scarce. And at the end of the day, you’re drinking a product that’s little more than water, anyway. Eat almonds in moderation, sure, but in terms of milks, there are more sustainable choices.
Field to Factory
Many companies make oat milk now, but Swedish brand Oatly has been doing it for almost 30 years, and it’s the most ubiquitous option. In the US, the company sources Canadian oats from Grain Millers. Oatly’s proprietary process involves combining whole oat groats with water and a natural enzyme blend. The enzyme breaks the oats down into liquid parts and Oatly then strains out insoluble fiber while leaving in the heart-healthy beta-glucans (a form of soluble fiber). Other companies use a mechanical breakdown process that involves blending and straining.
According to an LCA study that Oatly conducted in Sweden, the production of its oat milk results in 80 percent lower GHG emissions and 60 percent less energy use compared to cow’s milk. (The data used for cow’s milk was from Canadian dairy producers compiled in the Ecoinvent database. It’s important to note that it’s likely from conventional dairy producers and doesn’t take into account the potential environmental benefits of organic and/or grassfed dairy systems.) The study also found it uses about 80 percent less land. Of all of the plants turned into milk, oats generally use the least water. From a nutritional standpoint, oat milk tends to be much more nutrient-dense than almond but not as nutritious as soy, pea or hemp (but that varies depending on the brand). One issue is that a recent report showed oats are often contaminated with glyphosate at levels considered unsafe, because farmers spray Roundup on the crop right before harvest. Oatly, for one, doesn’t use organic oats in the US, but their supplier says it doesn’t allow growers to use glyphosate.
Oat milk gets high marks on most measures, if you buy from companies sourcing organic, or at least glyphosate-free oats. Its most impressive quality might be its taste and texture, which eaters (and baristas) tend to prefer over other alt milks. After all, no matter how eco-friendly a choice, a food can’t help the planet if no one is interested in choosing it.
Field to Factory
Pea milk is one of the newest entries into the category, and the most common brands are Ripple and Bolthouse Farms. Ripple sources split yellow peas from the Midwestern US and Canada, mills them into flour and then adds water plus a few additional ingredients like sunflower oil and vitamins.
Pea milk has a lot in common with soy, since soybeans and peas are both legumes. Peas fix nitrogen into the soil, reducing the need for nitrogen fertilizers, and require less water than many other crops. Unlike almonds, they’re also grown in areas where water is less scarce. In an LCA study done for Ripple (keep in mind the earlier caveat on industry-funded studies), researchers found producing Ripple pea milk results in comparable GHG emissions to soy (which are less than half that of cow’s milk). And like soy, the final product is rich in nutrients — particularly protein — so when compared to almond milk on a protein basis, it wins by a long shot on both water use and GHG emissions. Unlike soybeans, peas are not currently genetically modified for herbicide resistance. And Ripple, for one, claims that while its peas are not organic, growing them requires very few pesticides thanks to the dry, cool climates they’re grown in. Pea milks are still hard to find overall, but Suja does also make a certified-organic option.
Pea milk is comparable to soy in terms of a sustainable choice that is high in protein, and producing it might involve less pesticide use, depending on the brand and variety. One challenge is that the flavor is a little grassier than other plant-based milks, so those used to dairy may find it harder to adjust to the taste.
Field to Factory
Hemp milk has been available in the US for a while, but it had to be imported because of laws against growing hemp in the country. Since the 2018 farm bill recently legalized hemp farming, it’s likely the milk will gain some momentum. Hemp seeds are a valuable nutrition source, as they contain protein and healthy fats. They’re blended with water (and often a few additional ingredients) to create hemp milk.
Hemp has been an important crop throughout history because of its hardiness and versatility (for food, fiber and medicinal uses). While there hasn’t been a specific LCA study done to compare hemp milk to other milks, research shows hemp has many environmental benefits: it is effective for building soil health and requires very few pesticides because of its hardy nature. One study done by the European Environmental Agency compared the environmental effects of 16 common crops across factors like pesticides, erosion and water use; it ranked hemp in the top five. Hemp farming does require more water than oat, soy or pea (but still much less than almond or cow’s milk). Finally, hemp milk contains more protein than almond or oat but less than soy or pea; it also delivers healthy fats.
Hemp, as a crop, is well-known for its sustainability, and its seeds are a nutritious base for milk. More information is needed on hemp milk processing to fully compare its environmental impact to other plant-based milks.
Which Plant-based Milk is the Winner?
In the end, when you pit plant-based milks against each other, it’s probably pretty clear by now that calling one a “winner” isn’t quite possible. Too little research has been done so far, and too much of the research that does exist has been done by the plant-based milk producers themselves.
As interest in eating more sustainably grows, more research will emerge to help us understand the full environmental impact of all milks, from field to glass.