What Is Anaerobic Coffee? Process, Flavor and Labels Explained
Anaerobic coffee is coffee fermented in a sealed, low-oxygen container before drying, and this lesson explains how it's made, how it tastes, and how to read the labels. About a 9-minute read.
Anaerobic coffee is coffee that ferments inside a sealed tank or bag with little or no oxygen before it is dried. As the fruit ferments, carbon dioxide builds up and pushes oxygen out, which changes which microbes do the work. The result is usually a more intense cup with fuller body, ripe or boozy fruit, and sometimes a tangy, yogurt-like edge. Labels like anaerobic natural and anaerobic washed tell you what happened next.
You picked up a bag that says "anaerobic natural" or "double anaerobic" and the tasting notes read like a dessert menu. The label sounds like lab work, and the price is often higher than the bag next to it. Here is what the word means and whether the coffee is for you.
Anaerobic processing is one of a family of newer fermentation methods that producers use to push flavor in a particular direction. In our own catalog, about 1 in 5 coffees that publish a process use an experimental method like this one (see Lesson 05: coffee by the numbers). So you will see the word more and more.
This lesson covers what happens inside the tank, what it does to flavor, what the add-on labels mean, and a few anaerobic coffees from our catalog worth a look. If you are new to processing in general, Lesson 02 on origin, processing and roast is a good primer.
What does anaerobic mean in coffee?
In coffee, anaerobic means the coffee ferments without oxygen. Soon after picking, producers seal the cherries or beans in a tank, barrel or bag. Fermentation releases carbon dioxide, which fills the container and forces oxygen out. One-way valves let extra gas escape while keeping air from getting back in.
All coffee ferments a little after harvest, usually open to the air. Closing the lid matters because oxygen decides which microbes thrive. Coffee Review's 2021 report on anaerobic coffees explains that without oxygen, yeasts are held back and bacteria become more active. Those bacteria make lactic acid, the same acid behind the tang in yogurt and kefir. Yeast-led fermentation tends toward fruit and alcohol notes instead.
According to the same report, coffee usually stays sealed for about one to six days. A longer ferment gives a stronger anaerobic effect. After the tank, the coffee is dried like any other coffee, and how it is dried gives us the second half of the label.
How is anaerobic coffee made?
Anaerobic coffee is made in three broad steps: seal the coffee in a container, let it ferment for a set time while carbon dioxide displaces the oxygen, then dry it. The equipment ranges from cheap plastic barrels to stainless steel tanks that control temperature, pressure and pH, and that control shapes the final flavor.
- Coffee cherries (or beans with some fruit left on) go into a sealed container shortly after harvest.
- Fermentation produces carbon dioxide. Some producers also inject carbon dioxide to push oxygen out faster.
- Producers watch time and temperature, then open the tank after hours or days.
- The coffee is dried, either still in the fruit or after the fruit is removed.
The idea comes from wine. Sprudge credits 2015 World Barista Champion Sasa Sestic with bringing it to coffee after he worked with a winemaker in Canberra, Australia. At that competition he used a coffee processed by carbonic maceration, a version of anaerobic fermentation where carbon dioxide is pumped in to replace the oxygen.
Temperature is one of the biggest levers. Nicaraguan producer Erwin Mierisch told Sprudge that warmer ferments produce more intense brown-spice notes like cinnamon and clove, while cooler ferments give cleaner, more vibrant acidity. His farm ferments at 8 to 10°C (about 46 to 50°F).
The method is also risky. A tank that runs too long or too warm can ruin a whole lot. Mierisch keeps his anaerobic lots to no more than 10 bags of 69 kg each for that reason. Small lots, extra labor and the chance of loss are part of why these coffees often cost more.
What does anaerobic coffee taste like?
Anaerobic coffee usually tastes more intense than a classic washed coffee, with fuller body, more sweetness and ripe, sometimes boozy fruit. Many lots carry a tangy, lactic edge. The flavors can be polarizing: some cups read as tropical fruit and chocolate, while others lean toward cinnamon, wine or even cheese.
When Coffee Review cupped 43 anaerobic coffees for its 2021 report, it found common notes like fruit, chocolate, cedar and flowers. It also found less common ones like soft cheese, kefir, tobacco and mushroom. Overall the samples showed greater intensity and fuller body. Nineteen of the 43 scored 93 points or higher.
You can see the pattern in the tasting notes roasters publish for anaerobic coffees in our catalog. The roasters list notes like cherry cordial and marzipan, blueberry and fig, cinnamon roll and baked apple, and "winey." These flavors show most clearly at lighter roasts. If tasting-note language is new to you, Lesson 01 on tasting notes explains how to read it.
One caution from roasters themselves: too much fermentation can bury a coffee's own character. In Coffee Review's report, one roaster compared heavy-handed fermentation to a dark roast, since both can mask what the farm and variety bring to the cup. A well-made anaerobic coffee should still taste like coffee, with the fermentation adding to it.
What do anaerobic natural, double anaerobic and co-ferment mean?
These labels describe what happened before and after the sealed ferment. Anaerobic natural means the beans dried inside the fruit afterward. Anaerobic washed means the fruit was removed before drying. Double anaerobic has no standard definition. Co-ferment means something extra, such as fruit or yeast, went into the tank with the coffee.
| Label | What happens | What to expect |
|---|---|---|
| Anaerobic natural | Whole cherries ferment sealed, then dry with the fruit on | The most fruit-forward and intense style; jammy, boozy notes are common |
| Anaerobic washed | Sealed ferment, then fruit is removed before drying | Cleaner and brighter than an anaerobic natural, still with extra sweetness |
| Anaerobic honey | Sealed ferment, then only the skin is removed before drying | Somewhere between the two above |
| Carbonic maceration | Carbon dioxide is injected into the sealed tank | Often described as winey; borrowed from winemaking |
| ASD (anaerobic slow dry) natural | Anaerobic natural with drying stretched to 60 days or more | Very concentrated fruit |
| Double anaerobic | No standard definition; the name suggests two sealed stages | Read the roaster's process notes |
| Co-ferment | Outside ingredients (fruit, pulp, spice, yeast) ferment with the coffee | Flavors that may come from the added ingredient |
Process descriptions from Coffee Review (2021), Sprudge (2022) and Perfect Daily Grind (2025).
Anaerobic natural vs anaerobic washed
The tank is only half the story. After fermentation, a producer can dry the beans inside the whole fruit (natural) or wash the fruit off first (washed). Drying in the fruit adds more sugar and fruit character, so an anaerobic natural is usually the wilder of the two. An anaerobic washed coffee keeps more of the clean, bright structure that washed coffees are known for.
Double anaerobic
No industry body defines "double anaerobic," and we could not find a reputable source that sets one standard. The name implies two separate sealed fermentation stages, but the length, temperature and order differ from producer to producer. Treat it as a roaster's description, and read their process notes for the details.
Co-ferment and infused coffees
A co-ferment adds something to the tank. Perfect Daily Grind describes co-fermentation as adding outside organic material, such as fruit pulp, wine musts or cacao pulp, during fermentation. Some producers also add chosen yeast strains, which is called yeast inoculation. "Infused" coffees go further and may use flavorings.
These coffees are the most debated part of the category, because the terms have no formal definitions and disclosure varies. In 2024 the Specialty Coffee Association of Panama disqualified co-fermented and infused coffees from its Best of Panama competition, calling them altered. Other people in the industry argue the answer is clear labeling. If a cinnamon or strawberry note matters to you, check whether the roaster says the coffee was co-fermented with that ingredient.
Is anaerobic coffee better than washed or natural coffee?
Anaerobic coffee is different from washed or natural coffee, and whether it is better depends on what you like. It tends to score well with professional cuppers and delivers bold, distinctive flavor. Drinkers who want a classic, clean cup may find it too much, and it usually costs more because the process is riskier.
Here is a simple way to decide. If you enjoy fruity natural Ethiopians, berry-forward light roasts or wine, an anaerobic natural is a fun next step. If you drink a balanced medium roast with milk every morning and love it, an anaerobic coffee may feel loud. Start with an anaerobic washed coffee if you want a gentler introduction.
Price is the other factor. Anaerobic lots are small and take more work, so expect them to sit near the top of a roaster's range. Buying one as a treat alongside your everyday coffee is a sensible way to try the style.
How should you brew anaerobic coffee?
Brew anaerobic coffee the way you would brew any good light roast: fresh-ground, with clean water just off the boil, using a pour-over, AeroPress or quality drip machine. Filter methods show off its fruit and sweetness. Many anaerobic coffees are roasted light, so a slightly finer grind can help pull out the sweetness.
No special recipe is needed. A common starting point is about 1 gram of coffee to 16 grams of water, then adjust to taste. If the cup tastes sour or thin, grind a little finer. If it tastes harsh or drying, grind a little coarser. Lesson 03 on beginner home brewing walks through the basics step by step.
Anaerobic coffees can also work as espresso, especially medium-roast ones built for it. Expect a fruitier, more intense shot than a classic chocolate-and-nut espresso.
Which anaerobic coffees should you try?
Good anaerobic coffees to start with include an anaerobic natural from Colombia or Ethiopia for the full fruit experience, an anaerobic washed coffee for a gentler cup, and a co-ferment if you are curious about the newest styles. These picks from our catalog cover all three, with tasting notes as the roasters list them.
Black & White Coffee Roasters Diego Horta Anaerobic Natural
A lighter-roasted anaerobic natural from Huila, Colombia. The roaster lists black cherry, cherry cordial, marzipan and spiced orange. It suits someone who wants to taste the style at full volume.
Red Rooster Coffee Ethiopia Worka Sakaro Anaerobic
A light-roast anaerobic natural from Gedeb, Ethiopia. The roaster lists blueberry, fig and cocoa. A natural first step for anyone who already likes fruity Ethiopian coffees.
Onyx Coffee Lab Ecuador La Papaya Anaerobic
An anaerobic natural from Ecuador. The roaster lists cherry, honey, stone fruit and a winey note. Good for wine drinkers.
Onyx Coffee Lab Nepal Illam Natural
An anaerobic natural from Nepal, an origin you rarely see in the US. The roaster lists blood orange, kumquat, black tea and cacao nib. It suits explorers who want an unusual origin and process in one bag.
Coffee Bros. Ember Seasonal Espresso
A medium-roast washed anaerobic coffee from Nariño, Colombia, sold as an espresso. The roaster lists plum and cocoa. A gentler entry point, and a good fit for home espresso drinkers.
Black & White Coffee Roasters Esteban Zamora Cinnamon Anaerobic
A lighter roast from Tarrazú, Costa Rica, processed as what the roaster calls a cinnamon anaerobic. The roaster lists cinnamon roll, baked apple and orange zest. Read the roaster's notes for how the cinnamon character was achieved.
Black & White Coffee Roasters Sebastian Ramirez Red Fruits
A medium-roast co-ferment from Quindío, Colombia. The roaster lists cooked strawberry, grape candy and peach. It suits someone who wants to try a co-ferment and judge the style for themselves.
Hula Daddy Kona Coffee Kahiko Cinnamon
A co-fermented coffee from Kona, Hawaii. The roaster lists cinnamon and warm spice. An option for Kona fans who want something outside the classic Kona profile.
Browse more on Explore coffees or see Black & White Coffee Roasters, who list many experimental lots.
Frequently asked questions
What does anaerobic mean on a coffee bag?
It means the coffee fermented in a sealed container with little or no oxygen before it was dried. Carbon dioxide from fermentation pushes the oxygen out, which changes the microbes at work and the flavors they create.
What does anaerobic coffee taste like?
Usually more intense than a washed coffee, with fuller body, more sweetness and ripe or boozy fruit. Many lots have a tangy, lactic edge, and some show spice, wine or even cheese-like notes.
What is the difference between anaerobic natural and natural coffee?
Both dry inside the fruit. A regular natural ferments open to the air while it dries. An anaerobic natural first ferments in a sealed, low-oxygen tank, usually for about one to six days, which tends to make the fruit flavors bigger and stranger.
What is double anaerobic coffee?
There is no standard definition. The name suggests two sealed fermentation stages, but the details vary by producer. Read the roaster's process notes to see what was actually done.
Is co-fermented coffee flavored?
Co-fermented coffee has something extra, such as fruit pulp, spice or chosen yeast, added to the fermentation tank. That addition can shape the flavor. Terms like co-fermented and infused have no formal definitions, so check how the roaster describes the process.
Sources: Coffee Review, Fun With Ferment: Anaerobically Processed Coffees (2021) · Sprudge, What Does Anaerobic Fermentation Mean for Coffee? (2022) · Perfect Daily Grind, Co-ferments vs. Yeast Inoculation: What's the Difference? (2025) · Sprudge, The Specialty Coffee Association of Panama Doesn't Care for Co-Fermentation (2024)