What Is Anaerobic Fermentation Coffee?
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Anaerobic coffee is coffee that has been fermented in a sealed, oxygen-free (or very low-oxygen) container during processing, instead of in open tanks or on drying beds. Cutting off oxygen changes which microbes do the work, and that produces bold, unusual flavors such as tropical fruit, cinnamon, red wine or bubblegum. It is one of the most talked-about trends in specialty coffee.
If you have seen “anaerobic natural” or “carbonic maceration” on a bag and wondered what it means, this guide explains the process, where it came from and what to expect in the cup.
What Does Anaerobic Mean in Coffee?
“Anaerobic” simply means “without oxygen.” All coffee goes through some fermentation after harvest: yeasts and bacteria feed on the sugars in the fruit around the seed. In a traditional washed or natural process, that fermentation happens in open air, where oxygen is available.
In anaerobic processing, the producer places coffee, either whole cherries or depulped beans, inside a sealed tank, barrel or bag. As fermentation begins, the microbes use up the remaining oxygen and release carbon dioxide. Many tanks are fitted with a one-way valve so gas can escape without letting air back in. The result is a controlled environment where the producer can manage time, temperature and pressure much more precisely than in an open fermentation.
If you are new to processing in general, start with the basics of washed, natural and honey coffee, then come back here. Anaerobic methods are best understood as a variation layered on top of those classic methods.
How Anaerobic Coffee Is Made
Methods vary from farm to farm, and many producers guard their exact recipes. A typical anaerobic process looks like this:
- Harvest and sort. Only ripe, sound cherries are used, because any defect will be amplified by a long fermentation.
- Load the tank. Whole cherries (for an anaerobic natural) or depulped beans in their mucilage (for an anaerobic washed or honey) go into a sealed container.
- Ferment without oxygen. The container stays closed for anywhere from about a day to several days. Producers monitor temperature, pH and sometimes sugar levels to decide when to stop.
- Finish the process. After fermentation, the coffee is dried as a natural, washed or honey would be, often slowly on raised beds.
- Rest and mill. Once dry, the beans rest before hulling, sorting and export.
Carbonic Maceration: Anaerobic Coffee's Famous Cousin
Carbonic maceration is a specific type of anaerobic fermentation borrowed from winemaking. In France's Beaujolais region, winemakers ferment whole Gamay grapes in tanks filled with carbon dioxide, which gives those wines their bright, fruity character.
In coffee, carbonic maceration means sealing whole cherries in a tank and filling it with carbon dioxide, rather than simply letting the fermentation consume the oxygen. The fruit begins fermenting from the inside, and the coffee absorbs intense fruity and wine-like aromas.
The technique gained worldwide attention in 2015, when Australian barista Saša Šestić won the World Barista Championship using a carbonic macerated Sudan Rume coffee from Colombia. After that win, more producers began experimenting with sealed-tank fermentation, and anaerobic lots became a regular sight on specialty menus and at competitions.
Anaerobic vs Carbonic Maceration
All carbonic maceration is anaerobic, but not all anaerobic coffee is carbonic maceration. A plain anaerobic process lets fermentation naturally push out the oxygen. Carbonic maceration adds carbon dioxide deliberately and uses whole cherries.
What Does Anaerobic Coffee Taste Like?
Anaerobic coffee is known for intensity. Common tasting notes include:
- Tropical and candied fruit: pineapple, mango, passion fruit, strawberry candy.
- Wine and liqueur notes: red wine, rum, cherry liqueur.
- Spice: cinnamon, clove and baking spice, which surprise many first-time drinkers.
- Heavy sweetness and a syrupy body.
Some people love this style; others find it too far from what coffee “should” taste like. It is a bit like comparing a natural wine to a classic one. A well-made anaerobic lot is vivid and clean, while an over-fermented one can taste boozy, vinegary or funky.
Anaerobic vs Traditional Processing: A Quick Comparison
| Process | Oxygen during fermentation | Typical flavor | Consistency |
|---|---|---|---|
| Washed | Open tanks, oxygen present | Clean, bright, origin-driven | High |
| Natural | Open air on beds or patios | Fruity, heavy, sweet | Medium |
| Anaerobic | Sealed, oxygen depleted | Intense fruit, spice, wine | Depends on producer skill |
| Carbonic maceration | Sealed, filled with carbon dioxide | Very fruity, winey, aromatic | Depends on producer skill |
Is Anaerobic Coffee Worth Trying?
If you enjoy exploring flavor, yes, at least once. Here is who tends to love it, and who may prefer something else:
- Try it if you like fruity naturals, enjoy wine or craft beer, or want a conversation-starter cup for guests.
- Skip it if you want a classic, chocolatey, everyday coffee for your morning routine or a strong cup before training.
- Expect to pay more. Anaerobic lots take extra equipment, monitoring and risk, so they usually cost more than traditional coffees.
Brewing Tips
Anaerobic coffees often shine as pour-over, where their aromatics come through clearly. Start with a standard ratio, such as the ones in our coffee to water ratio guide, and adjust from there. As espresso, they can be very intense, so a slightly longer shot may balance them. Freshness matters too: fermented aromatics fade as coffee ages, and very fresh beans need a few days to release gas, as explained in our article on coffee degassing.
Anaerobic Coffee FAQ
Does anaerobic coffee contain alcohol?
No meaningful amount. Fermentation happens to the fruit and beans before drying and roasting, and roasting drives off volatile compounds. Your brewed cup does not contain alcohol.
Is anaerobic coffee stronger?
It tastes more intense, but processing is not a meaningful factor in caffeine content. Caffeine depends mainly on the species and on how much coffee you brew.
Why does anaerobic coffee taste like cinnamon?
The low-oxygen environment encourages different microbes and fermentation byproducts than open-air processing. Some of those compounds read as warm spice, which is why cinnamon notes are common, even though no spice is added.
Is anaerobic coffee the same as flavored coffee?
No. Anaerobic flavors come from fermentation, not from added flavorings. Flavored coffee, by contrast, is roasted coffee finished with flavor after roasting.
Explore Fruit-Forward Coffee at Feel Espresso
Feel Espresso does not currently sell anaerobic lots, but if anaerobic coffee has you curious about fruit-driven flavors, a great natural process coffee is the perfect next step. Try our jammy, aromatic Ethiopia Natural, the bright, juicy Kenya, or explore all our single origin coffees. Every order is roasted 1–5 days before delivery, so those delicate fruit notes arrive at their best.