Fourteener Coffee Club
What is anaerobic coffee?
Anaerobic coffee is coffee fermented without oxygen during processing, in sealed bags, tanks or barrels, before it is dried. Shutting out air changes which microbes do the work, and so which flavor compounds end up in the bean. In the sealed-bag method Wikipedia describes, the cup tastes of wild red fruit with a sharp acidity.
Why coffee is fermented at all
Every coffee cherry has a sticky fruit layer, the mucilage, clinging to the bean. In the classic washed process, Wikipedia's coffee production article explains, microbes ferment that layer away over roughly twelve to thirty-six hours before the beans are washed. The article calls fermentation a stage that has to be watched closely, or the coffee turns sour.
Anaerobic processing changes one variable in that step: oxygen. The article describes how much oxygen the fermentation gets as a further variable producers can control, and that is the lever anaerobic lots pull.
How anaerobic fermentation is done
There is no single recipe. The Wikipedia article describes two approaches.
- Sealed bags. In the Indonesian Labu method, pulped fruit is sealed in polypropylene bags with as much air pushed out as possible, so anaerobic organisms take over and produce compounds unlike those from an open tank. Fermentation takes longer, and the bags have to be turned.
- Carbonic maceration. Named for the winemaking technique, it ferments the fruit under carbon dioxide, which stops normal respiration and shifts the mix of microorganisms. In a Thai trial of a semi-carbonic version held at 15 or 20 °C for ten days, the coffee scored higher than a pulped natural comparison for fragrance, flavor, aftertaste, body and balance.
The article points out that the authors of The Craft and Science of Coffee compare this directly with winemaking, where control of fermentation is decisive, and suggest coffee has yet to adopt vessels that control temperature, pH, oxygen and microbes all at once.
What anaerobic coffee tastes like
The Labu method's cup is described in the article as tasting of wild red fruit with a sharp acidity. Because shutting out oxygen changes which compounds form, an anaerobic lot can taste quite unlike the same farm's washed coffee. In the Thai carbonic trial, researchers identified 51 volatile compounds across the different treatments. The roaster's tasting notes on the bag are the best guide to a given lot.
Anaerobic vs open-tank washed vs natural
| Open-tank washed | Natural | Anaerobic | |
|---|---|---|---|
| Oxygen during fermentation | Open to air | Open to air, fruit drying whole | Shut out: sealed bags, tanks or carbon dioxide |
| Fruit during fermentation | Skin removed, mucilage fermented off | Whole cherry | Varies by producer |
| Cup, per Wikipedia | Cleaner, brighter | Fuller, fruitier, sweeter | Wild red fruit, sharp acidity (Labu method) |
The neighbors in more depth: natural process and honey process.
Anaerobic and experimental lots from Colorado roasters
A few roasters we list sell anaerobic or experimental fermentation coffees, checked on their own sites on September 27, 2026. Local favorites, listed; a listing does not mean the roaster is part of the club.
- Wagon in Denver featured an organic Honduras Anaerobic as its coffee of the month.
- Corvus in Denver works with some of its farmers on experimental fermentations and sells experimental fermentation lots beside its core coffees.
- Color in Eagle keeps an Artist Reserve line of experimental lots, including a honey processed co-ferment and a multi-stage washed Chiroso, both from Colombia.
A roaster that stocks experimental lots is betting its own customers will try them. Buying one from a Colorado roaster backs that bet here. Why local roasters matter.
Anaerobic coffee in the club
There is no setting for fermentation style, and we do not promise an anaerobic lot: each Colorado roaster sends from its own lineup. Choose Single origin in the plan builder, and if an experimental coffee arrives and you love it, rate it; your ratings steer the next bag. If it disappoints, the free replacement promise covers it. $16.99 a 12 oz bag, first bag free, you pay $7.99 shipping.
Sources and related terms
Sources:
- Wikipedia, Coffee production (wet process, fermentation, Labu method, carbonic maceration)
- Wikipedia, Geisha (coffee) (washed and natural cups)
- Colorado roaster facts: the roasters' own pages as summarized on our roaster profiles, checked 2026-09-27.
By Joe McRose, Fourteener Coffee Club. Updated .