# How Is Decaf Coffee Made?

> Four industrial processes — Swiss Water, CO2, ethyl acetate and methylene chloride — explained, with what each does to flavour and safety.

Topic: Caffeine & Decaf  
Published: 2026-08-30T09:55:00-04:00  
Updated: 2026-08-30T09:55:00-04:00  
Author: Mical Robert, Editor (https://trysix.online/author/mical-robert)  
Canonical: https://trysix.online/how-is-decaf-coffee-made

## The short answer

Caffeine is washed out of green beans before roasting, then captured. Four methods do it: Swiss Water, supercritical CO2, ethyl acetate (the sugarcane process) and methylene chloride. All must remove at least 97 percent to be sold as decaf.

## Key takeaways

- Decaffeination always happens to green beans, before roasting — never to the finished coffee.
- Every method works the same way: dissolve the caffeine out, then get it out of the solvent.
- Swiss Water and CO2 use no chemical solvents. Ethyl acetate occurs naturally in fruit.
- Methylene chloride residues are capped at 10 parts per million and typically measure far below that.

Decaf has a reputation problem, and a lot of it comes down to a vague sense that chemicals are involved. Some of that worry is fair and some of it is not, and the difference is worth understanding — mostly because it tells you which bag on the shelf is worth buying.

## The shared principle

Every decaffeination method does the same three things. Steam or soak the green beans so they swell and the caffeine becomes mobile. Wash the caffeine out with something it dissolves into. Then dry the beans and return them for roasting.

The difficulty is that caffeine is not the only thing that dissolves. Sugars, acids and flavour precursors come out alongside it, which is why decaf historically tasted flat. The differences between the four methods are mostly about how well they put those compounds back or leave them alone.

> **Always before roasting** — You cannot decaffeinate roasted coffee, and nobody does. This is why the roast date on a decaf bag matters: the beans have already been through an extra processing step and an extra leg of the supply chain before they reach the roaster.

## The four processes

**How each commercial method works, and what it is known for.**

| Process | What removes the caffeine | Solvent-free | Reputation |
| --- | --- | --- | --- |
| Swiss Water | Water plus carbon filters | Yes | Best flavour retention; costlier |
| Supercritical CO₂ | Pressurised carbon dioxide | Yes | Very selective; used at scale |
| Ethyl acetate (sugarcane) | Ethyl acetate from fermented cane | Naturally derived | Slight fruity note; common in Colombia |
| Methylene chloride | Methylene chloride | No | Cheapest; the one that worries people |

## Swiss Water

The most-marketed process, and the one most often named on speciality bags. Green beans are soaked in hot water, which pulls out both caffeine and flavour compounds. That water is passed through activated carbon filters sized to trap caffeine molecules while letting the flavour compounds through.

What is left is a caffeine-free but flavour-saturated water, called green coffee extract. A fresh batch of beans is soaked in it: because the water is already saturated with everything except caffeine, only caffeine diffuses out of the beans. The flavour compounds have nowhere to go.

- No chemical solvent at any stage — water and carbon only.
- Typically achieves 99.9 percent caffeine removal, above the 97 percent requirement.
- More expensive, which is why it appears mostly on speciality coffee.
- The name is a trademark; the underlying idea is a water process, and other companies run comparable ones.

## Supercritical carbon dioxide

Carbon dioxide held above about 74 bar and 31°C becomes supercritical — neither properly liquid nor gas, with the density of a liquid and the diffusivity of a gas. In that state it is a highly selective solvent for caffeine and largely ignores the larger flavour molecules.

Steamed beans are held in a pressure vessel and the supercritical CO₂ is circulated through them. The caffeine-laden CO₂ is then depressurised, at which point the CO₂ returns to gas and the caffeine drops out — and that recovered caffeine goes into soft drinks and pharmaceuticals.

It is the method of choice for large-volume commercial decaf where flavour matters, because the equipment cost is high but the running cost per tonne is low.

**Figure: The four processes at a glance**

| Item | Value |
| --- | --- |
| Swiss Water (Percent removed) | 99.9% |
| Supercritical CO₂ (Percent removed) | 98% |
| Ethyl acetate (Percent removed) | 97% |
| Methylene chloride (Percent removed) | 97% |

_Approximate caffeine removal achieved. All exceed the 97 percent US requirement._

## Ethyl acetate — the 'sugarcane' process

Ethyl acetate is an ester that occurs naturally in ripening fruit and in fermented sugarcane, which is where the process gets its marketing name. Steamed beans are washed repeatedly with it; the caffeine dissolves into the solvent and is carried away, and the beans are then steamed again to drive off residual ethyl acetate.

It is common in Colombia, where sugarcane is abundant, and it often leaves a faint sweetness or fruitiness that some people like and others notice as an off-note. Because the solvent is naturally derived, it is frequently labelled 'natural decaf' — a description that is accurate but does more work in marketing than in chemistry.

## Methylene chloride

The cheapest and historically most widespread method. Methylene chloride, also called dichloromethane, is applied either directly to the beans or indirectly to the water that has soaked them. It is very effective and highly selective for caffeine.

It also has a poor public reputation, and it is worth being precise about where the concern sits. US regulations cap residual methylene chloride in roasted decaf at 10 parts per million. Measured residues in finished coffee are typically far below that, partly because the compound boils at around 40°C and roasting takes the beans past 400°F — several hundred degrees above its boiling point.

> **An honest reading** — The occupational and environmental concerns about methylene chloride are real and are why regulators scrutinise it. Whether the trace residues permitted in coffee present a meaningful consumer risk is a much weaker claim, and the roasting temperatures involved make measurable residue in the cup unlikely. If you would rather avoid it entirely, buy coffee that names Swiss Water, CO₂ or ethyl acetate — bags that name no process are the ones most likely to be solvent-decaffeinated.

## What this means for buying decaf

### Choosing a decaf worth drinking

1. **Look for a named process** — Swiss Water, CO₂ or sugarcane/ethyl acetate. A roaster who names the process generally chose it, which is itself a signal about the rest of the coffee.
2. **Check the roast date** — Decaf has been through more handling and more shipping than regular coffee before roasting. It stales the same way afterwards — see [how to store coffee beans](https://trysix.online/how-to-store-coffee-beans).
3. **Prefer medium roasts** — Decaffeinated beans are structurally more fragile and roast faster, so they scorch easily. Dark decaf is frequently over-roasted, which is where a lot of decaf's bad reputation comes from.
4. **Adjust your grind** — Decaf beans are more brittle and grind finer at the same setting, which can push a brew into over-extraction. Going one step coarser is often the fix — see [how to grind coffee beans](https://trysix.online/how-to-grind-coffee-beans).

Whatever the process, the result still contains a small amount of caffeine by design — around 2 mg in an 8 oz cup. [Does decaf coffee have caffeine](https://trysix.online/does-decaf-coffee-have-caffeine) covers what the residue means in practice.

## Frequently asked questions

### What chemicals are used to decaffeinate coffee?

Four methods are used commercially: Swiss Water uses only water and activated carbon; supercritical CO₂ uses pressurised carbon dioxide; the sugarcane process uses ethyl acetate, an ester found naturally in fruit; and the cheapest method uses methylene chloride.

### Is decaf coffee bad for you because of the chemicals?

The evidence for consumer harm from trace solvent residues is weak. US rules cap methylene chloride in roasted decaf at 10 parts per million, measured residues are typically far below that, and the compound boils at around 40°C while roasting reaches over 400°F. If you prefer to avoid it, buy coffee that names Swiss Water, CO₂ or ethyl acetate.

### Which decaf process tastes best?

Swiss Water and supercritical CO₂ generally retain the most flavour, because both are highly selective for caffeine. The bigger determinant of a good decaf is usually the underlying coffee and how carefully it was roasted — decaf beans scorch easily and are often over-roasted.

### Is coffee decaffeinated before or after roasting?

Always before. Caffeine is removed from green beans, which are then dried and shipped to a roaster. That extra processing and shipping leg is why the roast date on a decaf bag is worth checking carefully.

## Sources

- [The Swiss Water Process](https://www.swisswater.com/) — Swiss Water Decaffeinated Coffee Inc.. Supports the description of the water-and-carbon-filter decaffeination process.
- [21 CFR Part 163 — Cacao Products](https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-163) — U.S. Electronic Code of Federal Regulations. Supports the US regulatory framework for coffee products and decaffeinated labelling requirements.
- [21 CFR 163.5 — Cacao nibs (coffee and cocoa product standards)](https://www.ecfr.gov/current/title-21/section-163.5) — U.S. Electronic Code of Federal Regulations. Supports the regulatory standards applied to coffee and cocoa product composition.

## Related articles

- https://trysix.online/does-decaf-coffee-have-caffeine
- https://trysix.online/decaf-espresso-and-lattes
- https://trysix.online/is-decaf-coffee-a-diuretic
- https://trysix.online/how-to-store-coffee-beans

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