How Is Decaf Coffee Made? Swiss Water, CO2 and Solvent Methods Explained

Decaf does not grow on trees. Apart from a few rare wild species, every coffee bean contains caffeine, so every cup of decaf starts as a normal green bean that has been treated before roasting. So how is decaf coffee made? In every method, the green beans are first softened with water or steam, then a solvent carries the caffeine out: water with carbon filters (Swiss Water), pressurized carbon dioxide, or an organic solvent such as ethyl acetate or methylene chloride. The beans are then dried and roasted like any other coffee.

The differences between methods matter for taste, cost and labeling. This guide explains each one simply, how decaf began, what the rules say about leftover caffeine and how to choose.

Key takeaways

• Caffeine is removed from green (unroasted) beans, never from roasted coffee.
• The three main families are solvent methods (methylene chloride or ethyl acetate), the Swiss Water Process (water and carbon filters) and supercritical CO2.
• Decaf is not caffeine-free: the FDA says an 8 oz cup typically has 2–15 mg.
• The US standard is a 97% reduction in caffeine; EU rules cap decaffeinated coffee extracts at 0.3% caffeine in the dry matter.
• Good green coffee, gentle processing and fresh roasting matter as much as the method.

In this article

1. A short history of decaf
2. The basic principle
3. Solvent methods
4. The Swiss Water Process
5. The supercritical CO2 method
6. The methods compared
7. How much caffeine is left?
8. Does decaf taste different?
9. FAQ

A short history of decaf

Commercial decaf began in Germany. Ludwig Roselius, a coffee merchant from Bremen, developed the first commercially successful process in the early 1900s and patented it in 1905 or 1906 (sources give both years). The company story says it started with a shipment of beans soaked by seawater that had lost much of its caffeine, a tale worth enjoying but not taking as documented fact.

Roselius steamed the beans with acids or bases and then used benzene as the solvent. His coffee was sold as Kaffee HAG in Germany and much of Europe, as Café Sanka in France and later as Sanka in the United States. Benzene was later abandoned, and today it is not used for coffee.

The 20th century brought gentler methods. The Swiss Water idea was first developed in Switzerland in the 1930s and commercialized around 1980, and in 1967 the German chemist Kurt Zosel, at the Max Planck Institute for Coal Research, found that caffeine dissolves in supercritical carbon dioxide. He filed his decaffeination patent in 1970.

The basic principle

Whatever the method, decaffeination follows the same logic:

1. Open the bean. Green coffee is hard and dry. Steam or hot water makes it swell so caffeine can move.
2. Extract the caffeine. A solvent that attracts caffeine flows through or around the beans.
3. Recover the solvent or clean it. The caffeine is separated out, often to be sold to drinks and pharmaceutical companies.
4. Dry the beans. They return to a stable moisture level and are shipped to roasters.

The hard part is removing caffeine while leaving behind the sugars, acids and aroma precursors that will become flavor in the roaster.

Solvent methods

Solvent methods are the most widely used worldwide. They come in two styles:

• Direct method: the steamed beans are rinsed repeatedly with the solvent, then steamed again to remove it.
• Indirect method: the beans are soaked in hot water, the water (now holding caffeine and flavor) is treated with the solvent to strip the caffeine, and the water goes back to the beans so they reabsorb their flavor. In the US this is often called the European Method.

Methylene chloride

Methylene chloride (dichloromethane) is very selective for caffeine and boils at about 40 °C (104 °F), far below roasting temperatures, which is one reason it has been used for decades. The FDA allows it in decaffeinated coffee with a residue limit of 10 parts per million.

It is also under review. In December 2023, the Environmental Defense Fund and other groups petitioned the FDA to withdraw its approval as a food additive, arguing it is a carcinogen. The National Coffee Association opposes the petition and says decaf made this way is safe within existing limits. The FDA reopened comments in 2026 and, as of October 2026, has not announced a decision.

Ethyl acetate

Ethyl acetate is a compound found naturally in fruit and in fermentation. Some decafs, notably from Colombia, use ethyl acetate made from fermented sugarcane and are sold as “sugarcane decaf.” You may see these labeled “naturally decaffeinated,” but the process is still a solvent method. Fans like its sweet, fruity character.

The Swiss Water Process

The Swiss Water Process uses no added chemical solvent: just water, time and activated carbon. The clever part is how it protects flavor:

1. A first batch of green beans is soaked in hot water. Caffeine and flavor compounds dissolve, and those first beans are discarded.
2. The water passes through activated carbon filters that trap caffeine.
3. What remains is water already saturated with coffee’s soluble flavor compounds but free of caffeine, called green coffee extract.
4. New beans are soaked in this extract. Because the water already holds those flavor compounds, mainly caffeine moves out of the beans.
5. The cycle repeats until about 99.9% of the caffeine is removed, then the beans are dried.

The process is more expensive than solvent methods, partly because the caffeine trapped in the carbon is not resold, and only a few plants in the world use it. The company that runs it today is based in Burnaby, British Columbia, Canada.

The supercritical CO2 method

Carbon dioxide becomes “supercritical” above 31 °C and about 74 bar. In that state it flows like a gas but dissolves things like a liquid, and it is quite selective for caffeine.

In Zosel’s patented process, moistened beans sit in a pressure vessel while CO2 at about 70 °C and 162 bar flows through them, carrying caffeine out. The CO2 is then cleaned, for example through activated carbon, and reused. The Max Planck Society says this method now processes around 100,000 tonnes of raw coffee a year worldwide. It is mostly used for large commercial volumes because the equipment is costly.

The methods compared

How much caffeine is left?

Decaf means “mostly decaffeinated”, not zero.

For comparison, the FDA lists 113–247 mg for a 12 oz cup of regular brewed coffee. If you are cutting back, decaf removes most of your caffeine, but several large mugs still add up. Our article on coffee addiction explains why some people feel withdrawal when they switch suddenly and how to taper.

Does decaf taste different?

Every method removes a little more than caffeine, and the soaking and drying change the beans physically, so roasters usually adjust their roast for decaf. Caffeine itself also contributes some bitterness, so a decaf cup can taste a little softer.

In practice, three things decide whether a decaf tastes good:

• The green coffee. Decaf made from good specialty beans tastes far better than decaf made from leftovers.
• The process. Water and CO2 methods are often chosen to protect origin character; sugarcane decaf adds sweetness.
• Freshness. Decaf goes stale like any coffee. Old decaf is where its reputation comes from.

Our decaf and lower-caffeine coffees

Our Peru Decaf is a fully washed single origin from the Norandino cooperative in Piura and Amazonas, decaffeinated with the Swiss Water Process, with notes of caramel, citrus and a smooth body. For espresso lovers, Decaf Espresso is a water-process decaf roasted dark for a rich, chocolatey shot. If you want to cut back rather than cut out, Half Caf blends regular coffee with water-process decaf for half the caffeine. All are roasted 1–5 days before delivery.

Decaf coffee FAQ

Is decaf coffee made with chemicals?

Some decaf uses solvents (methylene chloride or ethyl acetate) and some does not (Swiss Water uses water and carbon; the CO2 method uses carbon dioxide). The label or the roaster can tell you which method was used.

How much caffeine is in decaf coffee?

The FDA says an 8 oz cup of decaf typically contains 2–15 mg of caffeine, compared with well over 100 mg in a regular 12 oz cup.

Is Swiss Water decaf 100% caffeine-free?

No. It removes about 99.9% of the caffeine, so a tiny amount remains.

When is the caffeine removed?

Before roasting, while the beans are still green. Roasted beans are too fragile and would lose their flavor.

Who invented decaf coffee?

The first commercially successful process is credited to Ludwig Roselius of Bremen, Germany, patented in 1905–06 and sold as Kaffee HAG.

Sources

1. Max Planck Society, “Coffee withdrawal” (Kurt Zosel and CO2 decaffeination), 2014. Link
2. Wikipedia, “Decaffeination”, accessed 2026. Link
3. US Food and Drug Administration, “Spilling the Beans: How Much Caffeine Is Too Much?” Link
4. US Code of Federal Regulations, 21 CFR 173.255, Methylene chloride. Link
5. Daily Coffee News, “FDA weighs next steps on decaf solvent rules following new comments”, June 30, 2026. Link
6. Council Directive 1999/4/EC relating to coffee extracts and chicory extracts. Link
7. JURA, “Decaffeination: the Swiss Water Process”. Link

Facts checked in October 2026.

This article is for general information only and is not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor before changing your caffeine intake.

Keep reading: Coffee addiction · Benefits of caffeine · Shop single origins