How Is Coffee Decaffeinated? The Four Main Methods Explained

Decaf is made from green beans before roasting, using water and carbon, carbon dioxide, ethyl acetate or methylene chloride. Here's how each works, what the FDA allows and what's left in the cup.

By Jay Arr Updated

This article accompanies our video from December 2019.

Every decaf starts as green coffee. The caffeine comes out before the beans are roasted, and the four methods differ mainly in what carries it away. Here’s how each one works, in the words of the companies that run them, and what the US rules say.

Our 2019 video predates this revision; where its figures differ, follow the text.

What every method has in common

Caffeine dissolves in water, but so does most of what gives coffee its flavor. As Jessica Easto puts it in Craft Coffee: A Manual, water alone would take the caffeine and leave you with tasteless beans. So every method starts by steaming or soaking the green beans so they swell and open up, and then uses something to separate the caffeine from everything else.

Water and carbon: Swiss Water and Mountain Water

Swiss Water, in Delta, British Columbia, says its process “uses only water, temperature, and time.” Its four steps, as the company describes them:

  1. Preparation. The green beans are cleaned and hydrated.
  2. Caffeine migration. The beans meet Swiss Water’s Green Coffee Extract (GCE), a solution of water and coffee’s own soluble compounds that is already free of caffeine. Swiss Water says diffusion then lets only the caffeine move out of the beans. Easto explains why: the beans and the extract are already in balance for everything else.
  3. Drying. The beans are dried back down.
  4. Filtration and renewal. The caffeine-laden extract runs through carbon filters that trap the caffeine, and the refreshed extract goes on to the next batch of beans.

Swiss Water says the green coffee leaving its process is 99.9% caffeine free, and that its method keeps a coffee’s certifications, including organic, intact.

Mountain Water is the name Descamex, in Córdoba, Veracruz, Mexico, uses for its water process. Descamex says it steams the beans, then extracts the caffeine under controlled flow, temperature, pressure and vacuum with a saturated, water-based solution of soluble solids from coffee beans, before drying the beans in three stages and polishing them. It says the process removes more than 97% of the caffeine, was patented in 1987 and was certified organic in 2003.

Other decaffeinators run water processes too. Coffein Compagnie in Bremen, Germany, describes its Hanseatic Water Process this way: water extracts the water-soluble substances, caffeine included, from the beans; activated carbon takes the caffeine out of that liquid; and the liquid goes back onto the beans before a final drying.

Carbon dioxide

The CO₂ method comes from the chemist Kurt Zosel at the Max Planck Institute for Coal Research in Germany. The Max Planck Society tells the story: Zosel noticed in 1967 that caffeine dissolves in supercritical carbon dioxide, and he filed a patent three years later. In his process, the beans are moistened with steam and hot water so they swell, then carbon dioxide at 162 bar and 158°F (70°C) passes through water and then through the beans, drawing out the caffeine. The CO₂ is then cooled until it liquefies and passed through activated carbon, which captures the caffeine. In 2014, the Max Planck Society put the method’s use at 100,000 tons of raw coffee a year worldwide.

Not every CO₂ plant works the same way. CR3-Kaffeeveredelung, a decaffeinator in Bremen, describes its vessels as decaffeinating with liquid carbon dioxide.

Easto notes the catch: the equipment is expensive, so the CO₂ method is used mostly by large commercial operations.

Ethyl acetate, sold as “sugarcane” or “EA” decaf

Coffein Compagnie calls its ethyl acetate method the Hanseatic Sugarance Process. Steam removes the beans’ silver skin, the beans take on water to open their structure, and a water and ethyl acetate solution draws out the caffeine over several rounds. Steam then strips out the remaining ethyl acetate, and the beans are dried back to their starting moisture. The company notes that ethyl acetate occurs naturally in sugarcane, coffee and fruits, and is also produced synthetically.

Descafecol, in Manizales, Colombia, says it uses ethyl acetate of natural origin, obtained through a process based on sugarcane, in a water and ethyl acetate process, and that its decaf is 99.9% caffeine free. Swiss Water, a competitor, points out that “EA decaf” and “sugarcane decaf” on a label both mean ethyl acetate, which can be derived from natural sources but often isn’t.

The FDA allows ethyl acetate as a solvent in decaffeinating coffee and tea, under good manufacturing practice (21 CFR 173.228).

Methylene chloride

Methylene chloride, also called dichloromethane (DCM), is the solvent in the FDA petition below. Coffein Compagnie’s DCM method follows the same steps as its ethyl acetate one: steam, a water and DCM solution that extracts the caffeine over several rounds, then steam to remove the remaining DCM and drying. The company says DCM extracts caffeine selectively at relatively low temperatures. Methylene chloride boils at 104°F (40°C), according to the CDC’s NIOSH Pocket Guide.

What the FDA allows. Under 21 CFR 173.255(c), methylene chloride may remain in coffee from its use in extracting caffeine from green beans at no more than 10 parts per million (0.001%) in decaffeinated roasted coffee and in decaffeinated instant coffee. Descamex, which also runs a methylene chloride process, says it takes residues to limits ten times lower than the FDA allows.

What’s under review. A petition from the Environmental Defense Fund and other groups, which the FDA filed in December 2023, asks it to remove methylene chloride and three other solvents from its food additive rules, including the methylene chloride section that covers decaf. The FDA announced the petition in the Federal Register on January 11, 2024, and on May 28, 2026 reopened the comment period, asking for data from the past two years and for what manufacturers would need to phase out the uses if it granted the petition in part or in whole. Comments closed on June 29, 2026. As of October 15, 2026, the FDA’s petition list still shows it as under review, with no decision announced.

Solvents in decaf are not new. The Bremen coffee merchant Ludwig Roselius patented a decaffeination process in 1905 that used benzene, and founded Kaffee HAG the following year. The Max Planck Society notes that by 1970 less poisonous solvents, such as dichloromethane and ethyl acetate, had long since replaced benzene.

How much caffeine is left

Decaf isn’t caffeine free. The FDA says “decaf coffee typically has 2 to 15 milligrams in an 8-fluid-ounce cup,” and adds that if you react strongly to caffeine, “you may want to avoid these beverages altogether.”

Our Caffeine Calculator uses the FDA’s range, so it shows an 8 fl oz decaf at 2–15 mg. Easto’s figure is narrower, 3 to 6 mg per 6 fl oz, about 4 to 8 mg per 8 fl oz (calculated), and sits inside the FDA’s. Either way, several cups add up.

The percentages on decaffeinators’ pages measure something else: how much of the green coffee’s caffeine is gone, or how little is left in the green beans. You’ll often read that US rules require 97% of the caffeine to be removed. We couldn’t find that figure on the FDA’s own pages, so we don’t repeat it as a rule.

If you’re limiting caffeine for a health reason, ask your clinician whether decaf fits, and how many cups.

Choosing and storing decaf

Read the bag. Look for the method by name: Swiss Water, Mountain Water, CO₂, or EA and sugarcane for ethyl acetate. If a bag doesn’t say how the coffee was decaffeinated, ask the roaster.

Treat it like any fresh coffee. In The Physics of Filter Coffee, Jonathan Gagné notes that oils migrate to the surface of the beans faster in decaf, as they do in darker roasts, and oxidize once they get there. The Freshness tool uses the same windows for decaf as for other coffee; going by Gagné’s point, a decaf may fade a little sooner than they suggest. Buy decaf with a roast date, keep it sealed, and freeze what you won’t use within about two weeks. Our freshness timeline and freezing guide cover the details.

Brew it the same way. Start with your usual recipe and grind size, and adjust by taste.

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