How Is Coffee Decaffeinated? The Four Methods, Explained

All decaffeinated coffee starts the same way: green, unroasted beans are soaked or steamed so that their caffeine can move, and then something draws the caffeine out. What differs between the methods is that something — a chemical solvent, water and carbon filters, or carbon dioxide under pressure. After that the beans are dried and roasted like any other coffee.

Each method has trade-offs in cost, flavour and how people feel about it, and one of them is currently the subject of a regulatory fight in the United States.

Why it happens before roasting

Caffeine is spread throughout the green bean, bound up in its cellular structure. Green coffee is tough, dense and stable, and it can be soaked, steamed and dried without falling apart. Roasted coffee is brittle and full of fragile aromatic compounds that would be stripped away by any process aggressive enough to remove caffeine. So decaffeination is always done to green coffee, and the roasting comes afterwards.

The four methods

Methylene chloride

The beans are steamed to open them up, then rinsed repeatedly with methylene chloride (dichloromethane), a solvent that binds to caffeine. In some versions the solvent touches the beans directly; in others, the caffeine is first soaked out into water and the solvent is used to strip it from that water before the water goes back to the beans. Either way, the beans are then steamed again to drive off the solvent.

Methylene chloride boils at around 40 °C, so very little survives steaming, and coffee roasting reaches temperatures far above that. This method is cheap, efficient and good at leaving flavour compounds behind, which is why it remains common. It is often called the "European method".

Ethyl acetate

The process is similar, but the solvent is ethyl acetate, a compound that occurs naturally in fruit. That is why coffee decaffeinated this way is sometimes labelled "naturally decaffeinated", even when the ethyl acetate was made industrially. Some decaf sold as "sugarcane process" uses ethyl acetate made by fermenting sugarcane. Ethyl acetate can leave a faint fruity note, which many people do not mind.

The Swiss Water Process

This is the solvent-free method, and its trick is elegant.

Green beans are soaked in hot water, which pulls out caffeine and everything else soluble. That first batch of beans is discarded, but the water — now saturated with every soluble compound in coffee except, once filtered, caffeine — becomes the working solution, called green coffee extract. Activated carbon filters remove the caffeine from it.

Fresh beans are then soaked in this extract. Because the water is already saturated with coffee's flavour compounds, those compounds have no reason to leave the beans. Caffeine is the only thing the water lacks, so caffeine is the only thing that moves. The extract is filtered through carbon again and reused.

The method was developed in Switzerland in 1933 and commercialised in 1980. It is usually more expensive than solvent methods.

Supercritical carbon dioxide

Carbon dioxide, pressurised and heated past its critical point, behaves partly like a gas and partly like a liquid, and it is very good at dissolving caffeine selectively. Moistened green beans are exposed to it in a pressure vessel; the CO₂ carries caffeine away and is then separated from it and reused.

The method was developed by Kurt Zosel at the Max Planck Institute in Germany. It needs expensive equipment, so it is used at large scale, and it is well regarded for preserving flavour.

How much caffeine is left

Decaf is not caffeine-free; it has most of its caffeine removed.

In practice that leaves a few milligrams per cup, against roughly 95 mg in a regular cup of filter coffee — the caffeine guide has the figures by drink. For almost everyone that is negligible, though a very caffeine-sensitive sleeper might still notice an evening cup or two. The coffee and sleep guide covers how small doses affect sleep.

The methylene chloride debate

Methylene chloride is a probable carcinogen at high exposures, and the US Environmental Protection Agency has restricted it heavily in industrial and consumer uses. Its use in food is regulated separately, by the Food and Drug Administration, which allows residues of up to 10 parts per million in decaffeinated roasted coffee and decaffeinated soluble coffee.

In December 2023 a coalition including the Environmental Defense Fund and Breast Cancer Prevention Partners petitioned the FDA to remove the food-additive authorisations for four solvents, methylene chloride among them, arguing that a substance found to cause cancer in humans or animals cannot legally remain authorised as a food additive. The National Coffee Association opposes a ban, arguing that decaf made this way is safe within the existing limits and that around 26 million Americans drink decaf daily.

The FDA reopened public comment on the petition in 2026, and the extended comment period closed on 29 June 2026. As of the latest reports in mid-2026, the agency had not announced a decision, and until it does, the 10 ppm limit remains the US rule.

There is no need to wait for that decision to make your own choice. If you would rather avoid solvent decaf, the label will usually say: look for Swiss Water Process, CO₂ or sugarcane / ethyl acetate decaf. If a bag of decaf names no method, it is often the solvent kind.

Why decaf tastes different

Decaf has a reputation for tasting flat, and some of that is earned.

• Decaffeination removes more than caffeine. Every method loses some flavour compounds, though the best lose very little.
• Caffeine is a little bitter. Research by Thomas Hofmann's group found caffeine accounts for only about 15% of coffee's bitterness, so removing it changes the cup slightly but not dramatically — the bitter and sour guide explains where the rest comes from.
• Decaf is harder to roast. Decaffeinated green beans start out darker and behave differently in the roaster, so the colour cues roasters rely on are less useful, and decaf is easy to over-roast.
• Decaf has often been made from cheaper coffee. For decades it was an afterthought. That has changed: plenty of specialty roasters now decaffeinate excellent single-origin coffees, and the results can be hard to tell from the original.

A short history

The first commercially successful process came from Ludwig Roselius, a coffee merchant in Bremen, in 1903. According to the story he told, it began with a consignment of beans soaked in seawater during shipping, which had lost much of its caffeine but little of its flavour. His process used benzene as the solvent, and his coffee was sold as Kaffee HAG in Europe and as Sanka in the United States.

Benzene is now known to be a carcinogen, and it has long since been replaced. Modern decaf — whether by solvent, water or CO₂ — is a very different product from the one Roselius sold, and the best of it is simply coffee that happens not to keep you up.