Air roasting is a coffee roasting method that uses a stream of hot air to heat the beans instead of a hot metal drum. The air lifts the beans and keeps them moving, so no bean sits against a hot surface. Roasters also call it fluid bed roasting, because the floating beans behave like a liquid. Engineer Michael Sivetz built the first commercial version in the 1970s, and the design still runs in roasteries today.
This guide explains what air roasting is, how the machines work step by step, what the method changes in the cup, and what it asks of your space and utilities.
Air roasting roasts green coffee in a stream of hot air. A blower pushes heated air up through a chamber. The beans lift off the bottom and tumble in that stream for the whole roast. Heat reaches the bean through the moving air, which is convection, and almost none of it comes from touching a hot surface.
Drum roasting works the other way. The beans sit inside a turning metal drum and pick up heat from the drum wall as well as from the air around them.
You will see three names for the same method: air roasting, hot air roasting and fluid bed roasting. "Fluid bed" describes what the beans do. Once enough air moves through them, the whole batch flows and churns like a boiling liquid. On a bag of coffee, "air roasted" simply tells you the roaster used this type of machine.
Air roasting is not a new idea. Michael Sivetz, a chemical engineer, developed the original fluid bed design in the 1970s, and his machines are still in service. For how roasting works whatever the machine, start with our coffee roasting basics.
A fluid bed roaster, also called an air roaster. It is the one roaster type where hot air does nearly all the work.
Every roaster uses some hot air. A drum roaster pulls air through the drum while the drum wall also heats the beans, so it splits the job between contact and airflow. A fluid bed roaster removes the drum. There is no hot wall for the beans to touch, so the air carries the heat, moves the beans and clears the chaff all at once.
If a question asks which machine relies mostly on hot air, the answer is the fluid bed or air roaster.
Five things happen inside the chamber, from cold green coffee to cooled roasted beans.
A burner or an electric element heats the air. A blower drives that air up into the roasting chamber. The air is the roasting medium here, so the machine controls the roast by changing air temperature and air speed.
Green coffee drops into the chamber and the rising air lifts it off the bottom. The batch starts to churn and flow. This is the fluid bed. Every bean keeps moving, so no bean parks against a hot spot.
The air touches every side of every bean, over and over. That constant contact spreads heat through the batch evenly. Roasters often describe the result as a clean roast with little variation between beans.
Beans shed their silver skin as they roast. That papery waste is chaff. In a drum, chaff can sit in the hot chamber and scorch, which pushes smoky and bitter notes into the batch. In an air roaster the same airflow that lifts the beans carries the chaff straight out to a separate collector.
When the beans hit the target roast level, the machine switches the hot air for cool air. The beans stop roasting quickly. Fast cooling matters, because beans left hot keep developing past the point you aimed for.
Two parts of the process shape the flavor.
First, nothing scorches. No bean rests on a hot wall, so you avoid the tipping and facing marks that come from surface contact. Roasters who move to air often say the cup tastes cleaner and brighter, with the origin character easier to pick out.
Second, the chaff leaves during the roast. Burning chaff adds smoke and a dry, bitter edge. Pulling it out as it sheds keeps that out of the batch.
There is a trade here, and roasters disagree about it. Convection-only heat builds clarity well. Many roasters find it builds body less than a drum does. Neither result is better on paper. It depends on what you want in the cup and what your customers buy.
Most air roasters read bean temperature with a thermocouple and log it, so you can save a profile and repeat it. That repeatability is why cafes that roast their own coffee like the format.
If you are weighing the two methods against each other, the full side-by-side covers heat transfer, roast times, batch sizes, fuel and chaff handling point by point: read drum roaster vs air roaster.
Less space than a drum roaster of the same batch size, but not nothing. The small machines are simple to place. Past sample size, an air roaster needs the same three things any roaster needs: a power or fuel supply, a way to move air out, and somewhere for the chaff to go.
The machine above is a 35 kg Sivetz roaster built in 2006, still in use and running on natural gas.
Power or fuel. Do not assume an air roaster is a plug-in appliance. Across the air roasters that have come through CoffeeTec with a fuel type recorded, slightly more than half ran on natural gas or propane rather than electricity. Check the data plate before you budget for the install.
Venting. The airflow that clears chaff has to go somewhere. Larger air roasters need ducting, and local air-quality rules may call for emissions control. Our guide on afterburners and air-quality permits covers what regulators look for.
Chaff handling. Chaff collects fast and it is dry and light. Build emptying the collector into the daily routine.
Two patterns show up in the air roasters that reach us, and the numbers below come from our own intake records rather than from manufacturer claims.
The first is how few builders there are. Three names cover nearly every air roaster that reaches us: Coffee Crafters (Artisan, X-e and Valenta), Sivetz and Sonofresco. If someone tells you they run an air roaster, it is very likely one of those three.
The second is how long these machines last. Air roasters arriving at CoffeeTec carry build years from 1990 through 2024, and the units from the 1990s still come in running. There is not much inside a fluid bed roaster to wear out: a blower, a heat source and a chamber. Keep the airflow path clean and the machine keeps going. [CoffeeTec team: add the one thing that most often needs attention on an older fluid bed machine when it arrives, for example a blower bearing, a worn screen or a burner that needs re-rating.]
You can see what is on the floor now in the air roasters collection, which runs from 1 lb Sonofresco sample machines up to production Sivetz systems. Two that show the range: the 2 lb Sonofresco profile roaster for a cafe roasting its own, and the Coffee Crafters Valenta 8 for a small roastery. For model-by-model detail, read our fluid bed roaster buying guide.
Roasters switch formats as their volume and their coffee change. A cafe that starts on a 1 lb Sonofresco often wants more capacity within two years. A production roastery adding a clean, bright single-origin line sometimes adds an air roaster beside its drum rather than replacing it.
Three questions settle it for most roasteries. Work through them below.
Browsing the other side of that choice? See the used drum roasters collection.
If you are moving on from a machine you already own, we list used roasters for sellers across both formats. Send the details through our sell your equipment form and we will tell you what we can do with it.
Air roasting is a straightforward idea that has held up for fifty years. Float the beans in hot air, heat them evenly, pull the chaff out as it sheds, then cool them fast. The machines are simple, they last, and they give you a profile you can repeat.
Whether that suits your roastery comes down to the cup you want and the space and utilities you have. Match the machine to both, and the format argument stops mattering.
Yes. Air roasting, hot air roasting and fluid bed roasting all describe the same method. "Fluid bed" refers to the way the beans flow like a liquid once the airflow lifts them.
Chemical engineer Michael Sivetz developed the first commercial fluid bed coffee roaster in the 1970s. Sivetz machines are still in use, and they still turn up on the used market.
It tells you the roaster used a fluid bed machine rather than a drum. It is a statement about the equipment, not a roast level and not a quality grade. A light roast and a dark roast can both be air roasted.
People try it, and it is not the same thing. An air fryer circulates hot air around food that stays still. A fluid bed roaster drives air hard enough to lift and churn the beans, which is what makes the roast even. An air fryer also gives you no way to clear chaff or to cool the beans quickly.
Often, yes, and the reason is mechanical rather than magic. Removing chaff during the roast and avoiding scorch marks takes away two common sources of bitter, smoky flavor. Bitterness also comes from roast level and from how you brew, so the machine is only part of it.
Both. The format scales from small countertop machines up to production systems that roast for a full wholesale operation. What changes with size is the install: bigger units need real venting and often a gas supply.
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