Photo from Japanese Coffee Co.

Originally Posted On: What is Special About Charcoal Sumiyaki Coffee Roasting? – Japanese Coffee Co.


You might be wondering what ‘roasting’ means in a literal sense but put simply, it is just like ‘baking’ coffee beans. This might come as a surprise to many but coffee beans grow inside beautiful red cherries. Once these cherries have been harvested from the coffee plants, the unwanted parts of the cherries such as the skin and pulp are removed and as a result, we get fresh green coffee beans!

The green coffee beans in their raw form are far from ready to be made into a delicious cup of coffee. This is where the crucial process of ‘roasting’ comes into the picture. Due to the process of ‘roasting’, the coffee beans become ready to be brewed by the addition of hot water. The result of this is the delicious, aromatic, and almost magical drink that many of us know by the name ‘drip coffee’ or ‘pour-over coffee’.


Now that we have a basic idea of what the roasting of coffee beans means, let’s dive a little deeper into the fascinating world of coffee roasting. The coffee roasting process can be roughly divided into two major types. What is interesting is that the taste of the coffee is dependent on the type of method used for roasting.

The first type is called “Hot Air Roasting” and as the name suggests, it is a method that uses high-temperature air to roast coffee beans. To have a mental image of what it is like, we can think of it as roasting the beans using a dryer that gives out fairly hot air. Coffee beans that are roasted using this method tend to result in light-roasted coffee.

The second type, called the “Direct Fire Roasting” is a method where the coffee is roasted using fire from a gas burner. This can be compared to grilling meat on a barbecue. This type of roasting tends to result in darker roasts and gives the resulting coffee a stronger taste.

Picture of a coffee roaster


The “hot air roasting” and “direct fire roasting” have been the two predominant types of roasting in the world of coffee but an exciting, third type of coffee roasting has emerged and is quickly gaining popularity. Let us introduce you to – Charcoal roasted coffee. As it is evident from the name, this method uses charcoal as a heat source to roast coffee beans.


Picture of binchotan charcoal

One of the biggest advantages of using the charcoal roasting method as opposed to the other methods is the effect of Infrared and Far Infrared Rays. Some of us might be already familiar with new types of rice cookers, since they are so trendy nowadays, that uses a similar concept to charcoal grilling. Due to the effect of Infrared and Far Infrared Rays, the coffee beans are cooked deeply from the inside and the resulting roasted beans have a plump and fluffy finish.

Besides, charcoal roasting has the effect of slowing down the deterioration rate of coffee beans. The deterioration of coffee beans can be described in simple terms as the loss of flavor, taste, and aroma of the coffee, which we are all familiar with, and want to avoid or at least slow down at all costs. This happens because the moment the coffee beans come out of the roaster, the beans start to undergo oxidation due to the surrounding air. The good thing about charcoal roasting is that when charcoal is burnt, it gives off a large amount of Carbon monoxide. This Carbon monoxide delays the oxidation process and as a result, prolongs the shelf life of roasted coffee beans.

Picture of roasting

Picture of Charcoal Coffee Roasting

Not only does charcoal roasting protect the coffee against oxidation, but it also gives the coffee a unique flavor that would be unattainable through any other method. Anyone who has used charcoal for cooking would be familiar with the sheer richness of aroma and flavor that can come from charcoal grilling. Coffee beans that have been roasted using charcoal carry the aroma of charcoal, which can be described as the perfect balance of sweet, smoky, and savory. Hence, charcoal-grilled coffee tends to have a strong taste and would be highly regarded by anyone who loves a coffee that is smoky, rich, strong, and savory.


The traditional roasting methods have been well established as a tried-and-true method over time. Compared to those, the charcoal roasting method is quite time-consuming and can be expensive as well. Then why do we still prefer the charcoal roasting method?


One of the most important aspects of roasting coffee beans is the removal of excess water from the beans. If the water is not completely removed through roasting, the remaining moisture within the coffee gives it an unpleasant smell and acidity. To effectively remove moisture from within the coffee beans, it is crucial to transfer heat to the core of the beans. One of the things that charcoal grilling does very well is to transmit heat directly to the core of the beans, which in turn removes any unwanted taste or flavor profiles from the resulting roasted coffee.


Far Infrared rays are given off when charcoal such as Binchotan charcoal is burnt ( Binchotan is a type of activated charcoal that is traditionally used in Japanese cooking and is also known as white charcoal). Far infrared rays have the property of being easily absorbed by substances other than metals. This tendency of Far Infrared rays to be easily absorbed by the coffee beans makes the heat reach the center of the beans, resulting in plump coffee beans that are baked uniformly throughout its body. As we can imagine, when each bean has been uniformly baked with a fluffy finish, a cup of coffee brewed from this roast would have a balanced, well-rounded taste and flavor profile, as well as a smooth mouth-feel.

Adding Charcoal to Charcoal Coffee Roaster


The biggest difference between gas-burner roasting and charcoal roasting of coffee is the absence of Far Infrared rays* in the former and the presence of Far Infrared rays in the latter.

Far Infrared Rays: Far Infrared rays are electromagnetic rays that lie between visible light waves and microwave (the waves used in microwave ovens). These Far Infrared Rays have the effect of heating up substances from within by making the water molecules inside the cells.

As we have read earlier, the most commonly used coffee roasting machines use gas burners as heat sources. Inside these machines, coffee beans are heated only on their outer surfaces, which makes them vulnerable to having differences in the level of roasting between the inside and the outside surfaces. Therefore it is common for roasters to set the roasting temperatures higher when using gas roasters in an attempt to make the heat reach the insides of the coffee beans. A common problem, which is not so difficult to guess, is that in this method the outer surface of the coffee beans can easily get over-burnt. This unwanted result can easily happen using gas roasters anytime a roaster tries to produce a roast profile that is darker than a medium roast.

A coffee roast like this, when brewed, will give off an unpleasant sourness. Also, this batch of coffee will have all of its wonderful chemical ingredients decomposed, losing its original quality, making it impossible to produce any depth or complexity of taste, flavor, and aroma. From a coffee connoisseur’s standpoint, this is an absolute tragedy! Many of us who regularly drink coffee must be familiar with the impression that darker and bitter coffee tends to have a simple, clean taste with minimum complexity. However, take this darkness one notch higher and you will get a coffee that has a putrid, burnt smell and leaves an extremely bitter aftertaste that torments your palate for a good while.

Temperature differences between gas and charcoal roasting

Temperature differences between gas and charcoal roasting

Now let’s take a look at the scenario in the case of charcoal roasting and appreciate how different it is from the traditional method. In the case of the charcoal roasting method, the outer surface of the coffee beans can be roasted by “the heat generated from charcoal”, and the inner surface of the coffee beans can be cooked by the “heat generated by Far Infrared rays”. These two processes of heating the outer surface and the inner surface of the coffee beans happen simultaneously and Voilà!

This results in a coffee roasting process that can not only occur at a lower temperature than the gas burner process but within a shorter period of time. This also means that it is easier to control the heat reaching the outer surface and the inner surface of the coffee beans, and therefore the overcooking or “burning” of the coffee beans can be avoided easily.

This in turn helps to preserve the special chemical ingredients within the coffee beans so that they don’t lose their originality. Since the coffee beans are able to retain the ingredients that give them their unique flavors and taste, when charcoal roasted coffee is brewed, it results in a full-bodied, well-rounded cup of coffee with richness and depth in flavor, taste, and aroma.

Moreover, as the heat can reach the core of coffee beans easily, the acidity or “sourness” of the coffee tends to decrease. There is a clear difference between the levels of sourness between a medium roast made using the gas-burning method and the charcoal roasting method. Also, unlike gas roasting, which can only be controlled using a valve, charcoal roasting has a bigger scope of adjustment. However, this adjustment is not easy and requires a high level of expertise. Depending on a roaster’s knowledge and skills, the path taken by the fire in charcoal roasting can change slightly on each roast.




  • It is suitable for relatively light to medium roasting.
  • The level of heat in the roaster is not difficult to fine-tune and therefore is easier to keep the roasting finish consistent.


  • It takes away the depth of taste and minimizes the richness of the coffee when it is used for medium to deep roasting.



  • It is suitable for relatively medium to dark roasting as it preserves the inherent qualities of the coffee.
  • In addition, since it is less likely to “burn” the coffee, it is less likely to add excessive bitterness.
  • This is what leads to a coffee that is full-bodied yet mellow.


  • Since it is difficult to adjust the thermal power, the level of expertise and technical skills of the roaster has to be considerably high in order to stabilize the roasting. Also, the acidity seems to be weakened even in the case of light roasting.


Binchō-tan is a type of activated charcoal (also known as white charcoal) that uses oak as a raw material. Interestingly, the word “Binchō” came from the name of a person called Bichū-ya Chōzaemon. He was the pioneering craftsman from Tanabe city, Kinokuniya, who first started to sell this charcoal he made from Ubame oak, which has since been called after his name.


Picture of Kisyu Binchotan

The three major producers of Bincho charcoal are Wakayama prefecture (producing Kishu Binchō-tan), Kochi prefecture (producing Tosa Binchō-tan), and Miyazaki prefecture (producing Hinata Binchō-tan). Among them, the Binchō-tan that uses Ubame oak as the raw material is known to be the best.

Click here to read more about Binchotan


Binchō-tan charcoal is a special kind of charcoal in the sense that it does not have moisture content. Moreover, it has a chemical structure that makes it hard, and difficult to ignite. As a result, once it is ignited, it can generate a large quantity of heat and can reach an astoundingly high temperature – as high as 1000 ° C. Charcoal roasting is one of the roasting methods that require a high level of expertise and experience to master as it is difficult to maintain constant thermal power. However, when it comes to Binchotan charcoal, a relatively stable roasting can be performed as Binchotan charcoal has a high calorific value, long burning time, and gives out a high level of Infrared rays.


Sadly, yes. By this point, we have come to know a lot about the wonders charcoal roasting can do for coffee, and how preferable it is as an emerging roasting technique. That being said, negative opinions about charcoal roasting are not non-existent. The most typical complaint regarding charcoal roasting is that the adjustment of thermal power, which is an indispensable factor when it comes to roasting, is difficult to perform using the charcoal roasting method. Coffee roasting is neither a simple scientific reaction nor a purely technical method. It would be more appropriately described as a delicate combination of art and science that requires the roaster to have a subtle artisan-level sensory flair. Since it is so difficult to control the roasting conditions using charcoal roasting, compared to the hot-air method and gas burner method, many argue that charcoal roasting is not suitable for coffee roasting, to begin with.

And above all, the problem with charcoal roasting, which cannot be ignored, is its high cost. Compared to the traditional roasting methods, the charcoal roasting method has a much higher fuel cost. In addition, the preparation and cleaning up are more complicated in the case of charcoal roasting.

Charcoal Roasting Coffee

Picture of Charcoal Roasting Coffee

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