I love this forum about wood roasters. I own a 1 kilo electric drum roaster called a Torrefattore. It sounds Italian but made in Isreal. I paid for it many times over by roasting for a friend of mine who owned a couple restaurants, but alas he retired. I love the roasts I get from it, but it is limited in that the heating elements cannot make instant changes as with gas. As for my own roasts, I simply roast 1/2 a kilo and can achieve second crack in 6 to 8 mins depending on the weather, as I roast in my garage. Currently I am going through a bag of Sumatran Mandheling.

I have recently purchased a pellet stove for my new home followed by a Traeger Pellet Grill. I live in Oregon where both were invented. I am fascinated with both. As I watch these machines work, I think of roasting coffee with wood pellets. The BBQ pellets are spendy, but you could either use a direct or indirect method of heating the beans as the pellets are approved for food use. Hummmm? As for the heating pellets, they are supposed to be a no no in pellet grills as some manufactures use binders if their machinery is not capable of the 100 tons of pressure necessary to liquify the Lignin in the wood and create a Premium Wood Pellet. Call me crazy, just don't call me late for dinner if it's cooked on my pellet grill.

I think that there is big difference between cast wooden stove, or massive brick build wooden stove that provides heat for roaster and camping barbeque (or fireplace). The massive wooden stove has fairly stabile temperature. One loads the stove, wood is being burned quickly, heat is stored in storage and released gradually. For example, Tulikivi stoves have predictable temperature output for 12h or even 24h.

Pellet heating stoves would behave similar to gas, or heating oil. In fact, for heating purposes, wooden stoves do have some kind of heat storage (water, bricks, cast iron, ...) while pellets stoves can operate without.

In order to operate wood burning roaster (in predictive manner), the roaster has to have large mass (I mean the burning part). For example, Ballestra 5 Kg batch roaster weighs 500 Kg.

I wonder if this large mass is not main contributor of alleged difference.

Years before I had an espresso machine I used to order whole bean espresso blend coffee from "Mr. Espresso" in Oakland CA (this was also pre-Web days and I had to fax my orders to them as E-commerce had not yet appeared). They did and still do roast with wood. I recall the coffee being far superior to what I could buy locally at the time but I was doing strictly Melitta pour over and had few reference points (this was in the early 1990's).

More recently I had the opportunity to sample some aged Indonesian coffee (varietal unknown to me) from Aroma Coffee in Bandung Indonesia. They are a fairly high volume roaster that roasts exclusively with wood on a rather ancient German roaster. The coffee was good but it was an aged coffee (as so many of their offerings are) and just as with the Mr. Espresso beans - I had no valid A/B reference point.

I can state with confidence that in both cases that there were no overtly smoky or woody notes in the flavor profiles. The smoke that gets re-absorbed into over-roasted beans from the Green Giant and others lends a very distinct (and typically unpleasant) smoky or burnt flavor that I did not detect in my limited sampling of wood roasted coffee.

If I recall correctly one of the key claims Sivetz has is not just related to burning chaff but his contention that the subtle aromatics of good beans are masked by smoke re-absorbed into the beans when drum roasters are used - in theory because they don't have 100% constant through-flow of air and also because they use a mix of conductive and inductive heat.

I spent three years roasting on a Sivetz 1/4 bagger and have now been working (albeit a bit less frequently) doing small batch (e.g. 5 to 7 pounds) roasting on a Diedrich IR-12. I believe there are benefits to the Sivetz method but for reasons different than what he claims. I also believe there is a higher risk of smoke re-absorption in drum roasting but that's easily controlled with good modern roasters.

More salient - for this topic at least - is that a roaster with easily controlled airflow and precisely controllable heat levels makes it far easier to avoid unwanted artifacts in the flavor profile and also increases the likelihood that a specific roasting profile can be developed that optimizes sweetness or other characteristics of a specific bean - and that the profile can be repeated (assuming it was properly documented with detailed roasting logs).

Can stellar roasts be done with wood? Absolutely yes - but it will require far more diligence on the part of the roaster and be less likely to be easily repeatable for those trying to tweak for certain flavor profiles. If I were to roast with wood I'd want a way to raise or lower the heat source (or the drum) that would provide some measure of heat control and would also want very precisely controllable airflow.

With optimal batch size - which is 20 pounds on an IR-12 (at my 5 to 7 pound batch size I am challenged by control issues) - the "Diedrich method" dictates that the flame is kept at a fairly constant level and that profiles are controlled with airflow. I think one of the biggest pitfalls of drum roasting is the potential for tipping during the early stages of the roast and it will yield a flavor artifact that would far overshadow most that would result from the type of heat source.

It's probably romantic nostalgia talking... but one of the best cups of coffee in my memory was the first time I had coffee in an Ethiopian restaurant - where they roasted the beans in a dented beat up old fry pan on a gas range, crushed them with a mortar and pestle and steeped in a clay pitcher of hot water before serving.

Sometimes it's not about the tools but as a roaster I appreciate and benefit from having a technologically advanced and precisely controllable tool to help me develop and evolve in my craft.

Phaelon56 wrote:It's probably romantic nostalgia talking...

And that, folks, sums up my opinion about "wood roasted coffee" in a perfect sound byte.

The combustion gas and air flow discussion has been split off.

another_jim wrote:The combustion gas and air flow discussion has been split off.

What took so long? I thought Jon was gonna have a heart attack.

AndyS wrote:What took so long? I thought Jon was gonna have a heart attack.

Shoot - I almost did! Thank gawd y'all came to your senses....

Whale wrote:And as Jim has already mentioned, there are Quest M3 owners making mods to the air flow of their machine so possibly one could artificially introduce "wood burning combustion gas products" into the air inlet of a M3 and thus simulate the effect of wood burning into an electric roaster.

But what if the main "effect" of wood-fired roasting is from using wood fire as the heat source?

After working with a wood roast compared to a gas roast of the same bean I am starting to believe that the change in heat application (profile and control) may be the primary difference (and not the wood smoke). When I started roasting, I quickly learned that smoke is a part of the process no matter what your heat source is.....so I am skeptical about smoke from wood fire really being the difference.

It should be feasible to throw wood chips in with the beans, just as one does when smoking in an oven. My hesitation is that it might mess up the drum surface; although that would nail down the proof that there is a difference. The oldest home roasters were basically sealed tin cans on a spit over a gas flame. Having a throwaway roaster of this kind, and a regular roast to one with wood chips may be illuminating.

From Mr. Espresso in Oakland, California:

. . . Finally, we slowly roast each bean variety separately over an oak wood fire and only afterward do we blend them. The care we take at each step along the way makes for an extraordinarily good coffee.

For their take on oak, check out Oak Wood Roasting . . .

Cheers,
Jason