Sustainable Design Follows Function

In the Generation 1 the Roastmaster had to lift the beans over his head to fill the Loading Hopper.  Not surprisingly it was not the popular choice but it was the simplest solution.  The Roasting Chamber was pivoted from the Loading/Roasting position to the Dump position where the roasted coffee was dropped into a Cooling Tray.   The SmokEater™ (an efficient form of the After-burner used gas heated roasters) was attached but not an integral part of the machine.   Maintaining seal integrity on the sliding Roast Chamber was difficult and was exacerbated by the strong smoke of the dark roasts.

Generation 2 went through several iterations.  It did away with the sliding Roasting Chamber and overhead Loading Hopper.  The counter top roaster, again with an outboard SmokEater™ had pneumatically controlled valves which were able to route the air so that green beans could be loaded from a counter height Loading Hopper. The re-circulated pressurized air is able to transfer more heat evenly to the beans than the high temperature (often twice the temperature)- low pressure circulated air used in drum roasters because in the fluidized bed all the air goes through the beans without having a portion of the flow simply going around the beans.  This model also introduced the second generation of the Roasting Monitor.

The function of the NXT Roaster is responsible for the form it was given.  In brief, recirculation requires the shape of an "O" which is formed by the two larger columns tied together by the base and top pipes.  The left most small rear column is the Cyclone which removes the chaff from the circulating air while the right most  rear column is the SmokEater™which does the final air cleaning or smoke neutralizing before exhausting the air during the Cool Mode.

Shown above is the third generation 3 kg Roastaire™ that roasted on the exhibition floor at both the Toronto and the Vancouver Canadian Coffee & Tea Shows.  No chimney was used for the 110 batches of green beans roasted.  It was the only roaster that Roasted On-Site and inside the hall.   This version was a "complete re-think" of the functions and the layout of the coffee roaster.  It required the development of a High Temperature Blower capable of fluidizing the green beans, a new computer based Roasting Monitor, PID Temperature Controllers, two Pneumatic Bean Conveyors, initial bean cooling within the Roasting Chamber, and a Packaging Silo to further cool the roasted coffee beans.  The SmokEater™ was incorporated into the Roaster body so that the entire unit could be moved on casters and occupy a relatively small footprint.

The goal was to make the industrial roaster compatible with an urban environment, without requiring optional add-ons, yet be as compact as possible.  To improve the efficiency well above that of a gas burning roaster the air was recirculated.  The post "Roaster Pollution Reduction" shows photographic results, after 5 years of cafe roasting, that the air was cleaned before it was re-circulated to the Roasting Chamber.   This compares very well with the caked exhausts, of other roasters, shown by KaladiCoffee on Youtube.com .  It was not an overnight success but it works well.  The High Temperature Blower required a great deal of development since off the shelf blowers do not survive such temperatures for very long even with high priced precision bearings.  The pressure and flow is required to fluidize the beans which is among the most efficient ways to evenly transfer the heat to the beans.  The wasteful solution has been to move cold air which is then passed through the Heating Element.  Air is continually heated from ambient to roasting temperature.  The wasted energy is augmented when the Pollution Controls are implemented. The NXT Roaster only exhausts air for 75 seconds of the 10 to 12 minute roasting cycle,  During this phase the air is further cleaned, as shown in another photo in the already mentioned post.

The Computer based Roasting Monitor makes it possible for the Roastmaster to monitor the pyrolytic process to consistently and repeatedly attain the required degree of roast.  There will be another post along with annotated pictures of the program's screen view in a further post or maybe posts.  The Roasting Monitor clearly shows the the pyrolytic reaction is stopped within seconds, minimizing the roasting overshoot which allows the Roastmaster to "call the roast" for its degree rather than for what it will be in 60 to 90 seconds. Which is the time some units take to dump the beans, fill the bottom of the Cooling Tray, then turn on the Cooling Fan.

The PID ( Proportional Integral Derivative ) Temperature Controllers do not click Off/On as the temperature passes through the set point but rather the algorithms analyze the rate of temperature change to anticipate, with accuracy, reaching the temperature set point.

The Loading Pneumatic Conveyor allows the Roastmaster to fill the counter height Loading Hopper with 3 kg of green beans rather than the too common overhead hopper.  The Green Bean loading takes place at the same time as the roasted coffee beans are conveyed to the Packaging Silo then cooled for several minutes.  Typically this silo is positioned in the packaging area above the counter, shown in a photo from the Canadian Coffee & Tea Show booth.

Fresh Cup Roastery Café booth   (well, half of the booth)

There is no visible exhaust to show how effectively the Pollution Control System is.  We have reached the level of requiring sniffers and gas analyzers.  The electric elements obviously do not create combustion gases which, in gas fired drum roasters, are circulated through the coffee before flowing to the chimney.  Afterburners, for gas fired drum roasters, with a comparable output to the Roastaire™ range from 400,000 btu to 1 million btu which significantly increases the energy costs of each pound roasted.  Such a waste.  Perhaps an operational cost comparison blog is in the offing. 

Nano Roasters ( coffee roasting intro )

Though I use these small 100 to 250 gram roasters at home or to quickly sample some green beans I do not find them practical in a commercial setting.  In a cafe a micro roaster with a 33 lb/hr capacity is more practical, gives more consistent results and has cheaper operating costs per pound of roasted beans.  The nano roaster will roast a small batch of green beans cheaply, show you the advantage of freshness, and will encourage exploring various roast levels.  In this Blog I prefer to focus on Cafe On-Site Roasting with the 33 lb/hr (15 kg) Micro Roasters.   These will be examined under various titles in other posts.  This post looks at an inexpensive introduction to coffee roasting.

The tiny roasters are often the realm of the adventurous who are doing this at home or because they wish to explore a new freshness dimension for their product line.  Of the "at home group" usually only the truly passionate for Freshly Roasted Coffee will continue to roast after the novelty wears off.   At first impression the nano roaster is an inexpensive roasting introduction especially if a buyer ignores that they are light duty machines.  A small roaster requires as much supervision as a micro 33 lb/hour machine.  Therefore the greatest cost becomes the labour per lb roasted.  Let's say that gathering the information is important and that lower margins, at this time, are secondary.

Many small roasters are designed more for selling than great roasting.  That nice glass container gives the buyer comfort but no one puts a "Clean me Regularly - when cold" sticker on it.  Windex works quite well but I would at least do a finishing wipe with alcohol unless you really like the Windex flavour (I have not used Windex inside the Roasting Chamber but thought there should be a caveat).  I have yet to see a home-style coffee roaster with pollution controls.  They just get away with it because of their small batch size.  It is not "green" roasting and it actually wastes most of the energy because the air is heated then ejected.  Some people have the romantic idea that there will be a coffee aroma wafting through the room.  Wrong!  Think more in the line of many simultaneous burning toasts, hence the vented fume hood.  Roasting outside is often problematic  because of the temperature differential required to reach the roasting temperature.  On colder days the small electrical heating element may not have the capacity to sufficiently raise the temperature of the air entering the Roasting Chamber.  It is possible to increase the heat by slightly closing some of the louvers.  Don't overdo it or you reduce the capacity of the roaster or even worse melt the fan or burn the motor.  All this means the roasting strategy should incorporate a fallback option or a forgive me clause, "I was wrong" so that you can try again.  

In choosing any roaster I would say that heating/cooling the beans evenly is most important.  There are ways to do that but it is a real challenge to do that with a normal household electrical circuit. I prefer the air to do the mixing because it will also push the air through the beans to heat more evenly.   If the beans are shooting up like a fountain the air is not evenly heating the beans.  So called automated Roast Controls should be only counted on to give a rough guide.  Coffee Roasting is a chemical reaction that has many inputs.  When the beans' requirements are fulfilled the reaction will start.  The problem, of most if not all nano roaster controls are unable to integrate the variables or inputs that affect the roast.  Voltage fluctuations affect the heating element and the fan therefore it is not an ideal time to roast when power consumption is high i.e. meal times.  Green coffee beans are living seeds that absorb humidity which must be evaporated at the beginning of the roast.  Humid conditions presents a double whammy because the beans have a higher moisture level and the humid air is less able to carry it away.  Ambient temperature affects the capacity of the element to heat the air.  Too low and the beans will be baked.  Higher altitude and low barometric pressure will also reduce the heating and mixing efficiency but it also lowers the boiling point of the moisture.  If the roaster is hot from previous batches less time will be required.  In an analysis of a database of thousands of roasts we found that the start of pyrolysis (the chemical change caused by heat starting at a bean temperature of 190 to 205°C according to different sources - the phase where sugars are caramelized ) can vary over 1.5 minutes for the same bean and degree of roast.

The first thing is to develop a plan based on advice from existing roasters.  I have reservations about calling the sales pitches - useful advice.  Potential difficulties are related to capturing chaff, diverting the smoke, and cooling exothermic beans (yes they get that hot).

Before posting this there was a little trip through blogland to see what was written.  The worst suggestion is the frying pan method because there is only a point of contact between a surface curved on two axes and a flat surface which means the bean is overheated on the point of contact and under heated elsewhere.  The street vendors in London have figured this out so they roast chestnuts in hot sand for more even roasting.  Popcorn poppers do not cause condensation on the beans - the temperature is well above boiling point.  Don't spray water to cool the beans and to make up for the weight loss during roasting.  Remove some beans from the popcorn popper if the batch is not mixing at the beginning because the bottom layer will quickly scorch.  Have a look at a previous post "Not Sustainable Roasting" for anecdotal evidence that companies don't always understand this process.  If there are unclear statements or questions just leave a Comment.

Better roasting was achieved with the no longer in production Popcorn Pumper because the Mabuchi motor drives the fan blade at a higher speed.  We no longer find these in stores but they are found "used good outlets" such as Goodwill, St. Vincent de Paul, Value Village etc.  The Popcorn Pumpers sell for $2 to $7 and often little used.  Generally I buy them for the motors because the solid bronze bearings do wear too quickly.  It is possible to remove and install the Impellers but push the Shaft out and support the Shaft at the back of the Mabuchi when pushing the Impeller on.  The 24 VAC transformer has lasted 25 years but there has been at least 15 motor changes because when the bearings are worn the speed decreases which lowers the capacity it can handle.

In reconsideration, this may be overwhelming, it is easier to just do it, after planning the cooling process.

NOT Sustainable Roasting

Today I received a Drum Roaster's Newsletter which was interesting since I would have thought that they know the topic of coffee roasting thoroughly.  The first sentence informed me that drum roasters haven't really changed over the years.  That does give the impression that there is more interest in marketing than innovation.  As an outsider I think they should be devoting a lot of resources to curbing their energy waste.  Using a 400,000 btu to 1 million btu Afterburner on a relatively small coffee roaster is wasteful.  Perhaps it was innovative decades ago but the improvements since then have hardly been ground shaking.  That leaves only marketing spin such as writing that the drum roasters are for those that enjoy their artistic side of roasting.  Never quite thought of it that way, but I can understand that with one of those Afterburners the Roast Master would not want to dwell on the accounting side of roasting.  So much heat is going up the chimney that a costly high temperature stainless steel chimney is required.

Apparently, so it says, "You can’t roast fast and dark at the same time without risking an exothermic reaction — you have to slow down the entire process to fully develop the flavor of the beans."  The first half of the roasting process is endothermic,the bean is absorbing heat to evaporate the moisture.  The steam pressure, I am told, swells the bean before escaping into the surrounding air. To recap; beans swell and the beans lose the weight of the evaporated moisture ( varies with humidity and darkness of the roast) which results in a significant decrease in density.  The bean temperature then increases more rapidly because the moisture is essentially gone.   Pyrolysis, it is written, occurs in a oxygen free atmosphere which describes the interior of the bean.  It is during this time that there is a caramelization of the sugars.  This reaction is exothermic therefore it has to be monitored closely in order to stop it at the proper moment with a lot of cool air.  The high temperature of the drum roaster air is required to convey the required energy because the air only meanders through the beans.  That results in a rapid decrease in air temperature  as the first layers absorb most of the heat because of the large temperature differential.  The danger here is if the bean is exposed to more heat than it can absorb there will be some burning of the outer layer especially if there is a large temperature differential and/or significant conductive heating.  Mixing the beans attempts to average the amount of heat absorbed by the beans.  One of the challenges is "calling the roast" when the circulating air is about 300°C hotter than the starting point of the exothermic reaction ( above 180°C according to R.Eggers and at 200°C according to Clarke & Macrae).  When coupled with using the Bean Sampler to establish the level of the roast plus the time required to dump the beans into the cooling tray it is understandable why many roasters are still very stressed  by the experience even after they have been roasting for nine months.  An appropriate analogy is shooting ducks; the expert hunter aims for the position where the duck will be when the buckshot arrives.  For various reasons a lot of people have a problem with duck hunting.

Like a typical chemical reaction the bean waits for the input conditions to be satisfied before it "goes exothermic".  If voltages (or gas pressure) is lower, ambient temperatures are colder, humidity levels are higher it will take longer to reach the trigger point.  A very light roast can be stopped but it will be classed as "not fully developed" and not considered optimal.  If the air/vessel temperature is too low the bean will be baked rather than roasted.  An interesting aside is an experiment done in the 90's (unintentionally) where the beans were baked then the oven was shut off without force cooling them, about  20 minutes later there was an exothermic reaction that created a mushroom cloud at the 18' ceiling.  It was sort of induced or at least encouraged spontaneous combustion.  

Perhaps one of the reasons why it is suggested that the roasting process has to be slowed down is that their roaster cannot transfer the heat to the beans any faster.   Air has a low thermal density and if it only moves slowly through the beans by convection it is not very effective at heating beans.  Increasing the temperature will scorch the outside before the inside is hot making the mixing action all important.  In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C.  The high temperature cooking analogy for beans hit by the super hot air is frying eggs while using the stoves highest heat setting.   To this end the Roastaire uses a fluidized bed in which 240°C (adjustable as required) air is pushed through the beans.  This significantly increases the heat transferred to the entire batch of beans.  The beans have a limited ability to absorb the heat therefore the temperature gradient is more uniform throughout the batch with the forced air stream.  The added benefit is that the air flow continually churns the beans and carries away the chaff.

Another marketing spin of the drum roaster claim that it is advantageous that 15% of the heat is transferred to the beans via conduction.  This can be bean to bean contact but the text specifically says "The beans stay in constant contact as the drum turns..." which in my experience is the main cause of tipping.  In" Coffee Technology Vol. 2" Clarke & Macrae write "Decreasing air temperatures and decreased proportion of conductive heat is a feature of recirculatory-type roasters ..." 

Reading the newsletter is good training for critically reading the newspaper.

"Green" Roaster

Pollution controls is a timely topic but it was not at all planned for right now, another example of serendipity.  We are currently upgrading Mel's ( freshcup.ca ) third generation Roastaire™.  It is only five years old but enough new parts were developed in the interim that it was a good idea to modify or install parts to satisfy his working requirements.  The first occasion for an "Ah Hah!" moment was the inside view of the exhaust just before it enters the chimney.   It was a good feeling to have the proof that the "SmokEater™" was working so well.

The second element in this synchronicity is the chimney fire warning contained in two advertisements in the September - October  "roast Magazine":

- If you're a roaster, you know the quote: "It's not IF you're going to have a roaster fire, but WHEN."

- "According to the U.S. Government, there were over 1,800 roaster fires last year." an advert by Iron Dragon Tools

They were advocating regular exhaust and chimney cleaning to prevent chimney fires yet the Roastaire™s roasted for over a decade without cleaning an exhaust nor having a problem.  Furthermore, only days before we had witnessed a five year old Roastaire™, which roasted 5 days a week,  that had an exhaust which was as clean as the day it was installed.

Further reading of "roast Magazine" showed the significance of the problem where their featured interviews asked each interviewee about their experience with fires.  Youtube has some videos of the chimney coating problems faced by other roasting companies.  Mel was deprived of this experience but he does not mind.

Originally our pollution test was only a visual inspection or rather the lack of visual evidence at the chimney when the Roastaire began the Cool Mode.  The test is more stringent now but we did not have to make any changes to the roaster.  Obviously a clear exhaust cannot be deemed to be a definitive pollution test after all we know that the common solution to neutralizing the smoke is to subject it to the high heat of a natural gas flame.  Small independent roasters do not have the required scrubbers to clean the combustion residues but they do eliminate the roasting smoke.  You still have to ask "Is the 400,000 btu to 1 million btu flame in the Afterburner the best way to eliminate smoke?".  It seems to be very wasteful to me not to mention the pollution by that flame itself.  In addition to its costly fuel charges the gas Afterburner takes up valuable floor space.  We decided to make the SmokEater™ a standard component of the roaster to optimize its operation and to minimize the footprint.  It does create a more expensive basic unit but we don't foster midnight roasting unless it is the third shift.  Of course not having to pay the gas heating for those high input Afterburners means that savings accrue very quickly.

Another fundamental difference with Drum Coffee Roasters is that they are continually flowing air through the flame, through the beans, and then up the chimney.  The Roastaire™ is a closed loop system for the entire Roast Mode.  During that time the air is recirculated which has the added benefit of significantly increasing the heating efficiency.  The air cleaning process wasn't an easy problem to solve.  Leaving too much smoke in the circulating air can affect the taste of the coffee by coating the beans with a tar like substance plus coating the inside of the roaster with the same substance.  Below is a photo of the air duct just before it enters the Roasting Chamber.  After 5 years of roasting there is only a light staining of the interior of the duct.

A design choice was to stop the roasting process within the roaster to improve the roasting repeatability.  Our earlier generations used a cooling tray, which is easier to accomplish, that delays cooling until the transfer is done and evenly distributed over the bottom.  Cooling within the Roasting Chamber permits the constant monitoring of the air quenching of the beans which stops the exothermic roasting reaction within a few seconds.   It also assures that the air entering the roaster during the Cool Mode will be "double cleaned" before it is evacuated to the vent or chimney.

California is the bellwether on emission standards but it is still a work in progress.  The traditional method has been complaint based forcing many roasters to occupy commercial areas or midnight roasting.  The people at Roastaire™ promote the "theatre of roasting" which takes place at the café.  It is the most convincing way of communicating to clients that the coffee is "freshly roasted".  To this end they roasted, without a chimney, on the floor of the Canadian Coffee & Tea Shows in Vancouver and last year in Toronto.  

In closing here is a quotation that appears in the October 26, 2011 edition of the Edmonton Journal Food Section which describes one side effect of the technologies we supersede.

“When we moved from our old location to this new location, the first couple of months we roasted coffee, I saw the fire department four times because people driving by would see all the smoke from the roaster coming out of the roof, and they thought the building was on fire,” says Filpula, laughing. “The firemen would come in; I’d give a tour of the roaster.”

Sustainable Roasting

During the last decade we have been quite busy "doing" rather than writing about our goals.  Vancouver was the second Coffee & Tea Show in which the Roastaire™ was the only coffee roaster that was making magic in the hall.  In time, we should blog some of the fundamentals that drive the project i.e. efficiency, pollution controls, sustainability, "greeness", freshness, design, roasting, etc.

For more detail click photo and choose original size

 Function determined style for the roaster and the business model.  FRESHNESS is our dominant theme.  It, along with SUSTAINABILITY  has determined the roaster design and the business model.

No one involved had the desire to operate a roasted coffee warehouse.  For those who may not have given it much thought the green beans have a relatively long life span, just as other living seeds.  Given proper storage conditions they last more than a year. 

Roasted coffee has a short life span.  This is incongruous with the designation of non perishable food.  It has been written that lobbying by food purveyors resulted in a legislation that roasted coffee has a lifespan of greater than 18 months hence it was deemed non perishable.  The coffee continues to stale along its own time line but the vendors do not have to indicate when it was roasted.   Many gimmicks are used to give the impression that freshness is maintained or is not important.  Valves do not "lock in freshness" they prevent the carbon dioxide, given off by the recently roasted beans, from bursting the bags.  Cold storage does reduce chemical reactions but studies promoting this used temperatures that were much colder than the inside of a household deep freeze.  Furthermore, bar the bath tub, the refrigerator is the most humid place in a house.  It is not a good bean storage environment.  Moving beans between the cold storage and the coffee preparation counter only exacerbates the problem.  Grinding the beans at the time of purchase is most likely the worst practice.  Store ground beans are probably better than going without but you deserve so much more. 

The aim of getting the coffee to the consumer within 3 - 5 days has determined the size of the roaster and the business model.  People have found that the optimum flavour is produced 24 to 48 hours after roasting.  With this in mind   www,FreshCup.ca   opened an Online Store which ships coffee on roasting day via Expedited Parcel.  There is no compromise possible on shipping - it has to be as fast as possible.  To make the Expedited Parcel costs acceptable they are free within Canada for two lbs. of coffee, or more.  To present the consumer with a top notch product all elements of the preparation have to attain the same high level.  Giving someone the choice of saving a dollar with a snail like delivery was thought to be counter-productive.

It is getting quite obvious why this opinion was not a tweet.

The Roastaire™ has a 3 kg green bean capacity which yields nearly 6 lbs of roasted coffee depending on the degree of roast.  The darker the roast the greater the weight losses.  This roaster is able to do about 5 batches per hour, again depending on the degree of roast.  This implies that a café only needs to roast what is required in the immediate future.  The concept is "store green beans" and "move roasted coffee".   Regarding the café owners; they will pay for a coffee roaster regardless, either it will be their own or that of a supplier.

Even though we have reason to believe that our roaster produces excellent coffee I think that you can be well served by a local roaster if your coffee is freshly roasted On-Site.

Canadian Coffee & Tea Show

We just returned from the Canadian Coffee & Tea Show, in Vancouver, where the Roastaire™ roasted coffee on the show floor.  The big deal was that it was the only coffee roaster that took on the challenge of roasting inside without a chimney.  A lot of design work has gone into improving the roaster efficiency and pollution controls but that is what made it possible to accomplish task.

The air, cooling the newly roasted beans, was vented into the room so there was a coffee aroma near the booth but the roasting smoke was neutralized within the machine which is why this machine is friendly to neighbours.

 Mel, the Roast Master, roasted approximately forty 3 kg batches of coffee while he explained  the Roastaire™ features and the significance of monitoring the roasting process in real time with the computer.  The Bean Sampler was only pulled to show the visitors that there was a Bean Sampler but that the process was not optimal especially for someone with less than a year's roasting experience.

Mel's coffee is available at FreshCup.ca   There are no transportation costs within Canada for two or more pounds of coffee.  Unfortunately this morning's order from Santiago, Chile could not be filled in a timely manner.  FRESHNESS is their mantra.

We also received the Twitter Lawrence Tanner who has a better photo of the Roastaire™ on yfrog:  (link is   yfrog.com/kgrh6dkj  ) as shown below

LT_Chronicles Lawrence Tanner

Nifty ecofriendly on-site coffee roaster #greentech #coffee www.roastaire.ca & www.freshcup.ca cool organic beans! yfrog.com/kgrh6dkj

3 Oct 

 It is quite a challenge to photograph stainless steel cylinders in front of a black wall.  There is certainly something to be learned in that process as well.

Roastaire™ and Coffee Roasting