Roaster Carbon Calculations

The good people at Fresh Cup used the U.S. EPA Carbon Calculator to compare the Roastaire Carbon Footprint with that of a gas roaster.   

A 100 lbs.  of roasted coffee = 1 car off the road for 16 days  

This is how our roasting method impacts the environment. The energy ratio is  2 light bulbs versus the drum roasters 48 light bulbs.  Gas is a cheaper form of energy therefore in dollar terms the approximate heating cost of a gas fired roaster with afterburner is 16¢ per pound vs. the 2.5¢ for the recirculating Roastaire.


Evidently the Roastaire is way more environmentally friendly and cheaper to operate.  


The 100 lbs. of roasted beans represents about 3 hours of roasting, depending on the degree of roast.  Think of the savings to the environment and to the owner.  


It's time for a cup of freshly roasted coffee and a read about selling carbon credits.

High Pressure & High Temperature Industrial Blower

The suggested applications required either high temperature or high pressure but not both.  Googling the terms "high pressure" "high temperature" Blower brings up every type of air mover imaginable.  The designations are quite "loosey goosey" and often stretched so that it will accommodate the particular product being offered for sale.


I expected that this blower rated at 250°C would be at the bottom end of high temperature blowers but no - some units were given the same designation yet could only operate at temperatures that were 100°C lower.  


Some units had operational ceilings that were twice as high as what this one was tested at but their "high pressure" turned out to be .3 psi or 2,070 pascals which implies that it turns relatively slowly.  Low speeds are attainable with off the shelf bearings.  Therefore, it is not a niche that is of interest.


The version pictured is currently on the test bench where it is subjected to high temperature moist air.  Previous tests of off the shelf blowers demonstrated bearing corrosion in less than 100 hours.  It is possible that had it been a continuous test the bearings would have survived longer but running tests that lasted a few hours compromised the bearings too soon.


We are currently using the blower to fluidize and roast beans (coffee and others).  The pressure output of over 1 psi ( 6,894 pascals ) at 250°C  could certainly fluidize denser materials at a lesser depth.  At these temperatures the blower could be the heart of a monstrous pop corn pumper.  With continual introduction of kernels the output will compete with Vesuvius.  Such a machine would have to be brought to corn country Taber for testing.  


A recycled hot air requirement is fundamental to this niche, otherwise it is more efficient to heat the air after the blower i.e. an air knife.  Now, if a high temperature air knife was in a closed system nearly every blower in the marketplace would be inappropriate.


Hot air accelerated drying in an industrial setting would require a moisture extraction process but if it is a recirculated hot air application this is a custom application.  


Have a freshly roasted coffee and think of another application for the unit.

Packaging - Optimism

Packaging attempts to circumvent or overcome the stalling of coffee.   It does not keep old coffee fresh though it is claimed that it slows down the staling for an unbelievably long time.  Most of the advantages are perceived by the consumer based on sizeable advertising programs.  Though it appears that a valve, at least under ideal conditions, lets little air into the bag.  Well, less than the bag would have had when it was sealed.  Vacuum sealing reduces the air and moisture in the bags but that requires more equipment and time.  The valve does let out the CO2 but it also lets the aroma escape.  The vented bag will have a lower internal pressure, than say a metal container.  The lower pressure exacerbates the loss of volatile compounds which are the reason for that olfactory experience.  To circumvent that loss some companies replace the vent by Oxygen and/or CO2 scavengers.

"Espresso Coffee" by Illy & Viani states that the spoilage rate increases by 7 fold with every 10°C increase in temperature.  Unfortunately there is no mention if that calculation starts at absolute zero. It is an unmeasured and uncontrolled variable that very much affects the coffee experience.

A lot of money was invested into the marketing of various types of packages because the business model of central roasters depends on convincing customers that coffee that is more than a year old still has the freshness of yesterday's roast.

I view the valve as a packaging solution which does not contribute much to maintaining the roasted bean's fresh taste.  My only acceptable solution is to buy the freshest coffee from a local roaster.  An exception, in Canada, is Freshcup.ca which ships, via expedited post, the day the coffee is roasted.  On several occasions I have sent some much appreciated coffee gifts.  It could be perceived that I am biased because they use our roaster though I maintain that the long relationship has allowed me to observe closely the organization and witness their commitment to delivering the freshest great tasting organic coffee to their customers.

Do Coffee Bags "Lock in the Flavour" ?

The test will be posted in a few phases, perhaps more if there are leakage problems around the valve, such as the testing apparatus, results, and implications of the findings.

To the left is the inside part of a Check Valve that is incorporated on many coffee bags.  It permits the coffee roaster to bag the coffee very soon after roasting.

For those who may not be aware, freshly roasted coffee releases CO2 (Carbon Dioxide) in the days that follow the roasting session.  The pressure is sufficient to burst bags.  Initially the coffee was packaged in various media such as paper and consequently not hermetically sealed.  Some roasters "aged" the coffee and packaged it several days later when the CO2 had been dissipated.  The Check Valve is a more recent development which allows the CO2 to escape without splitting the bag.  There could be an advantage to this method if the valve is placed such that when the filled bag is stored the valve is the highest point of the bag.  CO2 is heavier than air therefore it will gravitate to the bottom of the bag forcing out the lighter air first.  Technically it is possible that all the oxygen could be forced out in this way.

The purpose of this test is to verify the premise that the Check Valves are more important to the marketing campaigns than to preserve coffee or "locking in the flavour".  Does a valve costing about a penny do the work of precision devices?  If the bag is not hermetically sealed the constantly changing atmospheric pressure will make the bag "breathe" which will introduce oxygen to the contents. 

The apparatus is quite simple and will involve measuring a Control to be certain that the test equipment is leak proof.  The upper left barbed fitting will be connected to a vacuum pump then the valve will be closed.  The Needle Valve is rated at 6,000 psi therefore it should not be harmed by this test.  The vacuum will be measured by water movement in a U tube.  The picture shows two devices that can be sealed to the bag.  The preferred socket is the one to the right which is machined with steps that will fit just over the valve so that it is not distorted or twisted.  This is better than in reality where the valve is pushed by the beans.  Several different sealing materials may be required before a good seal is established between the socket and the plastic check valve.

Plotting the height of the water column should be a good indicator of the leakage rate, if present.

Marketing departments are notorious for making unsubstantiated claims.  Rather than admit error the trend is to spend more money to embellish their fabrication.  Let's check the foundation to the claims.

Freshly roasted coffee does its own marketing.

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The first phase is Testing the bag's Venting Valve in Ideal Conditions.  

The venting valve was cut from a new bag (unfortunately that is a sacrificial test) but a lots of material was left on either side of the valve.  The valve was then mounted to the socket and sealed with a thin layer of silicone adhesive on the periphery.  The adhesive cured overnight. 

A slight vacuum ( 33.5" H2O or 851 mm of H2O) was drawn against the valve.  That is P1-P2 = 67" H2O (1.702 m) in the U tube manometer.

After an hour the water column was 1" (25.4 mm) lower which represents 1.81 cc of water.

After an 2:45 hours the water column was 1.5" (38 mm) lower which represents .165 in3  (2.7 cc) of water.

After an 6:00 hours the water column was 3" (76.2 mm) lower which represents .33 in3  (5.43 cc) of water.

After an 47:00 hours the water column was 9.25" (235 mm) lower which represents 1.022 in3  (16.74 cc) of water.

After an 70:00 hours the water column was 9.88" (251 mm) lower which represents 1.091 in3  (17.89 cc) of water.

Granted the Control Run has not been done.  Under ideal conditions it is little leakage but then it is over a short period.  The pressure, however, is considerably higher than the barometric fluctuations.  So far it can be established that it is not a hermetic seal.  To reflect the packaging role the pressure may have to be reduced, the time period increased, and the valve will have to be pushed against beans rather than held flat in a socket.

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More on a newer blogs Vented Bags Revisited  and Packaging - Optimism

High Temperature Industrial Blower

"Delivering the air with sufficient pressure at 240°C is a challenge that will be addressed in a later post.  Sufficient to say that no off the shelf hot air blowers were found, resulting in another product development." from the earlier post Heating Coffee Beans to Roasting Temperature.


Note:  A fan generally turns slower than a blower and therefore cannot reach the same pressure differential (inlet / outlet).  Fluidizing a batch of coffee requires more pressure than a fan delivers.


The easy, but wasteful, way to circulate hot air is to heat it after it passes through the blower.  This means that all the air has to be heated from ambient temperature to final temperature before it is vented while, if the air is recirculated, only the lost heat needs to be replaced.  The higher the temperature the more efficient the recirculation process becomes.  The advantage is not a few percentage points but rather tens of percentage points.


Our prime interest is roasting coffee which becomes much more efficient when the heated air is recirculated.  No off the shelf unit could be purchased.  Initially we tried then modified an existing name brand blower.  The MTBF (mean time before failures) improved from the initial few hours to over 1,500 hours but the maintenance and problems required a new solution.  The concept was simple but mastering the quirks was not always a linear process.


The designed temperature ceiling for the current model is 300°C but it has only been operated up to 270°C.  Since we did not find this to be an optimum roasting temperature the importance of establishing a higher operating threshold lost its urgency.  There is reason to believe that the upper temperature limit can be raised significantly.


Apart from surviving the high temperature the priority is to develop sufficient pressure to create a fluidized bed so that the coffee beans are evenly heated and continually mixed.  The pressure, while roasting, is just under 1 psi (approximately 6 kPa).  This is the flowing pressure not dead head pressure.  


The current blower configuration is driven by a 3 Hp electrical motor connected to a three phase contactor based motor controller.  The Belt Guard Cover was removed for the photo.


Have a freshly roasted coffee and think of another application for the unit.

Heating Coffee Beans to Roasting Temperature

In cooking the heating process is usually prescribed by the recipe.  Yet, there are reasons why certain chemical reactions are promoted by heating method and temperature.  Common sense tells us that a Blow Torch is not a good heat source for warming the body.  The high temperature differential means that the outside layer will burn before the inside is warm.  Perhaps the Blow Torch salesman would suggest that the body whirl like a Dervish near the flame to distribute the heat.


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.


Considerable research has been done to understand the dynamic and continually evolving variables in the coffee roasting process.  In the design phase, of the Roaster, the limitations of the bean and the requirements to start the chemical reaction, referred to as roasting, determine the roasting precepts.  We do not believe in using extreme 400°C plus air  temperature that mostly moves around the batch of beans.  The beans will burn on the outside before it is hot inside.  Agreed the beans are in motion and only subjected to intermittent burning temperatures.  The average may be arithmetically acceptable but then so is keeping half your body in ice while the other half is in boiling water.  Perhaps some manufacturers slavishly follow this century old trend because it is easy and obvious.   


The starting point of the exothermic reaction ( above 180°C according to R.Eggers and at 200°C according to Clarke & Macrae).  We commonly use an air temperature of 240°C delivered under pressure so that the air is forced through the batch without initially losing more than a few tens of degrees.  The heat transfer to the beans, is slightly higher at the beginning of the roast when the beans are denser and able to transmit more heat internally.  Initially the heat absorbed serves to evaporate the moisture which determines the heat slope (how quickly the beans increase in temperature).  The decrease in bean density reduces the heat absorption by the beans hence the air temperature is rather uniform for the first and last layers.  Actually when the exothermic reaction begins the heat generated in the first layers raises the temperature of the beans that are down stream.   Delivering the air with sufficient pressure at 240°C is a challenge that will be addressed in a later post.  Sufficient to say that no off the shelf hot air blowers were found, resulting in another product development.


The Blower's pressurized air heats the beans and mixes them with a "bubble action" which helps reduce the contact of beans and the hot metal sides of the Roasting Chamber.  Some home roasters tout the advantage of their fountain mixing of the beans which is not optimal for roasting.  A fountain is created when the air flow is concentrated in one area which means that the air is not flowing through the rest of the beans i.e. not heating them evenly.


Time for a freshly roasted coffee.  Agree?

Food Processing vs. Nutrition ?

AKA - Does Processing make it a Lesser Food ?

The distilled opinion is "the more you process the less the consumer receives".

For various reasons the most common vehicle for food delivery has been perverted.  In response to "manufactured food", fresh food advocates are informing the public about  real food and real food costs.  

Living on the 100-Mile Diet , Revisiting Carrying Capacity:, Natural Foods, Organic Foods, etc.  It appears that greater "inputs" yield less nutrition.  Large marketing budgets promote convenience and "filling the belly" instead of feeding the body for growth and health.  Increased time spent transporting food means, as well, increased food degradation time.  Industry will typically attempt to address product appearance indicators that influence a consumer.  Unfortunately nutrition is sacrificed for the sake of colour and appearance.  

Before focusing on one product not usually covered in the fresh food debates I would like to add that I believe that the movement advocating quality food is gaining membership.  

My interest is the freshness of coffee.  Of course people do not live by freshness of coffee alone.  That would be silly because it mostly feeds the soul, the well being, the disposition, etc. Coffee has undergone a centralizing process which exchanged convenience for quality.  Bigger is not better if the product is lessened.  We have not developed Star Trek transporters to move food instantly to the consumer while maintaining the product integrity.  If the past is any indicator this futuristic device would further degrade the food.  Warehousing roasted coffee decreases the value to the end user.

I advocate that the coffee roaster, grinder, espresso machine, and brewer should be at the same site.  Nothing gives more credibility to the freshness of the product as when the consumer can observe the preparation.  To this end Jim Townley uses the moniker of "the Theatre of Roasting".  It encourages clients to learn about the process while it reinforces the artisanal qualities of freshness and caring preparation.  Small batch roasting, in our case 3 kg batches, allows the RoastMaster to roast the requirements of the next few days.  Most likely more than one batch of each coffee will be roasted but that is a choice based on sales.

This is a simple food preparation model even though it appears to counter the produced locally mantra of some of the above links.  We are not blessed with local coffee plantations but because the coffee bean is a seed which is designed by nature for long term storage it may be consumed at a distance from its origins with a certain proviso.  So where is the Freshness Challenge?  Roasting transforms the bean and creates havoc with the storage capability of the bean.  Roasted Coffee degrades quickly despite touted storage "solutions".   Freshly ground stale beans is an advertising distraction which offers no benefit to the consumer.  The analogy of the weak chain link is true.  Nothing will resurrect stale coffee not even a marketing campaign.  

For the best cup of coffee start with a freshly roasted high mountain grown Arabica bean that is ground just before brewing.

Staling of Roasted Coffee

Coffee stales much faster than it is commonly perceived.  An extreme example is noted in "Coffee Technology"by Michael Sivetz where he mentions that moisture absorption from the air or due to water quenching need only to be 1% to noticeably stale coffee within the hour.  This represents 30 cc (1 fluid ounce ) per 3 kg ( 6.6 lb ) batch which,  considering that the beans lost 12 to 20 times that much moisture when roasting, is quite significant.  Advocates of water quenching claim that all the water evaporates as it hits the bean.  I am not so certain that this is so because after roasting the bean is very porous which means that the water will quickly cool the outside layer the bean will then have difficulty conducting the heat to the surface to evaporate 100% of the moisture.  The increased porosity will help draw the moisture inside.

Each opening of the container allows more moist air to reach the roasted coffee.   Sivetz writes that the beans are "moderately stale" within a week, more stale within two weeks and stale in three weeks.  Greater surface area i.e. ground beans significantly increases the absorption of air and moisture.

Vacuum packaging does remove most of the air but if it is done within a few hours of roasting it can create problems because of the high pressure CO2 will be released from the beans and inflate the bag.  If the coffee is ground the CO2 will be mostly released within the hour.

In theory the Valve on the Bag permits a longer storage time but I am sceptical about that valve working perfectly.  The changes in air pressure are small and applied over long periods of time as the barometric pressure changes which causes the bag to breathe.  The valves are attached to a bag that is filled with coffee beans which is not a flat surface hence I am thinking that it leaks and that it's purpose is to prevent the bag from bursting from C02 pressure.  Before going further that has to be tested.  I reiterate that the only safe bet is buy Freshly Roasted coffee.

No Carbon Credits Required !

November 1st, 2011 – Victoria, B.C.

Many coffee roasting companies across Canada claim 'carbon neutral' status these days, however, consumers are encouraged to look closely at their labels to find out 'how' they achieve this. Carbon credits are being bought by a number of roasting companies whose technology is outdated and continues to pollute the environment. Many companies are folding the costs of carbon credits into their cost of goods. 'If you look closely, many coffee companies are claiming carbon neutral status, but all they're doing is buying credits to offset their emissions', states Fresh Cup President, Jim Townley. 'The truth is, the consumer is likely paying a higher price for a product without even knowing it'. No matter how you slice buying carbon credits, they are a cost to any company and many companies are buying them more for their marketing value than the purpose that they were intended for. 'Whether you plant a tree, or buy credits to off-set the carbon emissions produced in making a product, it costs money', notes Townley. That cost has to show up somewhere along the line, and if the cost to buy credits is left low like it currently is, many companies will continue to pollute and make consumers pay the price. 'What's the point of low cost credits, if the cost can be added to the product for the consumer to pay ? Where's the motivation for companies to change their business practices to minimize the impact on the environment', asks Townley. 'Our approach is simple…be sustainable in how we roast coffee by reusing the heat, while drastically minimizing the emissions, then there's no carbon credits required'.

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There is even more to the story !

The unfortunate part about marketing claims vs. true development and technical improvements is that the marketing claims focus on changing perception rather improving the equipment.  It is the easy way out which in this case does nothing for the local air quality if someone planted trees hundreds of kilometres away.  The article above does not mention that it took a decade to reduce the Roastaire™ emissions to a small fraction of conventional roasters.  In the process the energy required to roast was reduced to about 1/6 of a conventional coffee roaster.

The Roastaire™ was designed for the Café environment where people can observe the roasting process.  We refer to that as the "theatre of roasting".  The roaster is a compact unit that includes Chaff Cyclone, SmokEater™ (pollution controls), Pneumatic Bean Conveyor, and a Packaging Silo.  The roaster is approximately 6.5 feet high.  The roaster is controlled by a computer based Roast Monitor which  also configures the roaster, through the use of pneumatic valves, for the various modes in the roasting process.

More information is given in the post "Sustainable Design Follows Function"  such as the attention given to ergonomics.  An obvious example is the placement of the Loading Hopper which is placed at counter height rather than above the RoastMasters head.  The roasted beans are quickly cooled internally so that the smoke can be neutralized before it is vented.  The aim has been to improve and streamline the roasting session.

Café owners that buy roasted beans see " FRESH Coffee! " post are simply paying for someone else's roaster without getting all the benefits.

FRESHLY Roasted Coffee!

FRESHNESS is a contentious topic.  Groups that can't provide fresh coffee because of their long supply chain attempt to ignore this essential factor when selling a perishable food.  Cafés that Roast OnSite say that coffee staling begins to be noticeable one week after roasting.  They aim to sell "take home coffee beans" within the week and to serve all coffee within 1 1/2 weeks.  The question they ask is "Would you buy 10 day old bread?".  We attempt to bolster this strategy by providing an efficient small batch 3 kg roaster which makes it easy for the café to roast only the coffee beans that are required for the next few days.  This roaster benefits from the advantages of using electric heating which allows the re-circulation of the heated air after it is scrubbed of the smoke particles.  The built-in SmokEater™breaks down the exhaust gasses which otherwise cause neighbours to complain about roasting odours.

Café owners that buy from a local roaster sometimes do have fresh coffee but, obviously, they can't proudly serve their own creation.  The passion of creation communicates very well at the counter.  Perhaps they do not really know when the coffee beans were roasted.  One RoastMaster explained it like this: we put it for sale as an estate arabica, after some time we make blends, and if we still have some left we wet a cloth with some flavouring and tumble it and the beans in a small drum.  Is that flavouring to enhance or mask?  To the Café owner "Does the cost of your coffee pay for your roaster or your supplier's?"

A lot of lobbying dollars were spent to convince governments that coffee beans last more than 18 months therefore did not require expiry dates, in other words they concluded that roasted beans were non perishable.  This decision was required by centralized roasters and grocery chains because they cannot transport the beans to client coffee pots within two weeks.  Consequently, they promote peripheral messages such as freshly ground, freshly brewed, consistency, convenience, low price, contests, etc.   They can accessorize the product as much as they want but if you start with stale beans you can't make a quality drink.  Coffee parallels the preparation of food in that increased processing equals diminished quality.  Some of the tricks are to add cheaper robusta beans, which are more bitter than arabica beans, to the blend so that the espresso will have more crema like freshly roasted coffee.  It is not a great espresso and most likely they will suggest that you give it some zing with a flavouring.  Freshly roasted coffee has plenty of zing plus it has complexity that a flavouring does not even try to achieve.

Out of curiosity two books were consulted; one by a large Italian central roaster and other by UK specialists.  The first only mentions "freshness" as it pertains to serving it quickly after it is brewed.  The second book does not mention freshness.  Freshness is not part of the centralized roasting business model.  As a consumer the choice is yours "Do you wish to pay for freshness or warehousing?".

Packaging is often ascribed miracle properties.  In the first day(s) following roasting the beans emit a lot of carbon dioxide which can burst bags.  Hence, the use of the valve.  If the valve is the highest point in the bag the CO2 will force out the lighter gases such as air which is beneficial but it is hardly locking the flavour in.  One web site says that packaged coffee lasts a few months until the bag is opened but a little further down they claim: How long does coffee last? Coffee packaged with a freshness valve = 12 months then add a little further Ground coffee once the bag is opened = 2 weeks.  Check for consistency of message and verify that information.  Your priority is taste or the coffee experience theirs is sales.  Studies have been done about slowing down the degradation through cold storage but that requires colder deep freezers than those in homes.  An additional problem is that, due to the pressure differential, the deep freeze is the area with the highest humidity in a house.  Moisture accelerates staleness.

If possible observe a roasting session, you will learn.  You may find that some of the urban based coffee roasters are not used because of pollution complaints and that some RoastMasters , that do not have Afterburners, roast during the night. 

To improve the roasted beans' relatively short lifespan they should be ground just before brewing.  Make a comparison with beans that have been ground for half an hour. I expect that after half an hour the finely ground beans will make a flat coffee.  An espresso will have greatly reduced crema.  You will then be in a position to judge the statement "Ground coffee once the bag is opened = 2 weeks"

My mantra is "Buy from the roaster".

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.