To afterburn or not, that is the question facing 'green' roasters 


Bend your brain on this: burning exhaust itself. As in, generating heat, say 600 to 800 degrees, that's hotter than the, say, 400-degree effluent from something else burned, which further breaks down particulate matter and smoke, leaving a clear, cleaner haze not unlike what radiates from sun-baked pavement.

OK, that wasn't so bad, right? Burning smoke — got it.

But why do some coffee roasters do it, and urge that everyone should, while others ignore or even vehemently oppose the practice?

The answer proves as elusive as a decision in the roasting world's greater, aesthetic debate: drum roasting (using a big, rotating metal cylinder) versus air roasting (à la glorified popcorn maker), which I'm not daring to delve into here.

What I am specifically examining is environmental consciousness in the roasting process. It's something trending nationally — and locally, with two roasters. Both want to be the greenest bean stewards possible, and yet they fall on far ends of the spectrum when it comes to practice and philosophy.

Glenn Powell, owner of the Springs' oldest continuous roaster, Barista Espresso, shelled out $52,000 shortly after opening to buy an afterburner — basically, a big metal silo, connected to exhaust pipes, that does what's described above. That was roughly 25 years ago, after he'd bounced out of an espresso machine design-and-rental business to start his own roast operation. It was a time when he counted only two espresso machines citywide, and recycling represented the apex of sustainability awareness.

"It was the right thing to do for us," Powell says simply.

Since then, Barista's become fair-trade and organic certified, and a staple at many local restaurants. Now, roasting on two 58-pound Primo drum units that feed chaff (the coffee cherry's skin, which burns off) into a collector and exhaust into his afterburner, he's never had to worry about neighboring business' concerns over odors (more "pungent" and "musty" than the pleasant aroma of roasted beans) and he believes he's reducing his most harmful greenhouse gas emissions.

According to Colorado Department of Public Health and Environment advisory documents, "gaseous emissions" from coffee roasting "include aldehydes (e.g., formaldehyde, acetaldehyde), organic acids, phenols, and other hydrocarbons ... [and] nitrogen oxides and carbon monoxide emissions occur as a result of the combustion of natural gas."

The regulating agency sets a limit of two tons annually of four main volatile organic compounds before an afterburner would be required — which answers why all of our other local roasters, who are assumed to not reach that threshold by virtue of their size, need not futz with one.

Agreeing that all roasters will unavoidably produce some emissions, CDPHE permit engineer Chuck Pray calls the breakdown of hydrocarbons into carbon compounds via afterburners a "lesser evil."

So, win for afterburners, yeah?

Not so fast, says Mission Coffee Roasters' Brett Bixler, who contacted CDPHE before relocating his family from Baltimore a couple of years ago, "to do what I could do to keep Colorado clean and safe."

He says, "At the craft, small-batch scale, I'm genuinely more concerned that an afterburner does more harm than good. Look at the extra use of utilities required ... you're using two to three times the natural gas to burn off particulates. It's a catch-22 or circular argument."

Over the course of a year, he worked with state engineers to calculate his projected emissions (a process he believes he's alone in), and found that his respective releases on the big four were only .09, .21, .20 and .02 tons on those allotted two tons annually.

"If my roaster ran all day long, seven days a week, I would never cross that threshold," he says, complimenting his 26-pound Diedrich drum unit for being super energy-efficient. (Powell's Primo is a Diedrich offshoot; both are regarded as great at holding heat, requiring less input gas during lengthy roasting.)

Bixler, who worked for Diedrich from '91 to '96, says that on a Starbucks and big-conglomerate scale, he can't imagine afterburners or air scrubbers of some sort not being necessary. But he's personally more concerned about the effects of cattle feedlots and diesel vehicles on air quality.

True — coffee emissions overall appear low on the totem pole, like wood-oven pizza cooking and the like. But short of afterburners, which start at $25,000 to fit a roaster like Bixler's, can we do better when burning our beans?

Roaster designers such as Lilla and Loring believe so, and have created units that recirculate heated air for higher efficiency in a closed-loop environment. Denver's Coda Coffee, which earned Roast Magazine's 2014 Macro Roaster of the Year award, says its Lilla halves its energy consumption.

Bixler's not convinced: "We want clean, fresh air to hit the coffee, [not] atmospheric combustion gases," which he believes affect flavor.

Instead, Bixler points to Pueblo's Solar Roast Coffee as the company with the right idea. It offers the "world's only commercial solar powered coffee roaster," actually a rooftop array of photovoltaics that power its 40-pound hybrid unit, which generally roasts at lower temperatures, too.

And so it goes. If we can't erase emissions altogether, or even agree on how to combat them, at least we can address creative inputs, while ever-striving toward that perfect cup.


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