How Roasters Stay Ahead of Air Quality Rules

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By Jenny Neill

A year ago the European Commission began legal proceedings against the United Kingdom for failing to meet 2010 pollution reduction targets. That same body has found itself under increasing public scrutiny after reports surfaced that it would no longer pursue ambitious air quality targets. 

The contents of “work plan proposals” leaked farther than European Union v.p. Frans Timmermans may have intended in December. Just four days after he shared (and collected back) paper copies of documents suggesting a number of waste and pollution related proposals be scrapped, the British daily newspaper The Guardian reported the story. A few days later, after many members of the European Parliament voiced discontent, the “flagship clean air directives” were back on the table. 

Of European air quality standards, Robert Austin, president and c.e.o. of Loring Smart Roast, Inc., said, “There are no uniform environmental standards – we wish there were.” 

Thomas Koziorowski, director of product technology in research and development at PROBAT-Werke von Gimborn Maschinenfabrik GmbH (Probat), shared a similar opinion. He said, “In recent years, discussions regarding climatic issues worldwide have turned emission regulations into a dynamic subject as they are constantly undergoing changes; emission limit values cannot simply be considered as being [a] given.” 

What will the European Union Commission’s clean air directives mean for coffee roasters or those who design and manufacture roasting equipment? 

“Europe seems at this time to be most concerned about smoke and smell, and less so about NOx, CO2 , CO, etc. – but this whole issue is moving very quickly all over the world – so if you ask us tomorrow – the landscape may have changed,” said Austin.

Boutique coffee roasters, especially those outside urban areas, tend not to concern themselves with how public health outcries or climate change worries drive rulemaking. With so much discussion happening at international and national levels, now is the time for roasters big and small to evaluate which greenhouse gas precursors they release and how much particulate matter escapes during the roasting process.

Matters of size and smell

Countries in the European Union share one commonality when it comes to setting emissions standards: the bigger the facility, the more likely an air quality rule will apply. Another similarity is that smaller roasters, those that roast 99 pounds or less per batch, tend to fall into a gray area where compliance may come down to keeping your neighbors happy more than anything else.

Klaus Thomsen, head barista trainer and p.r. manager for Collective Coffee in Copenhagen, Denmark, reported the company roasts about a ton a week at the Godthåbsvej roaster with a 35 kg Loring SmartRoast. Loring roasters roast the coffee and incinerate the smoke and odor with a single burner. 

Before investing in the SmartRoast, Collective Coffee used a 12 kg roaster with an electrostatic filter and eventually added “ceramic stones” to reduce emissions during the roast process.

 “If someone complains then the environmental department will come out and check the air for how many particles we’re letting out (I think). But it hasn’t happened for us,” Thomsen said.

Jos Cozijnsen, a consulting attorney on emissions trading, explains that industry deregulation can be problematic for microroasters in Europe. With no clear classifications for smaller scale equipment, local authorities have more leeway to determine air quality standards. One of Cozijnsen’s recent projects involved attempting to prove the odors emitted by a Loring SmartRoast machine, designed in California to meet the strict air quality requirements there, would not be a pollution problem. However, the test used in the region to which the roaster will be sent was designed for a facility that continuously releases exhaust.

European and American agencies indeed monitor air quality using different methods. According to Kevin Summ, director of marketing for Anguil Environmental Systems, compliance is measured using milligrams per cubic meter in the exhaust at the source in Europe. In the U.S., regulatory agencies instead check to verify that 95-99% of volatile organic compounds and hazardous air pollutants are destroyed. Those differences might not seem significant; but for coffee roasters it means different emission equipment designs depending on location. 

 “The test is not [a] fit yet,” said Cozijnsen. “We believe we can show that exceptions [should be] allowed. Bottom line: The Loring is too clean for the existing rules and test methods [there].”

Manufacturers in America have adapted to U.S. pollution abatement rules by trying to roast with a cleaner exhaust.

Idaho-based Diedrich Manufacturing is known for its infrared burners. Compared to equipment that uses an open flame, Diedrich roasters have a cleaner exhaust due to incorporation of heat exchangers in the machines’ designs. 

Infrared burners only produce 3-4% of the NOX gases, 40-60% the CO and CO2 exhaust, and average aldehyde emissions of 30% when compared to open flame roasters, according to the company. The various types of SOx and zene gasses average only 45% of that produced by gas burners.

Diedrich “has worked diligently, both internally and with other companies, seeking solutions while at the same time maintaining the very positive contribution we have demonstrated historically on the coffee we roast,” said c.e.o. Michael Paquin. 

He said that at this year’s Specialty Coffee Association of America gathering his company “working in collaboration with another firm” will unveil “a ground breaking and exciting demonstration of the direction we are headed in.” 

Burn Out

While many approaches may be used to reduce or eliminate pollutants from food processing exhaust, the most common approach with coffee is to apply more heat. Afterburners are typical for small roasters. Larger plants may employ catalytic or regenerative oxidizers instead. All three rely on some amount of heat in the oxidation process. These methods are preferred to some other technical innovations because roasting exhaust, to those who specialize in air pollution remediation, is “dirty.”

Scott Bayon, director of sales at Anguil, noted, “What’s in the exhaust from a coffee roaster is typically a strong odor, condensable organic oils and chaff. We know the particulates (chaff) and oils will be an issue in oxidizer selection.”

For many, the simple application of more heat to oxidize by incineration is falling out of favor because of high fuel costs. The other two oxidizer types, catalytic and regenerative, use less gas: catalytic because it operates at a lower temperature and regenerative because it captures and reuses heat before it escapes the system.

Anguil has been selling oxidizers since 1978 with approximately 1,800 units deployed worldwide. More than half of those are catalytic because many of the company’s early customers were bakeries. Bayon explained that this type of oxidizer tends to weigh less in addition to not needing as much heat to operate. Many commercial bakeries like both characteristics because the most logical location for installing pollution control equipment in these businesses is often on the roof.

Though property constraints may dictate oxidizer choices for bakery settings, coffee companies more often seek to reduce operating costs. Catalytic oxidizers operate at lower temperatures but rely on a consumable catalyst for oxidation to take place. Those consumables are precious metals that need to be replaced every 2-3 years.

“You could [spend] as much as $20,000 to $30,000 [replacing the catalyst] in these units,” Bayon said.

Some European roasting equipment suppliers have developed products and system designs that incorporate one or both approaches to reducing pollutants and greenhouse gas precursors from roast exhaust. 

According to Koziorowski, nearly all of Probat’s industrial roasting systems utilize a process that recirculates the smoke from roasting back to the burner and reheats it to roasting temperature. 

The Proforte uses a flameless, regenerative, thermal oxidation process to meet the lowest emission guidelines. “Here the roasting exhaust gases are led through a ceramic bed whose interior has temperatures of 900 to 1,100°C,” according to Probat.

Probat’s entire range of exhaust air cleaning technology, including the thermal pre-cleaners, is modular, explains Koziorowski — this facilitates cost-effective retrofitting of a catalytic afterburner, for example, to meet ever-changing emission rules.

He explained the benefit to a roaster operating in Germany: “When using a thermal pre-cleaner with catalytic afterburner, the [target] value for the total carbon content of the roasting exhaust air as per German air pollution control regulation - commonly referred to as ‘TA Luft’ - is [met].”

Bayon said that, “RTOs are the most popular oxidizer technology across almost all industrial applications due to the high internal heat recovery and associated reduction in gas consumption. The catalytic oxidizer is limited to a maximum internal heat recovery rate of about 65% — RTO will achieve 95%.”

When asked if there were innovations happening with RTOs, Bayon reported that some advances have been made with the materials, ceramic plates mostly, which act as heat sinks. These and other advances have the effect of upping what Koziorowski called the “thermal degree of efficiency” to above 95%. 

In the case of the Proforte from Probat, the thermal efficiency ranges from 95-98%. Most RTOs have a minimum of two chambers with ceramic beds. To function properly, the system needs to warm up. This requirement may make RTOs less desirable for companies that do not roast seven days per week. Preheating the oxidizer once a week erodes fuel efficiency savings. 

But for a large facility that does operate every day?

Bayon said, “That’s really the whole point of the RTO, to minimize fuel costs. If you look at a commercial roaster using just an incinerator, you could easily be talking about hundreds of dollars an hour in gas just to run those incinerators. Whereas an RTO might [cost] $10 per hour, it’s that drastic [a difference].”