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Afterburners and Alternatives: Part 1

Coffee roasting

Smoke and odor arise naturally as a result of the coffee roasting process, leading to pesky problems. For roasters, finding the right solution requires careful analysis as each option has a unique advantages and drawbacks.

At Inproheat, we develop Smoke Dog afterburners (or thermal oxidizers) to reduce smoke and odor for roasters in the coffee and food industries. An efficient afterburner reduces and even eliminates smoke and odor, but what other options are available and how do they compare to afterburners?

In this post, we’re going to outline the pros and cons of air filtration systems, which are known alternatives to afterburners.

As food roasting often involves coffee, nuts, or fish, let’s break up the two main components involved in the roasting process.

First of all, roasting produces smoke. This is often dark black or light grey in colour and contains suspended particles, unburnt hydrocarbons, greenhouse gases and VOCs.

Secondly, roasting produces odor – which has no visible spectrum.

Interestingly enough, the critical difference between these two roasting components relates to our own human senses. Smoke concentrations have to be somewhere in the parts per millions to be detected by the human eye. By comparison, odor is much less concentrated – somewhere in the parts per billions – and still be detectable.

By using air filtration methods, roasters reduce smoke and odor to varying degrees, depending on exactly which system they are using.

Here’s a look at the benefits and drawbacks of several air filtration systems.

Filter Scrubbers

The Pros:

  • Cost-wise, filter scrubbers are an inexpensive upfront investment.
  • On the set-up front, they install easily.
  • Filter scrubbers benefit very small roasting operations.
  • Where the environment is concerned, there is no direct greenhouse gas generation.

The Cons:

  • Disappointingly, filter scrubbers have short lifespans and need replacement when an element is full.
  • In addition, backpressure from filters negatively affect the roasting process.
  • As well, the roasting odor is not fully eliminated from using them.
  • Furthermore, discarded filters generate waste.
  • Also, filter scrubbers fail to eliminate roasting-related VOCs.
  • Lastly, they are not compliant pollution-control devices in areas with stringent emission laws like Los Angeles or Seattle.

Electrostatic Filters

The Pros:

  • Electrostatic filters use electricity, so they generate no direct greenhouse gases.
  • For maintenance, there are simple controls with basic venting and electrical components.
  • On smoke removal efficiency, they remove approximately 80% of smoke particles.
  • In terms of odor removal, they reduce some without removing it all.
  • Cost-wise, they carry a medium up-front cost.
  • For roasters surrounded by neighboring businesses, electrostatic filters offer great technology to keep them happy.
  • As for durability, these products possess a long lifespan.

The Cons:

  • First off, electrostatic filters require elemental cleaning ranging from daily to weekly.
  • Also worth noting, larger models with increased duty do not fully eliminate smoke.
  • Without proper motivation, backpressure from filters has a poor effect on the roasting process.
  • Additionally, they reduce without fully eliminating odor.
  • Unfortunately, they do not eliminate VOCs.
  • Finally, electrostatic filters do not comply with pollution control laws in environmentally-stringent markets like Los Angeles or Seattle.

Wet Scrubbers

The Pros:

  • For controls, they are simple to operate with a basic venting and electrical set-up.
  • Concerning cost, they boast a medium up-front and low operating cost.
  • In terms of environmental impact, wet scrubbers generate no direct greenhouse gases because they use electricity.
  • As a final benefit, micro level wet scrubbers are scalable.

The Cons:

  • Most notably, scrubbers create waste water during the roasting process. Waste water’s harmful contaminants require specific disposal procedures.
  • In addition, these products don’t fully eliminate smoke and odor.
  • Furthermore, they do not eliminate VOCs.
  • Unfortunately, in environmentally-strict markets, scrubbers do not comply to emission laws and regulations.

In conclusion, air filtration systems are best-suited to smaller roasting operations in markets with more relaxed emission bylaws. Because of their low cost and basic operation , they have their own appeal.

Ultimately, roasters need to weigh these benefits against drawbacks like regular cleaning, waste water creation, and the failure to completely eliminate smoke, odor, VOCs.

Our next blog post will examine the different variations of afterburners and their respective pros and cons.

Interested to know more about Smoke Dog afterburners by Inproheat? Get in touch! Contact us to discuss your roasting operation and discover our afterburner products.