Why is recirculation essential in coffee roasters?

Esther Gibbs
November 9, 2022
Why is recirculation essential in coffee roasters?

As with many other industries, sustainability is a growing concern within the specialty coffee sector.

The effects of climate change are having devastating effects on coffee cultivation, creating heated debates around coffee pricing. More recently, the startling increase in energy costs around the world is threatening the future of several businesses.

Many roasters make a point of sourcing their coffees ethically and ensuring the farmers are fairly compensated. Additionally, they have shifted away from traditional plastic packaging and adopted sustainable alternatives. 

That said, what else can roasters take into consideration when reducing the environmental impact of their business? 

The majority of coffee roasters use gas to power their roasters. While there is a delightful aroma released from the machine while it is in use, there are also emissions of volatile organic compounds (VOCs) which pollute the local area and add to a company’s carbon footprint. 

As a result, many have begun practising recirculation or partial recirculation in order to reuse the hot air released by the roaster. 

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An image of a coffee roaster roasting coffee beans in an article about why recirculation in coffee roasting is important

What are recirculation systems in coffee roasting?

During a roast, VOCs and particulate matter, such as carbon monoxide and carbon dioxide, exit the roaster through a chimney or flute.

To prevent this, many roasters use an afterburner, which can purify the air by heating it up to an extremely high temperature. This reduces pollution and enables roasters to comply with local pollution legislation.

That said, many afterburners require gas to fuel themselves.

As a result, many brands of roasters have begun using recirculation or partial-recirculation as an alternative. This practice uses the hot air released from the roasting drum and pushes it back through the roaster.

In essence, recirculation works by taking the exhaust air from the drum of the roast and returning it through the drum of the coffee. 

Notably, the air being exhausted is a pollutant. If this air were to go directly back through the roaster, it may give the coffee a smokey and tainted flavour. 

Therefore, it must go through some sort of filtration process before being recirculated back into the roaster.

Some of the benefits of recirculation include the reduction of carbon emissions and energy consumption, as the air is not being heated from an ambient temperature throughout the roast.

An image of a barista pouring filtered coffee into a glass coffee jug in an article about why recirculation in coffee roasting is important

What are the benefits of recirculation systems?

A number of highly successful roasters use recirculation, such as Loring, Probat, and IMF.

Loring uses a closed system for roasting, that features their patented Flavor-Lock Roast Process. 

Their closed-system removes the requirement for an afterburner and the technology can guarantee a cleaner and brighter coffee with a clean cup every time.

More so, the low-oxygen environment preserves coffee flavours and reduces CO2 emissions while reducing fuel costs by up to 80%. 

By recirculating air through their purifying system, Loring is able to ensure the air in the roaster can reach the target temperature with less energy.

UK-based coffee roaster Monmouth Coffee recently made the switch to a Loring and stated its findings on its website.

The website states that the company were worried there would be a smoky after-taste to the coffee or some kind of hot air taint. “There was nothing of the sort,” the review reveals.

“The recirculation was much cleaner than we anticipated, and the efficient heat transfer really let the coffee show us what it was all about – the high notes were crisp and the natural body and sweetness of the coffees came through,” the website explains. 

Monmouth Coffee has also commented on how much more energy efficient the roaster was.

On the other hand, Probat uses a partial recirculation. This means it is not a fully closed system, where the clean air is passed through the afterburner and released into the atmosphere. 

Probat realised the valuable heat and energy lost during this process. Therefore, the company uses part of this cleaned, heated air to feed directly into the roasting process.

In addition to reducing emissions, the air must pass through the afterburner anyway, reducing the use of fossil fuels by about 30%.  

Probat has also integrated a low-temperature catalyser, which has its own heaters, helping increase energy saving to 40%.

IMF roasters use two systems for their recirculation: the Vortex system and the Equaliser system. 

The Vortex system mixes ambient air with the hot, recirculated airstream before it enters the roasters via a modulator. This ensures it is at the correct temperature. 

The Equaliser system uses the same volume of hot air inside and surrounding the drum surface to enter the roaster, creating an even distribution across the surface of the coffee beans. 

This results in equal heat transfer, consistency and precision. This technology is now available on shop roasters as well as on an industrial scale. Through their systems, roasters may be able to save between 30% and 47% of gas consumption and reduce carbon emissions.

An image of a coffee roaster evaluating between batch protocol during a coffee roast in an article about why recirculation in coffee roasting is important

Why should roasters consider using recirculation systems?

There are a number of ways roasters can build their business to reuse energy and reduce emissions. These machines are more efficient as they essentially recycle hot air.

Having the air at a hotter temperature when it reenters the roast can save on energy, and keep the roaster at a consistent temperature, meaning it will distribute heat more efficiently. 

In turn, more energy can be transferred via conduction and convection, offering a more even roast. This can be particularly useful for high-density beans with high moisture content, as the heat will penetrate the bean with more energy. 

With this in mind, roasters will need even less heat source to roast a low moisture or low-density bean due to the stability of the temperature of the roaster.

The recirculation will also help with a more consistent in-between batch protocol, as the recycled air will not need much cleaning. Additionally, the roaster will not be constantly heating up the air from ambient temperature while the finished roast is in the cooling tray. 

A roaster with recirculation technology has the potential to save on fuel costs from between 25& and 80%.

It can reduce carbon emissions by up to 70%, and as long as the filter of the purifying system is cleaned regularly, it does not appear to have any negative impact on the final cup.

An image of a coffee roaster packaging fresh roast coffee into a kraft paper coffee bag with a transparent window in an article about why recirculation in coffee roasting is important

Investing in biodegradable, compostable, or recyclable coffee packaging and takeaway cups is another highly effective way to reduce the carbon footprint of your business.

At MTPak Coffee, we offer a range of 100% recyclable coffee packaging options made from renewable materials such as kraft paper, rice paper, or multilayer LDPE packaging with an environmentally friendly PLA lining, all of which minimise waste and contribute to a circular economy.

More so, we give our roasters complete control over the design process by allowing them to build their own coffee bags.

Our design team is available to help you create the ideal coffee packaging. Plus, we are able to custom-print coffee bags using innovative digital printing technology, with a quick turnaround time of 40-hours and 24-hour shipping time.

MTPak Coffee also offers low minimum order quantities (MOQs) to micro-roasters who are looking to remain agile while showcasing brand identity and a commitment to the environment.

For more information on sustainable, custom-printed coffee packaging, contact our team.

Esther Gibbs
Esther Gibbs

Esther has been in the specialty coffee industry for 14 years working as a Q Grader, SCA Trainer and ESTA trainer. She’s also offers her services as a coffee consultant through Hope Espresso. Her passion for writing comes from her love of sharing stories about the industry and ensuring knowledge is accessible to all.

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