Bühler stands at the forefront of automation in coffee processing, building entirely automated production lines with auto-corrective profile control to guarantee roast consistency.
When Bühler launched the InfinityRoast in 2014, it had three objectives for the industrial coffee roaster: to be the most flexible machine in its class on the market, to have operational excellence in terms of energy use and maintenance, and maximum quality consistency of the coffee it produces.
To achieve this last goal, Dr. Stefan Schenker, Head of Business Unit Coffee at Bühler, says the Swiss manufacturer had to completely rethink the process control methods that coffee roasters had used up until that point.
“Most roasting systems simply have a burner directly attached to the roasting drum where all you can really influence is the temperature of the hot air that enters the chamber. You can roast in different steps and form a profile, but it’s really just different levels of hot air temperature at different times,” Schenker says.
“The coffee roasting process is affected by many external factors, like weather and humidity, whether the machine is just starting up or has been running all day, and the moisture content of the raw material as you move from one green coffee to the next. If you just control your inlet hot air temperature, the product temperature is not stable. This product temperature [of the beans] is what is actually important for flavour generation and how it evolves during the roasting process.”
With this in mind, Bühler focused the InfinityRoast’s profile control on the temperature of the beans themselves rather than the surrounding air. A well-placed and sensitive temperature probe accurately measures the bean surface temperature and allows the machine to adjust the roast process accordingly.
Schenker calls this auto-corrective profile control a highlight of the InfinityRoast.
“Once a profile or ‘master curve’ has been set, the auto-corrective system makes sure we follow the pre-defined and timed product temperature curve very precisely,” Schenker says.
“Whatever happens or whichever factors are at play, the system makes sure we stay on the master curve with the precision of plus/minus one centigrade. This way, the beans always follow the correct temperature evolution and stop the roasting process at the right time.”
While Schenker says many other modern roasters now measure the bean temperature, they’re not able to use this information to regulate the process. Instead, an experienced roast master must manually check the beans mid-roast to determine if adjustments should be made.
“You need a special roasting system for the InfinityRoast’s style of auto-corrective profile control, and there are hardware and software elements involved,” Schenker says.
“On the hardware side, you need a very responsive system. We have a fast-reacting gas burner which only takes a few seconds to adjust the energy input into the roasting chamber. On top of that, there is a small bypass into the roasting chamber where we can perform fine adjustments of how much air and energy enter the roasting chamber. With these two independent control loops, we can achieve this precision.”
The Infinity Profile Control software system monitors and controls all of these functions, as well as daily operations and enabling profile creation. Schenker says the level of control InfinityRoast has over the process provides it with a great degree of flexibility when it comes to these roast profiles.
“Imagine a chart depicting all the coffee roasters in the world, with roasting times on one axis and air-to-bean ratio on the other. In one corner, you’d find drum roasters designed for longer roasting times and a low air-to-bean ratio, and in the opposite corner, fluidised bed roasters using a lot of air to keep beans in motion for short roasting times. InfinityRoast can cover this full spectrum of operating conditions,” he says.
“We have conducted many trials with our customers where they ask us to do flavour matching. They want to update their roaster, but have an existing product on the market and say ‘can you match that flavour?’ Time and time again, we’ve shown we can.”
The InfinityRoast’s “operational excellence” was put to the test when Norwegian roaster Joh Johannson approached Bühler with the task of developing the “world’s most efficient climate- and environmental-friendly coffee processing plant”.
To make this possible, Bühler installed two InfinityRoast2000 units in the site, equipped with green bean preheaters that Schenker says can reduce energy usage by up to 25 per cent alone. Heat exchangers capture some of the energy released during the process to be stored and redistributed. A Regenerative Thermal Oxidation emission control system allows smart control of the air currents, which in turn enables more heat to be stored and returned to the process. These in total reduce the plant’s energy usage by 50 per cent, with the rest largely compensated with extensive solar panelling.
“For [Joh Johannson], sustainability is not only something they write about in their annual report. For them, it’s a business model. They see it as a competitive advantage in the market,” Schenker says.
While the Norwegian site is a leader in the field of sustainability, Schenker says a current project of Bühler’s for a large coffee capsule producer in the United States represents the next step in automation.
“It is a greenfield site, where Bühler is installing the complete processing technology from green bean intake, storage and blending, roasting, and grinding, up to the interface with packaging. For this customer, we are making the entire plant automated,” he says.
“This customer came to Bühler and said, ‘I want to have a fully automated coffee factory’. They gave us access to their [enterprise resource planning] (ERP) system, where they create their production schedules, and we took care of the rest.”
The site features two InfinityRoast-3000 systems and two smaller relocated existing roasters, eight grinders, and several packaging lines, with an annual capacity of 50,000 tonnes of roasted coffee per year. From start to end, the processing line is fitted with automated equipment and an interface connected to the ERP system.
Schenker says the plant can run with an absolute minimum of staff, with it feasible for one person in the control room to operate the entire processing line.
“From an automation point of view, you press the startup button and it works from there,” he says. “It’s the highest degree of automation I’ve seen in my 20 years in the coffee industry.”
Automation is a growing trend in many industries, and with it providing better quality control while taking pressure off onsite staff, Schenker says coffee will be the same.
“Our customers want to have better control over quality consistency. Fully automated plants give this and an operational benefit. Each unit of a line is aligned with the others, so you have automatic optimisation of the entire process,” he says.
“For this reason, it’s also in the strategy of Bühler to be at the forefront of digitalisation. We are already looking into next generation systems.”
Bühler has partnered with Microsoft to investigate how its customers – in coffee and other food industries – could benefit from big data and, in a way, learn from each other.
“We will be able to make sure our customers benefit from best practices all around the world,” Schenker says.
“That’s a big mission for the automation of the future – to connect your factory to a Bühler cloud solution, and in turn, receive plant optimisation so you can run your factory more efficiently.”
For more information, visit automation.buhlergroup.com/industries/coffee
This article appears in the November/December 2020 edition of Global Coffee Report. Subscribe HERE.