Hackster Restraint to Reinvention Spotlight: Fermentation Monitoring

For a time, the name “Java” was synonymous with coffee itself. While global coffee production has since diversified, Java coffee still commands special cachet and even has a programming language named after it.

90 percent of Indonesia’s coffee is produced by smallholder farmers without access to specialized post-harvest equipment. After harvesting, the coffee cherries are submerged in water to separate the unripe fruits by density. The ripe cherries are depulped to remove the skin and fermented in water to remove the mucilage before drying, hulling, and storage.

The fermentation stage is responsible for the characteristic taste of washed coffee. It is a delicate process that has to be closely monitored to prevent spoilage and unwanted sour flavors. Traditionally, it is carried out on gut feel and intuition, making the process hard to standardize and the final product inconsistent.

Malang is a major city in East Java, Indonesia, famous for its comfortable climate and beautiful landscapes. Both arabica and robusta coffee varieties are grown in the southern and eastern highland areas. However, the quality consistency problem affects most of Malang’s substantial coffee output, reducing its marketability and price.

Hackster’s Restraint to Reinvention innovation challenge, in partnership with Nordic Semiconductor, showcases simple, sustainable solutions to social issues in underserved regions.

Ahmad Radhy is a hardware engineer and a big fan of specialty arabica coffee. He is one of the contenders in the innovation challenge and has decided to merge two of his interests in a project that leverages IoT for improved coffee quality and consistency.

Coffee processing involves several variables, and a proper data collection and reporting system is needed to improve coffee quality consistency. Radhy's solution is a fermentation monitoring system built on Nordic's ultra-low-power nRF54L15 SoC. It features the ESP32 microcontroller, a DFRobot pH sensor, and the DHT22 combined temperature and humidity sensor.

The pH sensor is submerged in the fermentation vat to track the acidity of the solution, and the DHT22 sensor monitors temperature and humidity. Both sensors are interfaced with the ESP32 microcontroller, which processes and transmits the data to the nRF54L15 DK for logging, display, or transmission to a cloud server or mobile phone.

Temperature, humidity, and pH levels are the most important variables in coffee fermentation. Temperature and humidity directly influence the rate of fermentation and final coffee quality. Fermentation is usually complete at pH levels between 3.5 and 4.0. Tracking the pH of the coffee beans during fermentation also opens the door for possibilities, such as enhancing the growth of specific microbes to contribute certain flavor notes.

The drying stage is another critical part of the post-harvest process that affects the coffee beans’ quality, flavor profile, and shelf life. The coffee beans are either sun-dried or heated in drying chambers.

Mechanical drying is faster and easier to control, but it is not feasible for most smallholder farmers in Malang. Sun-drying is labour-intensive, highly dependent on weather conditions, and requires close monitoring of moisture levels and temperature. The vagaries of weather and fluctuations in temperature and humidity can affect the water content of the coffee beans and cause significant post-harvest losses.

Radhy's monitoring system will collect temperature, humidity, and light intensity data within the coffee drying house. This will ensure even drying without the added cost of a mechanical dryer. The information from the monitoring system will be accessible via a mobile dashboard with a user-friendly interface.

Radhy says his system will help the coffee farmers evolve from taste-based to data-driven coffee processing. It targets “both local and systemic drivers of post-harvest inefficiencies, positioning smallholder farmers to better adapt to a changing climate.”

Radhy is affiliated with the Instrumentation Department of the Sepuluh Nopember Institute of Technology in Surabaya, East Java. With his team, he plans to implement the fermentation monitoring system for 100 smallholder coffee farmers in Malang as part of a pilot project.

He expects adoption to be slow and gradual, given the technical skill and amount of behavioral change required of the farmers. Most farmers are risk-averse and will only be ready to adopt when they have solid proof that the system works.

The purchase price could also be an obstacle to adoption. Simple farm inputs and equipment are already a difficult purchase for many smallholder coffee farmers in Indonesia. “Sometimes it’s hard to buy sacks and drying tarpaulins, let alone buying sensors,” said a coffee farmer in Bajawa, a town of Flores, Indonesia.

Consistent coffee quality will enable the farmers to gain access to specialty coffee markets and charge a premium for their produce. If the farmers are assured that the tools will increase the selling price and reduce the risk of fermentation failure, they will be interested. Radhy mentions that a “rental or subsidy system can also open access.”

While coffee is the second-most-consumed beverage after water, the sector is quite delicate and vulnerable to climate change. Fermentation monitoring will reduce post-harvest losses, increase farming revenue, and contribute to a climate-resilient coffee economy.

Radhy's fermentation monitoring system is still a work-in-progress, but he discusses it in detail on the project page.