Early morning view from the mountain during coffee harvest
Early morning view from the mountain during coffee harvest

Kyle Freedman Researches How Low Cost Solar Drying Technologies in Honduras can Improve Coffee Quality through the Dry Chain

  • by jmwallach

Coffee remains one of the top 5 agricultural commodities globally and is the second most consumed beverage after water. With the recent advent of specialty coffee based on unique sensory attributes such aroma and flavor, there is an increased focus on improving coffee quality. One of the key contributing factors to quality degradation is poor drying and maintenance of dried coffee throughout the supply chain. Coffee production takes place in the humid tropics in many countries where the control of postharvest processing is variable due to lack of infrastructure
and knowledge of proper practices. With the support of the Henry A. Jastro Research Fellowship, I had the privilege of addressing this issue and improving postharvest drying practices of coffee in El Paraíso, Honduras in December 2019.

Figure 1: Experimental site in Honduras showing three of the solar dryers used (from left to right: UC Davis Chimney Solar Dryer, UC Davis Pallet Dryver, Raised Bed). Collaboration between UC Davis and Zamorano University.
Figure 1: Experimental site in Honduras showing three of the solar dryers used (from left to right: UC Davis Chimney Solar Dryer, UC Davis Pallet Dryver, Raised Bed). Collaboration between UC Davis and Zamorano University.

The objective of the research study was to evaluate the performance of four solar drying methods using natural process coffee. This was conducted at a high altitude, humid coffee growing region that represents much of Coffee arabica production globally and where coffee drying can be difficult to manage. The four dryers that were evaluated included patio, raised bed, UC Davis Chimney Solar Dryer, and UC Davis Pallet Dryer. Many drying practices that are conventionally used experience numerous challenges in controlling environmental factors that can degrade coffee quality such as temperature and relative humidity. By testing and identifying new technologies that can dry coffee quickly and uniformly in humid, tropical regions, producers can better preserve their coffee quality and the potential for increased prices of coffee can be realized.

Figure 2: Conventional washed coffee that sits in wet piles prior to transportation which significantly degrades quality
Figure 2: Conventional washed coffee that sits in wet piles prior to transportation which significantly degrades quality

Not only did my research project seek to evaluate low cost drying technologies for climates that are less desirable for drying, but also I was focusing specifically on using natural process coffee. This was due to the fact that they represent the highest moisture content since the whole cherry is used during drying, and thus more water has to be removed for drying. Natural process coffees are also not commonly produced in Honduras and serves as an avenue for product differentiation.  In addition, natural process coffees use less water and cost less to process, which can improve sustainability and support farmers during a time when coffee prices are volatile. 

While additional experiments are needed to test the performance of these dryers, it was clear that our experiments showed the need for additional drying technologies that increase drying temperatures, reduce relative humidity, and protect coffee from the environment. It was also evident that many growers lack knowledge of the drying procedures that can improve quality as incentives and the structure of local value chains does not reward quality. This is typically reserved for more advanced coffee farms that have international connections or participate in national competitions. More research is needed around ways to enhance local value chains, introduce new technologies, and most importantly provide education and extension that puts new ideas into the hands of producers. I am grateful to the Henry A. Jastro Research Award program for giving me the opportunity to learn how to conduct international field experiments and gain firsthand experience the challenges that coffee producers face.