Day 2 - Tropentag 2023, Tropentag2023

Hybrid tunnel solar dryer for coffee processing in Colombia

Eduardo Duque Dussán, PhD student at the Czech University of Life Sciences in Prague, presented his study on developing a new hybrid system to dry coffee beans.

Eduardo Duque Dussán

Colombia’s coffee production is the third highest in the world, with an average of 11.5 million bags a year. A critical step for producing a high-quality and safe product is the drying process, which traditionally consists of exposing the trays containing the coffee beans to the sun and letting it do the job. This method is sustainable and easily applied, but the weather conditions lead to challenges. Indeed, during the rainy season, due to the reduced sun hours, the drying can critically extend up to more than 14 days. This can negatively affect the quality of the products all the way to spoilage, leading to important products and therefore profit losses.

The goal of Eduardo’s research is to develop a hybrid solar drying unit as a response to this issue, which would decrease the drying time, function 24/7, regardless of the weather conditions, and finally increase profits. A very interesting point is also the alternative heat source that has been tested during the experiments. After the harvesting of the coffee beans, millions of tons of trunks are left on the field and have to be disposed of to prepare the field for the following crop. This hybrid solar drying unit is designed to use those trunks as heat sources, which would represent a great step towards a circular economy.

The results from Eduardo’s research show that this hybrid unit can indeed decrease the drying time up to 70.47% with constant mechanical aid, and 47.75% when only used during the night. This evidence is very promising, and the production of these units on a large scale units can represent a viable solution for sustainable but still more efficient coffee production not only in Colombia but in all producing countries.


Duque-Dussán, Eduardo and Sanz-Uribe, Juan and Banout, Jan, Design and Evaluation of a Hybrid Solar Dryer for Postharvest Processing of Parchment Coffee. Available at SSRN: or