Techno-economic assessment of a greenhouse solar coffee dryer: a case of Coffee arabica L. in Ethiopia

Abstract Coffee is the backbone of Ethiopia’s economy, supporting over 15 million smallholder farmers and accounting for about 30% of national export revenue. Advancing coffee processing, like adoption of solar dryers, has the potential to maintain sustainability and coffee quality, thereby increasing economic and social benefits. This study is aimed at experimentally assessing the techno-economic performance of a novel greenhouse solar coffee dryer (GHSD) under the weather conditions of Yirgacheffe, Ethiopia. In addition, this study introduced a new index (Flexibility Index) to assess the drying methods’ flexibility in controlling and adapting to varying weather conditions. Experiments were conducted under varying conditions to assess drying time, efficiency, quality, operational flexibility, economic, and environmental impacts. The results showed that the GHSD reduced drying time in average of 52. 4% for the dry and 35% for the wet process, with corresponding improvements in drying efficiency of 47% and 36%, respectively. The flexibility Indices were 62. 5% and 94% for TOS and GHSD methods, respectively. Furthermore, although both carefully dried coffees using TOS and GHSD methods achieved Grade1 with scores above 86. 5%, the coffee dried using GHSD scored up to 1. 7% higher in quality assessment. The economic and environmental assessment indicates that the GHSD’s PBP is estimated at 1. 44 years, while the EPBP is 2. 84 years with a carbon credit of 1493. 1 over 25 years. In addition, the GHSD requires 39% less drying area than TOS method. Therefore, according to this study's findings, GHSD technology is an efficient, quality-preserving and environmentally friendly alternative to coffee drying methods. Graphical Abstract