## 4 Conclusions  
This study demonstrated that for processing cassava grids, the pneumatic dryer was more energy efficient than the fixed-bed dryer. However, the Whiteness Index of the flour produced by the fixed-bed dryer was higher, but the other colour parameters were not significantly different. In addition, the staff controlling product quality could not distinguish flours produced by each dryer. This led us to conclude that consumers would equally accept both products. Regarding costs, the pneumatic dryer had a higher capital cost but a lower operating cost, and to recover the additional investment made for this dryer, a short amount of time was needed. Therefore, this comparative study allows us to conclude that  
Figure 7: Sensitivity analysis showing the influence of (**a**) diesel price and (**b**) electricity price in the pneumatic dryer payback period. the pneumatic dryer is a better choice of equipment for cassava processing by small-size enterprises in Africa, and for this reason, we recommend that this should be the type of dryer promoted and disseminated by policymakers and researchers working on rural development. Conceptualization, M.P., A.C. and J.M. ; methodology, M.P. ; data collection, M.P. and G.A.K. ; laboratory analysis, G.A.K. ; data analysis, M.P. and A.C.; writing, M.P. ; artwork, M.P. ; supervision, J.M. ; project administration, M.P. ; funding acquisition, M.P. All authors have read and agreed to the published version of the manuscript. This research was funded by the CGIAR Research Program on Roots, Tubers and Bananas (RTB). Gratitude should be expressed to Tropical Starch Company Limited for taking part in the research. We would also like to thank [PERSON] for his helpful suggestions during the writing of this paper. The authors declare no conflict of interest and the funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. * [PERSON] _et al._ (2008) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Effects of operating practices on performance of a fixed-bed convection dryer and quality of dried longan. _Int. J. Food Sci. Technol._**2008**, _43_, 1979-1987. [CrossRef]
* [PERSON] _et al._ (2010) [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] Improved quality and energy performance of a fixed-bed longan dryer by thermodynamic modifications. _J. Food Eng._**2010**, _99_, 392-399. [CrossRef]
* [PERSON] _et al._ (2016) [PERSON]; [PERSON]; [PERSON] Increasing the Energy Efficiency of Batch-Type Drying with Partial Air Recirculation. _Chem. Ing. Tech._**2016**, _88_, 208-214. [CrossRef]
* [PERSON] (2014) [PERSON]; [PERSON] Safety aspects of industrial dryers. In _Handbook of Industrial Drying_, 4 th ed. ; [PERSON], [PERSON]; CRC Press: Boca Raton, FL, USA, 2014; pp. 1127-1151. [CrossRef]
* [PERSON] (2019) [PERSON] Performance, energy, and product quality aspects of a modified pneumatic dryer for rapid drying of high-moisture paddy. _Trans. ASABE_**2019**, _62_, 1531-1539. [CrossRef]
* [PERSON] _et al._ (2018) [PERSON]; [PERSON]; [PERSON] A comprehensive review on modeling of pneumatic and flash drying. _Dry. Technol._**2018**, _36_, 33-51. [CrossRef]
* [PERSON] (2020) [PERSON] Primary energy demand and energy costs of fixed-bed drying using the example of chamomile flowers. _Dry. Technol._**2020**, _38_, 434-447. [CrossRef]
* [PERSON] _et al._ (2019) [PERSON]; [PERSON]; [PERSON]; [PERSON] Drying efficiency and product quality of biomass drying: A review. _Dry. Technol._**2019**. [CrossRef]
* [PERSON] _et al._ (2012) [PERSON]; [PERSON]; [PERSON] Drying of High-Moisture Paddy Using a Combined Impinging Stream and Pneumatic Drying System. _Dry. Technol._**2012**, _30_, 1854-1862. [CrossRef]
* [PERSON] (2008) [PERSON]; [PERSON] [PERSON] Thermodynamic interactions in a fixed bed drying process using heat pumps--Fundamentals and implementation. _Z. Arzaei Gewurzpflanzen_**2008**, _13_, 167-172.