**1. Introduction**

The importance of maize cannot be overlooked due to its significant role in fighting hunger and improving the socio-economic comfort of the people in sub-Saharan Africa [1]. In Ghana and many countries in sub-Saharan Africa, the crop is the most produced and consumed staple [2]. It is harvested at high moisture content, and as such, it is required that the moisture content be reduced to 12–14% to ensure safe storage for future use in humid and warm countries like Ghana [3,4].

Drying as a post-harvest activity is the most attractive method for conditioning food grains by removing moisture to a safe moisture level. This is because the drying process has proven reliable and flexible for removing moisture from food grains [5]. Although drying of food products is widely applied in various industries globally, it has been a challenge for the smallholder farmer in Ghana and other parts of sub-Saharan Africa.

In Ghana, drying of harvested maize is usually done using traditional drying methods where farmers leave the crop to dry in the field or the open sun next to farmers' homes or along roadsides, either on bare ground or on tarpaulins [2]. This reduces the quality of the dried maize grain and leads to contamination of dried food grains [6]. The situation becomes challenging when harvesting of food grains coincides with unfavorable drying weather conditions such as the rainy season, during which the drying process can take up to 5 days. Drying under such adverse conditions leads to the growth of molds [7], resulting in a considerable loss of food grains in terms of quality.

**Citation:** Obeng-Akrofi, G.; Akowuah, J.O.; Maier, D.E.; Addo, A. Techno-Economic Analysis of a Crossflow Column Dryer for Maize Drying in Ghana. *Agriculture* **2021**, *11*, 568. https://doi.org/10.3390/ agriculture11060568

Academic Editor: Johannes Sauer

Received: 15 May 2021 Accepted: 18 June 2021 Published: 21 June 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

In attempts to improve the process of crop drying by reducing the drying period, lower drying cost, reliability and accessibility of drying systems, and environmental issues associated with drying, there has been the introduction of varieties of drying system such as solar dryers [8,9], biomass assisted hybrid dryers [10], and other mechanical drying systems. However, most farmers have not widely adopted these interventions, and they continue to dry their harvested produce using the unreliable and inefficient open sun drying method [4]. According to Kaaya and Kyamuhangire [11], such drying technologies are capital intensive to install and operate, making their operation expensive for the smallholder farmer to patronize.

According to Chua and Chou [12], low-cost drying systems are more suitable for smallholder farmers in developing countries. They highlighted that such drying technologies should have low initial capital cost, easy to operate with no complicated electronic and/mechanical protocol, effective in promoting better drying kinetics. The authors also reported that low-cost drying systems should also be easily constructed with available local materials and be run on renewable energy.

The economic and technical appraisal of such drying technologies is vital for their adoption by smallholder farmers. Successful assessment of these low-cost technologies drives their scale-up from research laboratories to commercialization and adoption. This study sought to assess the economic and technical performance of a portable locally fabricated half-tonne capacity column drying system with a biomass burner for maize drying in Ghana.
