Technical performance and economic efficiency of small-scale maize dryers in Kenya

Maize is the most important cereal in East and Southern Africa, but its production is highly seasonal. Maize storage is therefore essential for food security, and so is drying before storage, typically to 13.5%. New small-scale dryers have been proposed but their performance has not been tested. The technical performance and economic efficiency of small maize dryers were therefore assessed during two on-station experiments conducted after the main harvest of 2021 in Njoro, Kenya (1800 masl, temperature 17-22 C). Six available dryers were tested: EasyDry (capacity 495 kg, cost of KES 85k), the green house (180 kg, KES 33k), the Multipurpose (90 kg, KES 30k), the POD (90 kg, KES 15k), the Dehytray (7 kg, KES 6k) and the Hybrid (5 kg, KES 17k), and compared to open-air drying (180 kg, KES 5k). In their technical performance, all dryers were faster than open-air drying, which took on average 21.1 h to dry one batch of maize (2.4 h/% point), but only one dryer, EasyDry M500, was substantially faster (8.6 h or 1.03 h/%), as it uses maize cobs for fuel, followed by Dehytray (15.6 h); other dryers took much longer (between 17.6 and 19.9 h). As per the economic analysis, open-air drying was the cheapest drying method, at 0.4 KES/kg maize (US$ 4/tonne). The cost of solar drying strongly decreased with the dryers' capacity, with a cost of 1.4-1.8 KES/kg for the cheapest. Small dryers (<10 kg) were prohibitively expensive and not profitable for routine drying of maize. In conclusion, the dryers tested were economically not competitive with open air drying of maize as they are more expensive, unless other factors are considered, in particular the high drying rate of the EasyDry M500, and the better grain quality of closed systems such as Greenhouse and POD dryers.