The availability of on-farm storage and processing is a critical challenge facing small farmers, which hinders agricultural productivity. Thirty per cent of the food produced globally is lost after harvest, with the proportion being exceptionally high in low- and middle-income countries due to a lack of on-farm handling and storage facilities. Conventional cold-storage solutions have not taken off at the smallholder level, mainly due to a lack of availability and access to reliable grid electricity. Therefore, off-grid decentralized solar-powered cold-storage units can play a vital role in preserving the produce at production sites and enhancing livelihood and rural development with a minimal carbon footprint. To maintain low temperatures at every step of the agricultural value chain, known as the ‘cold chain’, several technology vendors aim to improve the shelf life and user benefit. Small-scale farmers, which account for two-thirds of all food losses, are another group they focus on. This study examines the existing situation, importance and potential opportunities of decentralized cold-storage systems for fresh fruit and vegetables. In addition to economic, social, technological and environmental limitations, this study examines the triumphs and challenges of incorporating solar-energy-powered cold storage into developing communities. Although the private sector, NGOs and some government agencies are working to promote decentralized cold-storage facilities, relatively little has been done so far to have a significant influence on post-harvest losses and food security. There are still knowledge gaps on decentralized cold-storage facilities. The primary operational constraint is the economic situation of end users and the lack of financing alternatives for smallholder farmers.

In a number of tropical countries, the expansion of cassava processing is tied to the development of small-scale, energy-efficient pneumatic dryers used to dry flour and starch. To facilitate this development, in this study a model of the pneumatic drying of starch particles was developed, to be fitted to measurements taken from large cassava processing factories. After that, numerical simulations were performed to analyze the effects of geometry and operating conditions on the energy efficiency and pipe length required to dry the product. The results clarified the influence of processing capacity, air inlet conditions, and starch particle size, emphasizing that air velocity as well as the dilution of the starch should be minimized. In light of the findings described here, we offer guidelines for the design of efficient small-capacity flash dryers.

Small-size enterprises drying cassava in Africa mostly use fixed-bed dryers or pneumatic dryers. The objective of this study was to determine which of those two dryers is the best choice for this operation. Energy performance, product quality and costs were measured and analysed using a comparative experiment design. Each dryer was considered as a treatment and experiments were performed in quintuplicate at a cassava processing small-size enterprise in Ghana. The energy performance of the pneumatic dryer was superior because of the better contact between the cassava grits and the drying air, resulting in greater heat and mass transfer. The cassava flour obtained from the fixed-bed dryer had a higher Whiteness Index, but the same level of lightness, and the staff responsible for managing product quality was not able to visually distinguish them. As a result of the pneumatic dryer’s better energy performance, its operating cost was lower. The capital cost of this dryer was higher, but to recover the additional investment only 194 days of operation were needed. Therefore, it was concluded that pneumatic dryers are a better choice of equipment for cassava drying by small-size enterprises in Africa.

The development and scaling out of flash-dryer innovations for more efficient, small-scale production of high-quality cassava flour (HQCF) and starch is described. The diagnoses of cassava-processing SMEs (small and medium enterprises) revealed their energy expenditures for drying were considerably higher than those of large-scale industrial companies, which was mostly due to suboptimal design of flash-drying systems. As a result, small-scale production of cassava starch and HQCF often incurs high production costs, incompatible with market prices of final products. Taking stock of this situation, RTB scientists have developed several innovations to optimize energy efficiency and costs, including a longer drying pipe, reengineered heat exchanger, larger blower for higher air velocity, and a higher product/air ratio. This was based on numerical modelling to determine the key design features of energy-efficient flash dryers, followed by construction and demonstration of a pilot-scale prototype. As a result, improved small-scale flash dryers are now being scaled out to the private sector in various countries, using the Scaling Readiness framework and achieving 10–15% gains in productivity and incomes. A method for diagnosis of process efficiency is also described, to identify technical bottlenecks and to document and measure the outcomes and impacts during the implementation of scaling-out projects.