Browsing by Author "Louw, Christina Alet"

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    Feasibility assessment of biogas-fuelled refrigeration to curb spoilage in food value chains in Sub-Saharan Africa
    (2023-03) Louw, Christina Alet; Van Rensburg, Eugene; Görgens, Johann Ferdinand; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering.
    ENGLISH ABSTRACT: he lack of access to refrigeration in Sub-Saharan Africa (SSA) due to deficient electrical grids is a major contributor to food loss, which exasperates food insecurity in the region. The use of biogas-fuelled refrigeration (BFR) could provide opportunities to leapfrog over environmentally harmful or outdated refrigeration methods while curbing food loss and treating organic waste. The main objective of this research was to evaluate the applicability and feasibility of BFR in SSA. This project compiled findings from value chain analyses (VCA) in literature of the beef, dairy, fish, and fruit and vegetable value chains in SSA to describe the nature and distribution of food loss and available feedstocks for anaerobic digestion. The analysis found that food loss is concentrated in the processing, agricultural production, distribution, and postharvest handling stages of the fruit and vegetable, meat, fish, and dairy value chains, respectively. However, regardless of the distribution of the losses, refrigeration intervention measures early in the value chain could mitigate downstream food losses. BFR could also only be implemented where there is sufficient feedstock and has limited impact on food loss mitigation in cases where other problems with food handling cause food loss regardless of access to refrigeration. Using these findings from the VCA, scenarios where waste would be readily available or where multiple stages in the value chain could be targeted were chosen as the foundations for BFR process models, namely a dairy farm, abattoir, and a community setting. The process models investigated were absorption dairy coolers for dairy smallholders, containerized compression refrigerated cool rooms for small-scale actors in the fruit and vegetable value chain, industrial icemakers to supply ice to small-scale actors in the fish value chain, and combined heat and power (CHP) systems to cover the electrical requirements of refrigeration for modernised abattoirs. Four feedstocks associated with the value chains were selected for biomethane potential (BMP) testing: fruit and vegetable waste, tomato waste, abattoir waste, and cow manure. The BMP results were used as a basis for sizing the required biogas installations to meet the calculated energy requirements of the various refrigeration systems. The capital (CAPEX) and operating costs were estimated using capacity-cost estimations based on collated data of existing biogas installations in SSA. When electricity generation was required to drive the refrigeration process, multivariate regression was used to develop a model that estimated the CAPEX of a plant based on the volume of the digester and its electrical output. Using discounted cashflow analysis of the scenarios at various scales, internal rates of return (IRRs) ranging from 15.13% to 28.16% (absorption cooler), -6.77% to -2.79% (CHP), 0.97% to 22.84% (cool room), and 0.74% to 24.05% (ice maker plants) were estimated. Issues arose with feedstock availability, particularly for the large-scale processes which would benefit the most from economies of scale. Income and earnings through savings from the waste treatment were shown to substantially improve process profitability. Challenges to implementing BFR include feedstock availability, training and maintenance requirements, access to water, and high upfront costs.