Simplified Agri-Innovation for Sustainable Food Systems in Africa

Article Not peer-reviewed version Simplified Agri-Innovation for Sustainable Food Systems in Africa Emmanuel O. Benjamin * , Michael Reuter , Gertrud Buchenrieder Posted Date: 12 August 2025 doi: 10.20944/preprints202508.0855.v1 Keywords: climate-smart agriculture; aquaponics; African catfish ( Clarias Gariepinus ); amaranth ( Amaranthus spp. ); water efficiency; resilience; youth engagement; Africa Preprints.org is a free multidisciplinary platform providing preprint service that is dedicated to making early versions of research outputs permanently available and citable. Preprints posted at Preprints.org appear in Web of Science, Crossref, Google Scholar, Scilit, Europe PMC. Copyright: This open access article is published under a Creative Commons CC BY 4.0 license, which permit the free download, distribution, and reuse, provided that the author and preprint are cited in any reuse. Article Simplified Agri-Innovation for Sustainable Food Systems in Africa Emmanuel O. Benjamin 1, 2,*, Michael Reuter 3 and Gertrud Buchenrieder 2 1 Aglobe Development Center (ADC), Nigeria 2 Universität der Bundeswehr München (UniBw M), Germany 3 Aquaponik-Manufaktur GmbH, Germany * Correspondence: emmanuel.benjami[email protected] Abstract Climate change, resource constraints, and youth disengagement present urgent challenges to African agriculture. This study introduces and evaluates a low-cost, low-energy aquaponics system codeveloped by academia, private sector, and NGOs to enhance climate resilience, nutrition, and livelihoods. Designed for off-grid operation, the system integrates African catfish (Clarias Gariepinus) and Amaranth (Amaranthus spp.) within a simplified, gravity-fed configuration requiring minimal technical skills and capital (less than EUR500). Over a 60-day trial, the system maintained optimal water quality (DO ~4 mg/L; pH ~7; NH₄⁺ <0.05 mg/L), produced optimal Amaranth (Amaranthus spp.) yield, and achieved African catfish (Clarias Gariepinus) growth from 20 g to 125 g with 90% survival. Water use was 3 L/day, underscoring efficiency for drought-prone areas. The systems’ affordability, scalability, and integration into agricultural education position it as a viable climate-smart innovation for smallholder adoption. Policy integration, local manufacturing, and market linkages could accelerate the role of such agri-innovation in transforming African food systems. Keywords: climate-smart agriculture; aquaponics; African catfish (Clarias Gariepinus); amaranth (Amaranthus spp.); water efficiency; resilience; youth engagement; Africa 1. Introduction Climate change represents a critical threat to agricultural productivity across Africa, as shifting climatic patterns increasingly disrupt food systems. The continent has experienced a rise in the frequency and severity of extreme weather events, including prolonged droughts, erratic rainfall, and flooding, which have had detrimental effects on crop yields and overall food security. Ortiz-Bobea et al. (2020) estimate that anthropogenic climate change has reduced global agricultural total factor productivity by approximately 21% since 1961, with disproportionately severe impacts in warmer regions such as sub-Saharan Africa. These challenges are particularly acute for smallholder farmers, who often lack the financial, technical, and infrastructural capacity to adapt to changing conditions (Balgah et al., 2023; Omotoso et al., 2023). Food insecurity remains a persistent concern, as many African countries struggle to produce sufficient food to meet the demands of their rapidly growing populations—limiting not only domestic consumption but also the potential for intra-African trade under conditions of surplus production (Bjornlund et al., 2022). Malnutrition is prevalent, with widespread deficiencies in protein, micronutrients, and vitamin A (Chan et al., 2019). Vegetables and fish are key dietary sources of these nutrients, with fish alone contributing up to 50% of total protein intake in certain African countries (FAO et al., 2020). Nevertheless, per capita consumption of both vegetables and fish remains below global averages and recommended healthy dietary thresholds, resulting in a heavy reliance on imports from outside the continent (Chan et al., 2019; FAO et al., 2020). This dependency highlights the urgent need to strengthen domestic agricultural production and build resilient, self-sustaining food systems. Another pressing challenge lies in youth unemployment and the low appeal of agriculture as a career path for Africa’s growing young Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 Disclaimer/Publisher’s Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content. © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 2 of 13 population (Boye et al., 2023). With millions entering the labor market annually, agriculture holds significant potential to absorb a substantial share of the workforce. Realizing this potential, however, requires deliberate policy interventions to make the sector more attractive and economically viable for youth. Such measures should focus on enhancing access to skills training, innovation, agricultural extension services, capital, and opportunities for private-sector engagement (Boye et al., 2023). Addressing the multifaceted challenges facing African agriculture requires a fundamental paradigm shift in agricultural education. This transformation must prioritize affordable, practiceoriented, innovation-driven, and private sector–aligned approaches that equip both students and farmers with the competencies necessary to succeed in an evolving agricultural landscape (Davis et al., 2008; Mkomwa et al., 2022; Boye et al., 2023). The active engagement of the private sector is pivotal in this process, as it can contribute essential resources, technical expertise, and market linkages that enhance the quality, applicability, and impact of agricultural training programs. Co-creation models such as those advanced in this study are emerging as effective mechanisms for fostering collaboration among diverse stakeholders in agricultural research and development. These models convene students, researchers, and private sector actors to jointly design and implement context-specific solutions, including simplified and cost-effective aquaponics systems tailored to address pressing agricultural constraints. Aquaponics, which integrates recirculating aquaculture systems (RAS) with hydroponics, exemplifies a closed-cycle technology with potential for sustainable food production (Junge et al., 2017; Benjamin, 2020). By embedding participatory approaches and incorporating diverse stakeholder perspectives into agricultural education and research, such innovations can significantly enhance both the relevance and the long-term impact of capacity-building efforts in the sector. This study introduces a simplified aquaponics system specifically designed to overcome the technical complexity and high capital investment that often hinder the adoption of aquaponics technologies. The system incorporates low-energy operation, minimal technical requirements, and an affordable cost structure, making it highly accessible to a wider user base. With setup costs of less than EUR 1,000—including approximately EUR 550 for a 1 m³ fish tank—scalable to support up to 104 m² of grow beds, this innovation offers new opportunities for enhancing food systems in both urban and rural contexts across sub-Saharan Africa. The combination of affordability, scalability, and operational simplicity positions the prototype as an appropriate solution for smallholder farmers as well as educational institutions seeking practical, high-quality training tools. 2. Materials and Methods 2.1.1. Collaborative Development The development of the prototype was the result of a collaborative effort involving the nongovernmental organization Aglobe Development Center (ADC), Nigeria; Aquaponik Manufaktur GmbH; and the University of the Bundeswehr Munich (UniBw M), Germany. Its practical implementation engaged students from the Federal University of Agriculture, Abeokuta (FUNAAB), Nigeria, thereby integrating capacity-building into the project’s execution. The initial conceptual design (Figure 1) was prepared by ADC and subsequently shared with UniBw M and Aquaponik Manufaktur GmbH for technical refinement, leveraging their specialized expertise and experience to optimize the system’s functionality Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 3 of 13 Figure 1. The design and sketch of the simplified aquaponics. 2.1.2. Simplified Aquaponics System and Components A key design requirement for the system is its capacity to function with minimal or no reliance on electricity. This off-grid operational capability is intended not merely as an emergency contingency but as a standard operating mode, ensuring that the physiological and environmental needs of both fish and plants are consistently met. The system is engineered to maintain these conditions even under maximum load, defined as the point at which the established carrying capacity for fish and plants is fully utilized. Fish Tank Specifications The system utilizes an Intermediate Bulk Container (IBC) tank as the primary fish tank (Figure 21), providing a maximum capacity of 1,000 liters. In the operational configuration, 800 liters of this capacity are allocated for system functioning, ensuring optimal water volume for maintaining stable aquaculture conditions. Header Tanks The system incorporates two header tanks, each with a capacity of 200 liters, designed to sustain water circulation for several hours without active pumping. From these tanks, water is directed through the plant grow-bed filtration system and subsequently returned to the fish tank via gravity flow, thereby ensuring continuous nutrient cycling and reducing reliance on external energy inputs. Grow Beds The grow-bed component comprises two Intermediate Bulk Container (IBC) tanks, each modified by removing the top and bottom sections to a height of 30 cm, thereby creating four independent growing units. Collectively, these containers provide an effective cultivation area of approximately 4 m². The beds are filled with a suitable inert medium, such as gravel, which functions as a biofiltration zone. Within this zone, residual organic particles undergo further decomposition, and nitrifying bacteria play a critical role in converting ammonia into nitrate, thereby maintaining water quality essential for plant and fish health. 2.2. Plant and Fish Species Selection The simplified aquaponics system is intended to be cultivated with Amaranth (Amaranthus spp.) and African catfish (Clarias Gariepinus) as the fish species. Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 4 of 13 2.2.1. Crop Variety: Amaranth (Amaranthus spp.) Amaranth (Amaranthus spp.) is among Africa’s indigenous and widely consumed staple vegetables, valued for its ability to supply both macroand micronutrients to millions across the continent. However, despite its prevalence in local diets, its full nutritional potential remains underexploited (Aderibigbe et al., 2022). 2.2.2. Fish Species: African Catfish (Clarias Gariepinus) The African catfish (Clarias gariepinus) has emerged as a species of global significance in the aquaculture industry, particularly in regions where environmental constraints limit the cultivation of other fish species due to its robustness (Benjamin et al. 2020). Its prominence is reinforced by its substantial contribution to local and regional economic development. Nutritionally, C. gariepinus is an excellent source of high-quality protein and essential fatty acids, making it highly valuable for human diets (Onyejiaka & Osuigwe, 2019). Under optimal management conditions, the species can attain marketable size within approximately four months (Benjamin et al., 2021) 2.2.3. The Biological Resilience of African Catfish (Clarias Gariepinus) The African Catfish (Clarias Gariepinus) possesses a unique combination of physiological traits that make it exceptionally suited for low-intensity, resilient aquaculture. This resilience is rooted in its evolutionary adaptations to harsh and variable environments. Facultative Air-Breathing The most significant adaptation of Clarias gariepinus is its ability to breathe atmospheric air. The species has a specialized organ at the gills, which functions as a primitive lung, allowing it to survive for extended periods in water with very low dissolved oxygen (DO) concentrations (Onyejiaka & Osuigwe, 2019). While most cultured fish species require continuous aeration to maintain DO levels above a critical threshold, the African catfish can tolerate DO levels as low as 0-3 mg/L without mortality (Environmental, 2012). Broad Tolerance to Water Quality Parameters Beyond its tolerance to hypoxia, the African catfish exhibits remarkable hardiness across a spectrum of other critical water quality parameters: • Temperature: It thrives in warm water but can endure a wide temperature range from 8°C to 35°C (Environmental, 2012). • pH: While optimal growth occurs in a pH range of 6.5-8.5 (Nugroho et al., 2021), the species can survive in a much broader range, providing a buffer against the natural pH fluctuations inherent in aquaponic systems. • Nitrogenous Wastes: Clarias gariepinus is known for its high resistance to ammonia, the most toxic nitrogenous waste product in aquaculture. While elevated ammonia negatively impacts growth, the species possesses defense mechanisms to cope with concentrations that would be lethal to other fish (Roques et al., 2011). 2.2.4. Implications for System Engineering The unique biology of the African catfish directly informs and validates a simplified engineering approach that would be untenable for most other aquaculture species. • Elimination of Continuous Aeration and Pumping: The ability to breathe air is the single most important trait for manual system design. It obviates the need for continuous mechanical aeration and constant water circulation, which are typically the largest energy consumers in a RAS. This allows for an intermittent flow regime, where water is pumped manually (e.g., twice daily) into header tanks and flows via gravity for a limited period, with extended periods of static water being entirely permissible. Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 5 of 13 • Simplified Filtration and Longer Retention Times: The species' tolerance to ammonia and other waste products allows for a less intensive and more passive filtration design. The system can operate with a much longer hydraulic retention time (HRT)—12 hours or more, as opposed to the 30-60 minutes typical of intensive RAS. This reduces the required flow rate, allowing for smaller pumps and piping, and makes simple, non-pressurized media beds effective as the primary biofilter. • Enhanced System Resilience: A system designed around these principles is inherently resilient. It is not vulnerable to power outages or mechanical failures that would be catastrophic in a conventional RAS. This makes it particularly suitable for off-grid applications or in regions where electricity is unreliable or cost-prohibitive. The selection of Clarias gariepinus is the cornerstone of manual aquaponics design. Its profound biological resilience, particularly its air-breathing capability, makes it possible to engineer a system that is low-cost, low-energy, and robust. This conscious pairing of species and system validates an approach to aquaculture that is accessible, sustainable, and ethically sound, providing a viable food production model for diverse socio-economic contexts. 2.2.5. Flow Rate Management The system’s average flow rate (Q) is not dependent on the biomass requirements but rather by the volume of the header tanks (Vheader) and the duration between successive pumping cycles (tinterval ). Water retained in the header tanks is released by gravity continuously over the entire interval until the subsequent pumping event. The average flow rate is calculated as: 𝑄 = 𝑉ℎ𝑒𝑎𝑑𝑒𝑟 𝑡𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 Using the system operational parameters: 𝑄 = 400 𝐿 7 ℎ × 60 𝑚𝑖𝑛/ℎ ≈ 1 𝐿/𝑚𝑖𝑛 This flow rate represents a fixed parameter inherent to the manual operation and serves as the key determinant of the system’s capacity to process metabolic waste. Thus, the study calculates the maximum mean production rate (Rs,mean) that our fixed flow rate (Q) can support: 𝑅𝑠,𝑚𝑒𝑎𝑛 = 𝑄 × 𝑓𝑡𝑟𝑒𝑎𝑡 × 𝑐𝑠,𝑚𝑎𝑥 For TAN, using the design limit: 𝑅𝑇𝐴𝑁,𝑚𝑒𝑎𝑛 = 0.017 𝐿 𝑠× 0.8 × 3.0 𝑚𝑔 𝐿≈ 0.04 𝑚𝑔 𝑠 This is the maximum mean rate of TAN production that the system can safely process over time. The same process was repeated also for NO2-N, NO3-N and TSS. 2.2.6. Feeding Strategy The maximum permissible daily feeding rate is constrained by the most limiting water quality parameter within the system. Although calculations can be conducted for key substances such as Total Suspended Solids (TSS), nitrite nitrogen (NO₂-N), and nitrate nitrogen (NO₃-N), analyses indicate that Total Ammonia Nitrogen (TAN) serves as the primary limiting factor in determining the design flow rate for systems of this type (Somerville et al., 2014; Bregnballe, 2015). Consequently, the allowable feeding rate is calculated based on the system’s capacity to assimilate and process TAN. The maximum tolerable mean TAN production rate, estimated at 3.46 g/day, directly informs the calculation of the upper daily feeding limit. This requires determining the specific TAN excretion rate per kilogram of feed (RTAN,excr), which is derived from a nitrogen mass balance under a set of defined assumptions (Boyd & Tucker, 2012): Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 6 of 13 • Feed Nitrogen (Nfeed): A standard feed with 42% crude protein is used, where protein is approximately 16% nitrogen. This results in 67.2g of nitrogen per kg of feed. • Fish Nitrogen Content (Nfish): The biomass of African catfish contains approximately 27.5g of nitrogen per kg of fish. • Feed Conversion Ratio (FCR): An FCR of 1.0 is assumed, meaning 1 kg of feed produces 1 kg of fish biomass. This is a value that is quite usual for African Catfish. The nitrogen retained in fish biomass (Nretained) per kg of feed is therefore 27.5g. The total excreted nitrogen (Nexcreted) is the difference between the nitrogen input and the nitrogen retained: 𝑁𝑒𝑥𝑐𝑟𝑒𝑡𝑒𝑑 = 𝑁𝑓𝑒𝑒𝑑 − 𝑁𝑟𝑒𝑡𝑎𝑖𝑛𝑒𝑑 =67.2 𝑔𝑁 𝑘𝑔𝑓𝑒𝑒𝑑 −27.5 𝑔𝑁 𝑘𝑔𝑓𝑒𝑒𝑑 =39.7 𝑔𝑁 𝑘𝑔𝑓𝑒𝑒𝑑 Not all excreted nitrogen is soluble TAN. Assuming approximately 88% of excreted nitrogen is released as TAN, the specific excretion rate is: 𝑅𝑇𝐴𝑁,𝑒𝑥𝑐𝑟 = 𝑁𝑒𝑥𝑐𝑟𝑒𝑡𝑒𝑑 × 0.88 =39.7 𝑔𝑁 𝑘𝑔𝑓𝑒𝑒𝑑 × 0.88 ≈34.9 𝑔𝑁 𝑘𝑔𝑓𝑒𝑒𝑑 With the total daily TAN processing capacity (RTAN,daily) of 3.46 g and the specific excretion rate (RTAN,excr), the maximum daily feed allowance (Rfeed) is calculated: 𝑅𝑓𝑒𝑒𝑑 =𝑅𝑇𝐴𝑁,𝑑𝑎𝑖𝑙𝑦 𝑅𝑇𝐴𝑁,𝑒𝑥𝑐𝑟 =3.46 𝑔 𝑑𝑎𝑦 ⁄ 34.9 𝑔𝑇𝐴𝑁 𝑘𝑔𝑓𝑒𝑒𝑑 ⁄≈100 𝑔𝑓𝑒𝑒𝑑 𝑑𝑎𝑦 ⁄ Therefore, the system is designed to handle a maximum of approximately 100 grams of fish feed per day. 2.2.7. Stocking Density The maximum daily feeding rate determines the total fish biomass (or standing stock, mmax) the system can support. The feeding rate (fr) for catfish is typically between 1-2% of their body weight per day, depending on their size and water temperature. Using the formula 𝑅𝑓𝑒𝑒𝑑 =𝑓𝑟 × 𝑚𝑚𝑎𝑥, we can calculate the maximum biomass: 𝑚𝑚𝑎𝑥 =𝑅𝑓𝑒𝑒𝑑 𝑓𝑟 Assuming an average feeding rate of 1.5% (0.015): 𝑚𝑚𝑎𝑥 =100 𝑔 𝑑𝑎𝑦 ⁄ 0.015𝑑𝑎𝑦−1 ≈ 6.7 𝑘𝑔 With a production volume (V) of 800 L (0.8 m³), the maximum stocking density (dmax) is: 𝑑𝑚𝑎𝑥 =𝑚𝑚𝑎𝑥 𝑉=6.7 𝑘𝑔 0.8 𝑚3≈ 8.4 𝑘𝑔 𝑚3 This calculation confirms that the operational constraints of the manual system naturally lead to a low stocking density (around 8.4 kg/m³), which aligns perfectly with the system's low-intensity philosophy and further reduces stress on the fish. 2.3. Data Collection and Analysis The dataset utilized for the analysis comprises biomass and daily feed weight as well as water quality parameters from a simplified aquaponics system. The students from FUNAAB under the supervision and guidance of the ADC staffs systematically collected this data. 3. Results 3.1. System Operational Performance The preliminary result for the first 60 days are promising results with all components (see Figure 2) performing as anticipated and fulfilling their designated hybrid functions in. Water was pumped Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 7 of 13 from the fish tank to the header tanks twice daily at intervals of approximately seven hours. Efficient settling of larger solids occurred at the base of the header tanks, substantially reducing the organic load entering the grow beds, as predicted. Operating at an average flow rate of approximately 1.0 L/min, the 400-liter capacity of the header tanks facilitated continuous water delivery for roughly seven hours per cycle. The observed average flow rate of 0.25 L/min to each media bed corresponds well with the system’s overall design flow rate of 1.0 L/min. The mean flow rate resulted in a hydraulic retention time (HRT) in the media beds of approximately 2 hours. This was long enough to reliably ensure the removal of the organic load and maintain biological filtration (i.e., nitrification). At the same time, the plants were continuously supplied with nutrients. This also enabled the simplified aquaponics system to sustain continuous water flow to both the grow beds and fish tank for a cumulative duration of 14 hours per day, notwithstanding notable fluctuations in flow rate resulting from variations in the hydraulic head within the header tanks. During the remaining 10 hours, primarily overnight, water flow was minimal or ceased altogether. The intermittent flow regime posed no discernible risk to either the African catfish (Clarias gariepinus) or the cultivated amaranth (Amaranthus spp.), owing to stable water retention in the media beds and reduced metabolic demands associated with lower ambient temperatures during nighttime. Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license. 8 of 13 Figure 2. Test running of the simplified aquaponics at ADC 2025. 3.1.1. Core Physiochemical Parameters Dissolved oxygen (DO) levels were consistently maintained near 4 mg/L, a concentration sufficient to support the physiological requirements of aquatic organisms as well as the aerobic microbial communities critical for processes such as nitrification. The system’s pH remained stable at approximately 7 throughout the monitoring period, aligning with the optimal range for efficient plant nutrient assimilation and microbial activity, particularly favoring nitrifying bacteria that thrive in neutral to slightly alkaline environments (see Figure 3). Ammonium (NH₄⁺) concentrations were measured at below 0.05 mg/L and exhibited a decreasing trend during the preliminary operational phase. This decline suggests active biological conversion of ammonium to nitrite and subsequently to nitrate, indicating a functional and efficient nitrification process within the biofilter or root zone microbiome. Figure 3. DO, pH and Ammonium values for second month of prototype operations. 3.1.2. Water Consumption The actual water replacement within the system was 3 liters per day with stable water quality parameters, underscoring the robustness and efficacy of the integrated plant filtration component. This performance highlights the advantages of the closed-loop aquaponics design, where nutrient cycling and waste assimilation occur synergistically, minimizing the need for frequent water renewal. The plant biofilter effectively removed organic contaminants and metabolized nitrogenous wastes, thereby sustaining a balanced aquatic environment conducive to both fish health and plant growth 3.2. Plant Production Performance (Amaranthus spp.) After 45 days of cultivation, Amaranthus spp. plants demonstrated robust growth, reaching an average height of 90 cm and producing approximately 255 leaves per plant (see Figure 2 above). 3.3. Fish Production Performance (Clarias gariepinus) The initial mean individual weight of the African catfish (Clarias gariepinus) at stocking was approximately 20 grams, which increased to an average of 125 grams over a 60-day cultivation period, accompanied by a high survival rate of 90%. These growth performance metrics underscore the system’s efficiency and robustness. Based on these results, a projected biomass yield of above 250 g/m³ is both realistic and attainable within this production framework. Preliminary data also indicate 0 1 2 3 4 5 6 7 8 9 0 5 10 15 20 25 30 DO pH NH4-N Preprints.org (www.preprints.org) | NOT PEER-REVIEWED | Posted: Posted: 12 August 2025 doi:10.20944/preprints202508.0855.v1 © 2025 by the author(s). Distributed under a Creative Commons CC BY license.