NexusHub – Concept for the implementation of a collaborative demonstration project related to the Water-Energy-Food Nexus with partners from Sub-Saharan Africa

Hydroponic plant cultivation is a water-, nutrient- and space-efficient way to produce fresh food. Usually, mineral nutrient salts are used for this purpose, which are easy to dose and can also be adjusted depending on the plant and growth stage. However, these nutrient salts are expensive to purchase and not always available. Particularly in arid and rural regions of Kenya, where food shortages and crop failures due to drought have occurred over the past years, farmers face major challenges in terms of water shortages as well as severe price fluctuations of fertilizers. In addition, many communities in rural Kenya have no or very limited access to energy.

Thanks to solar power: Decentralized and sustainable system solution

The aim of the NexusHub project, which is funded by the Fraunhofer-Zukunftsstiftung (Fraunhofer Future Foundation), is to develop a decentralized system solution powered by photovoltaics (PV) that can be deployed to contribute to energy and food security in rural regions of Kenya. Among other things, mineral fertilizer is to be replaced by organic-based fertilizer from locally available and processed waste materials. PV systems provide the electricity required for processing the organic waste materials and for cultivating market-relevant products (coriander, kale) in the hydroponic system. Surplus electricity can additionally be used for other productive activities.

Nutrient solution through combined processing of residual materials

In NexusHub, we are investigating various organic resources (plant and animal residues) and processing steps for their suitability to produce a hydroponic nutrient solution for coriander and kale. The residues are first anaerobically digested for several days and then biologically treated in a sequencing batch reactor (SBR). These processes are designed to ensure conversion to nutrients in a plant-available form. Subsequently, the effect of the produced nutrient solution on plant growth is tested in the NFT system (nutrient film technique).

Energy self-sufficient due to photovoltaics

To operate the processing and planting systems, a PV-based energy generation and storage system is being developed by Fraunhofer ICT. An overreaching Arduino control system, developed by the Jomo Kenyatta University of Agriculture and Technology (JKUAT) controls the individual components on the basis of data collected by sensors. The developed system makes it possible to generate energy and food in remote regions year-round in a sustainable and resource-efficient manner. In addition to the system in Germany, a demonstrator was also developed in Nairobi.

Scale-up according to demand: for small and large scale applications          

The system can be scaled at different levels. Thus, the process is suitable for subsistence farming, small cooperatives as well as large-scale commercial cultivation. At the prototypes in Stuttgart and in Nairobi, we are currently working on process optimizations for the generation of the nutrient solution as well as energy management. In the next step, we aim to scale up and implement the system in a village community in rural Kenya.