Nutrient carrier minerals for efficient and circular use of phosphorus in tropical crop production systems

Mineral P fertilizers play a crucial role in overcoming P deficiency and safeguarding agricultural productivity. Yet, in sub-Saharan Africa (SSA), where P-depleted weathered soils are widespread, access to mineral fertilizers by smallholder farmers is limited. Yet at the same time, urban environments in SSA are facing widespread eutrophication due to a lack of wastewater treatment. The general objective of this project is to develop a low-cost technology that facilitates the recycling of P from wastewater into fertiliser products, thereby promoting a circular economy, and at the same time, contributing to enhanced food security. The innovative approach is based on layered double hydroxides (LDHs), with a technology that has been developed in the host group of the applicant. The LDHs can act as a selective adsorbent for P in liquid biowaste streams, and the P-loaded LDH is an excellent P fertilizer in acid weathered soils. Here, LDHs will be prepared via the mechanochemical treatment of locally-available resources, i.e. weathered soil as a source of Fe/Al, and lime/alkali. These LDHs will be evaluated for P adsorption from liquid biowaste streams. The fertilizer value of the recycled P products in weathered soils will be investigated in extraction tests, soil incubation experiments, and greenhouse trials. Finally, the P recycling technology will be demonstrated in Madagascar with pilot-scale P recovery from wastewater and the subsequent use of P-loaded LDH in a field trial.