Organic fertiliser production through bioconversion of industrial plant and Nile perch solid bi-products in Uganda

Abstract

The study sought to explore sustainable waste management by converting plant and Nile Perch solid industrial bi-products into nutrient-rich organic fertilisers. The research was conducted around Lake Victoria in Uganda, targeting the Nile Perch fish processing industries. Solid fish waste was mixed with sawdust and coffee husks, then processed using three composting methods; natural, Indigenous Microorganisms (IMO) and anaerobic composting. Nutrient profiling of the raw materials and the resulting fertilisers was conducted, focusing on nitrogen (N), phosphorus (P), potassium (K), carbon (C). Natural composting and use of IMO methods produced solid fertilisers with significantly higher NPK values compared to anaerobic production methods. For fertilisers produced using ratio 1, the highest nitrogen content (2.75%) was recorded in IMO composting, followed closely by natural composting (2.74%), both exceeding the levels found in commercial and anaerobic composts. Phosphorus and potassium levels followed a similar trend, with IMO compost yielding 2.02% phosphorus and 2.23% potassium. For fertilisers produced using ratio 2, natural and IMO composts again outperformed other methods, with potassium content reaching 2.54% and 2.23% respectively critical for fruiting and yield. Additionally, the C:N ratios in IMO and natural composts ranged between 13:1 to 17:1, falling within or near the optimal range for effective nutrient mineralisation and plant uptake. The study concluded that Nile Perch industrial bi-products, when appropriately processed with plant bi-products, particularly through IMO and natural composting they offer high-quality organic fertilisers. This not only mitigates environmental pollution but also offers a sustainable, high-quality alternative to inorganic fertilisers for crop productivity in Uganda.