Optimizing food market waste composting parameters for the production of organic fertilizer using response surface methodology in Dodoma, Tanzania

Abstract

As Africa’s population grows, the challenges of managing municipal solid waste and maintaining soil fertility are becoming increasingly intense. In Tanzania, over 60% of municipal solid waste is improperly handled, exacerbating environmental degradation and resource loss. This study investigates the optimization of food market waste composting to produce nutrient-rich organic fertilizer, using response surface methodology to evaluate the effects of moisture content (45–75%) and pH (4–6.5). The composting process involved 13 reactors, with peak temperatures of 56.4 °C achieved within 7 days, ensuring the inactivation of pathogens. Optimal conditions were determined to be 60% moisture content and an initial pH of 5.2. Compost produced under these conditions contained maximum nutrients: 1.49% total nitrogen, 0.38% available phosphorus, and 0.82% potassium. The compost exhibited a high germination index (98%) for Raphanus sativus seeds, indicating the absence of phytotoxicity and suitability for agricultural use. Key maturation indices, including pH, total organic carbon (TOC), and the C:N ratio, reflect successful stabilization and humification during the 49-day composting period. The TOC decreased from 40.2% to below 10%, and the C:N ratio dropped from 28 to 8, demonstrating organic matter mineralization. The quadratic models developed through response surface methodology exhibited high accuracy, with R2 values ranging from 0.88 to 0.96. This study highlights the potential for transforming food waste into high-quality organic fertilizer, offering sustainable solutions for waste management and improving soil fertility in developing countries. These findings contribute to advancing circular economy principles and provide valuable guidelines for scaling up composting practices.