Integrated optimization of poultry waste conversion into biofertilizer and biogas for sustainable tomato cultivation

Abstract

Sustainable tomato production increasingly requires efficient and environmentally responsible fertilization strategies. In this context, poultry waste valorisation through anaerobic digestion (AD) offers a promising route to produce nutrient-rich biofertilizers while generating renewable energy. The present study investigated the combined effects of key AD factors on both biogas yield and digestate quality intended for horticultural use. Four factors were examined using a 2⁴ factorial design: temperature, moisture, molasses addition, and Aspergillus niger inoculation, resulting in sixteen combinations. The mixtures underwent a 21-day methanization process. Comprehensive physicochemical and nutritional analyses were conducted, followed by a tomato fertilization test to assess agronomic performance. Fungal inoculation exerted the strongest positive effect on process efficiency. Temperature enhanced potassium availability, whereas excessive moisture limited total organic carbon degradation. Mixture M12 produced the highest biogas yield (>17,000 mL) and exhibited balanced nutrient contents (N 1.45%, P 1.98%, K 2.5%). Its digestate improved tomato growth, outperforming the control and approaching the performance of chemical fertilizer. Optimisation of the AD process therefore supports sustainable horticultural production while contributing to waste reduction and renewable energy recovery