Value Addition of Cow Dung Compost through Single Screw Extrusion Process

Background: Single-screw extrusion is an innovative method for improving cow dung composting and addressing traditional challenges like nutrient loss. Single-screw extrusion significantly enhances cow dung composting by improving nutrient retention (notably N and P) and accelerating decomposition. Methods: Fresh cow dung was processed through traditional composting and single-screw extrusion composting and fresh cow dung was used as a control. The extrusion process employed optimized mechanical parameters (600 rpm screw speed) before composting. The compost pit was monitored throughout the 3-month process. The temperature averaged 34oC initially, peaked at 62oC during the thermophilic phase and stabilized at 32oC during maturation, confirming successful decomposition. All treatments were analyzed for moisture content, C: N ratio, ash, organic matter, macronutrients (N, P, K, S) and heavy metals (Cd, Cr, Ni). Statistical comparison (ANOVA, p less than 0.05) also determined significant differences between processing methods. Result: The study found that moisture reduction (25%) and a declining C: N ratio (from ~38 to less than 20) reflected intense microbial activity, while pH stabilization (7.16) indicated compost maturity, with optimal moisture, aeration and nutrient balance ensuring efficient decomposition. Conventional composting resulted in substantial nutrient losses, with nitrogen (N) decreasing by 16.4% (from 1.22% to 1.02%), phosphorus (P) by 7.4% (from 0.27% to 0.25%), potassium (K) by 52.2% (from 0.69% to 0.33%) and sulfur (S) by 34.0% (from 1.03% to 0.68%). In contrast, single-screw extrusion significantly improved nutrient recovery, increasing N by 26.2% (from 1.22% to 1.54%) and P by 11.1% (from 0.27% to 0.30%), while still showing reductions in K by 49.2% (from 0.69% to 0.35%) and S by 34.0% (from 1.03% to 0.68%). Micronutrient analysis revealed stable zinc levels (0.01%), a threefold increase in copper from 0.001% to 0.003% and a doubling of boron levels (from 0.001% to 0.002%) in extruded compost, revealing enhanced nutrient concentration during extrusion. These findings highlight extrusion composting as a promising method for nutrient retention and compost quality improvement.