Influence of mixing ratio and turning frequency on the co-composting of biowaste with sugarcane filter cake: a mixture experimental design

Although composting is an effective option for the use of biowaste (BW), its physicochemical quality has limiting conditions (e.g., low C/N ratio, phosphorus and high moisture) that affect the process and the quality of the product. The incorporation of amendment materials (AM) and the variation in the turning frequency (TF) are two of the most widely used operational strategies to improve these limiting conditions. However, the effect of the simultaneous application of these two strategies on the BW composting process has been few studied. In this article, the inclusion of sugarcane filter-cake (SFC) as an AM in BW at several mixing ratios (BW:SFC (w/w); 100:00, 90:10, 80:20 and 70:30) and three TFs (1, 2 and 3 turnings/week) was evaluated at a pilot scale. A Box-Behnken experimental design was used to analyse the simultaneous effects of the two strategies. Results showed that the application of both operational strategies simultaneously has a significant effect (p <= 0.05) on process parameters [i.e., stabilization time, temperature, pH, oxygen concentration, Total Organic Carbon (TOC), Total Nitrogen (TN) and Total Phosphorus (TP)] and on product quality. A mixture ratio of 80:20% (BW:SFC) and a TF of 2 reduced processing time by 13 days compared to the control treatment, maintained temperatures above 65 degrees C and increased the TOC (> 15%), TN (2.4%) and TP (1.6%) contents at the end of the composting process, thus improving the quality of the final product.