Evolution of Microbial Load and Physicochemical Parameters during The Composting Process Using Grass Clippings and Cocoa Pod Husks

Abstract

Composting is a biological process that supports the recycling of agricultural and green wastes into organic amendments. This study evaluated changes in microbial load and selected physicochemical parameters during the composting of grass clippings and cocoa pod husks. A compost pile was prepared at Nangui Abrogoua University, Abidjan, Côte d’Ivoire, using 50 kg of grass clippings and 50 kg of crushed cocoa pod husks. Samples were collected at six time points to monitor lactic acid bacteria, yeasts, moulds, and bacteria of the genus Bacillus. Temperature, pH, moisture content, carbon, nitrogen, phosphorus, potassium, organic matter, and the C/N ratio were also measured. The temperature increased from 28°C on Day 0 to 59.36°C on Day 11 and remained high on Day 31, with a value of 56.46°C, before decreasing to 25.04°C on Day 120. Moisture content varied from 72% at the beginning to 78.2% at the end of composting. The pH remained alkaline during most of the process but decreased from 8.7 on Day 0 to 7.57 on Day 120. Microbial populations changed with temperature, and yeasts disappeared during the thermophilic phase. Bacillus remained the dominant microbial group across the sampling periods. At the end of composting, phosphorus increased from 0.18% to 0.369% and potassium from 2.86% to 3.53%, whereas carbon, organic matter, nitrogen, and the C/N ratio decreased. The final C/N ratio was 20.09, indicating progression towards compost maturity. These findings show that grass clippings and cocoa pod husks underwent measurable biological and physicochemical changes during composting.