Influence of earthworms on organic waste composting and characterisation of vermicompost end products

Abstract

The aim of this work was to study the influence of earthworms on the composting process. Selected waste mixtures pine sawdust + poultry litter (M1), cotton industry waste + poultry litter (M2), shredded paper + horse manure (M3), and cotton industry waste + horse manure (M4) were composted for 85, 64, 60 and 60 days respectively in plastic boxes. The temperature variations during this process followed the typical three-phase pattern. At the end of this process 95, 80, 75 and 95 g of Eisenia andrei were added to each treatment respectively to initiate vermicomposting. Together, the composting and vermicomposting processes took between 105 and 175 days. Earthworm biomass decreased in M1 and M2, and increased in M3 and M4. The physical, chemical and biological variables measured, such as time to compost maturity, the changes in earthworm population, the C/N ratio, and the availability of nutrients, showed that M3 was the best medium for earthworm activity, and that M4 had the best chemical and physical properties as an organic manure. Mixtures containing poultry litter were not suitable for vermicomposting. However, M1 was the best mixture in a test involving the growth of ryegrass (Lolium perenne cv. Weterwald); compared to controls, a 120% dry weight yield was obtained.