Composting versus vermicomposting: a comparative study of organic matter evolution through straight and combined processes.

Changes in physical and chemical characteristics of an organic waste (tomato crop waste) throughout composting (COM), vermicomposting (VER) and the combination of both processes (C+V) were assessed at five selected stages. COM consisted of a combination of the static Rutgers system with forced aeration and pile turning. For VER Eisenia worms were fed with the raw material. For C+V pre-composted material was added to the worms. Particle size decreased during COM, yet it increased during VER and C+V due to the amalgamation of small particles. pH was alkaline throughout the processes. Heavy irrigation during vermicomposting resulted in greater decrease of EC and greater leaching of organic matter, total nitrogen and most macronutrients in VER and C+V than in COM. Final materials were not phytotoxic but compost could have salinity related problems. Thus, COM, VER and C+V produced treated organic material, which could be suitable for horticultural purposes.