The mixtures produced were placed in 350-L thermo-composters made of high-density polyethylene (HDPE) and with a lateral system of natural ventilation to guarantee aerobic conditions; in each thermo-composter were installed probes for automatic monitoring of the temperature. The piles were turned when the temperature in the mixtures decreased, to provide aeration and to improve the homogeneity of the materials, thus favouring the composting process. Each pile was turned 2–3 times depending on the development of the temperature; piles 1 and 2 were turned twice (at 10 and 31 days) and piles 3 and 4 were turned three times (at 5, 14 and 33 days). The moisture content was maintained within the range 40–70%, as determined in samples collected periodically. According to previous composting studies, very-low moisture values (70%) may produce anaerobic conditions due to waterlogging (Tiquia et al., 1998). The bio-oxidative phase of composting was considered finished when the temperature was close to the ambient and re-heating after turning did not occur. Then, the composts were left to mature over a period of one month, approximately.