Composting wet olive husks with a starter based on oil-depleted husks enhances compost humification

Wet olive husks represent an environmental problem in Mediterranean areas but also a potential resource as recyclable organic matter. In the present work, we describe the composting of wet olive husks, using mechanically turned piles without forced ventilation, carried out to study the effects of partially composted oil-depleted husks as a starter for wet husks degradation. At the beginning of the composting process, protease and dehydrogenase activity, along with the microbial respiration, were higher in the piles with the starter, demonstrating a higher microbial activity in comparison with the piles without the starter. At the end of the process, the compost with the starter showed a deeper humification and a lower content of total organic carbon with respect to the compost without the starter, indicating a higher level of biodegradation and organic matter evolution. The main outcome of this research include the possibility to: (a) detoxify and de-odorize a bad-smelling waste into an hygienically safe product; (b) produce a green, mature, humified compost useful to restore soil fertility and texture in intensive and organic agriculture.