• supressive compost
• Olive husk
• microbial inoculum
• composting

The olive humid husk (OHH) is the main solid by-product derived from the olive oil industry. The treatment and disposal of this biomass is difficult because its high moisture and its high content of mineral salts, phenols, lipids and organic acids that makes it a phytotoxic material. Among the available technologies to dispose this waste, composting has been considered the best solution due to its low cost and benefits for the agriculture. The composted OHH returns to croplands the organic matter and nutrients lost by intensive cultivation and avoids at the same time some of the drawbacks often observed when OHH is directly applied to the soil. However, due to the high content of lignocellulosic materials, oil, and antimicrobial compounds, OHH composting is a difficult slow process, not suitable for the industry.
In the current research, looking for the production of a green composted amendment, thirteen microorganisms were specifically selected to enhance OHH degradation. The selected microorganisms were then utilized as inoculum in a composting trial that was carried out in dynamic turned Piles. The results indicated that microbial inoculation accelerates the degradation of OHH, reducing the time of composting. In addition, the microbial inoculum had a positive influence on compost quality. The final product showed a deeper humification and better detoxification.
Besides, with the aim to improve the suppressive properties of compost, the biocontrol strain B. subtillis M51/II was included in the microbial consortium of the inoculum. The persistence of the strain during the whole composting process was monitored using together a selective microbial analysis and a specific colony PCR assay. The results indicated that the strain B. subtillis M51/II was not only able to survive to the composting process but also able to increase its density.
In this thesis, for the first time, it has been set up a procedure for the production of a high quality green composted amendment from OHH in a relatively short time. Besides, the results shows that the use of a microbial inoculum for the production of OHH compost could be successful as a good delivery system to introduce the microbial biocontrol strain B. subtillis into the soil.