THE EFFECT OF PHOSPHATE AND ORGANIC ADDITIVES ON THE STABILITY OF FOOD WASTE IN THE FULL-SCALE COMPOSTING

Food waste was composted with three additives consisting of phosphate sludge, green waste, and olive mill waste to produce a stable compost. To determine the stability for agricultural utilization, the compost maturity was evaluated using physic-chemical parameters. The temperature of treated composts remained high in the first month of composting. However, the pH was increased during composting to a slightly alkaline level around 8.0 instead of 9.31 in the control of food waste only. The integration of additives into the food waste composting has considerably reduced the electrical conductivity of the piles to optimal values less than 4 mS/cm. The C/N ratio decreased to less than 10 after 150 days, but the C/N ratio of the control (17.37) was two times higher than the enriched composts with additives composting indicating a good maturity of the composts enriched with additives. In addition, the additives significantly improved the stability of food waste during composting; the composts enriched with additives were thermostable more than 0.5 times than the control. The additive composed by a combination of phosphate sludge and olive oil mill waste showed greater effect on maturity and stability of the compost produced compared to other additives of only phosphate sludge and phosphate sludge + green waste.