Comparative Study of Cooked and Uncooked Food Waste Co-composting with Green Waste and Sewage Sludge: A Case Study of Tunisia

Worldwide, substantial quantities of food waste are produced daily causing several environmental issues, such as the need for large landfills and significant spending for them to be well-managed. So, the development of novel processes to handle this alarming organic waste problem seems to be urgent. Its conversion into value-added products is ensured by aerobic digestion. That kind of process decreases the need for chemical fertilizers and the degradation of the soil by biofertilizer production. This work aims to evaluate the effect of cooked and uncooked food waste when it is co-composted with sewage sludge and green waste. Two windrows (A1 and A2) were conducted during 14 weeks, in which sewage sludge (SS) and green waste (GW) were mixed at the same ratio of 25% with uncooked food waste (UFW) and cooked food waste (CFW) to form A1 and A2, respectively. Several parameters, such as temperature, pH, Total Organic Carbon (TOC), Total Nitrogen (TN), and C:N ratio, were monitored to evaluate the co-composting experiments and its evolution during the whole process. Results show that windrow containing CFW reached 62 °C only two days after its setting-up and the thermophilic phase lasted 15 days. However, for the windrow containing UFW, the maximum temperature reached was 59 °C after four days, and the thermophilic phase lasted 14 days. During the thermophilic phase of A1 and A2, temperature was above 50 °C. Temperature and C:N ratios acted as a detector of the stability and the maturity of the obtained end-product.