Co-composting of spent coffee ground with olive mill wastewater sludge and poultry manure and effect of Trametes versicolor inoculation on the compost maturity

► Coffee ground, olive mill wastewater sludge and poultry manure were co-composted. ► Effect of Trametes versicolor on the humification process was investigated. ► Compost was mature with germination index of 120% after 20 wk composting. ► Inoculation improved 1.75 times humic acid production at the end of the process. ► Polyphenols and lignin were also reduced by 72% and 51% respectively.