Utilisation of palm oil mill wastes to make soil conditioner through anaerobic co-composting is feasible and has the potential to maintain the natural resources, and to reduce the impact on environmental quality in the future. Co-composting process uses pressed-shredded-grinded empty fruit bunch (EFB) with activated sludge (AS) from the pond system of a palm oil mill as a suitable option for organic waste disposal with economic and environmental profits, since the process leads to stabilised final compost which can be used to improve and maintain soil quality, and fertility. The temperature, pH, electrical conductivity and moisture profile in the compost was analysed during the experiment. The pH and moisture values remained stable within 6.8%–9.2% and 64%–71% throughout the process. The final matured compost was deemed stable for agricultural uses considering C/N ratio of 12.2 achieved within 100 days. The amount of nutrients and heavy metals were analysed in the final matured compost.