Creating a Zero-Waste, Circular Nation
Singapore has demonstrated the ability of co-digestion systems to bring cities closer to achieving energy self-sufficiency in used water treatment.
Globally, if all available sewage generated by the entire world was collected and treated via anaerobic digestion, there is a potential to generate 210–300 TWh of energy which can meet the needs of 27–38 million people around the world. Meanwhile, if all available food waste/loss was collected and recycled via anaerobic digestion, there is the potential to generate 880 to 1,100 TWh of energy, which can meet the electricity needs of 112–135 million people.
Singapore co-digesting the future
Singapore has recently trialled a project to co-digest food waste and used water sludge with results indicating the process can triple biogas yield, compared to the treatment of used water sludge alone. Over a 2-year period, Singapore’s Public Utilities Board (PUB) and the National Environment Agency (NEA) explored the viability of collecting and transporting source-segregated food waste from various premises to the demonstration facility at the Ulu Pandan Water Reclamation Plant for co-digestion with used water sludge.
As part of the trial, up to 40 tons of used water sludge and food waste from 23 premises were treated daily at the facility. Results showed that the synergistic effects in the co-digestion of used water sludge and food waste can increase biogas production by up to 40% compared to the separate digestion of the two inputs.
Moving forward, the co-digestion of food waste and used water sludge will be implemented at the new Integrated Waste Management Facility and Tuas Water Reclamation Plant, which combined is known as the Tuas Nexus, which are scheduled to be completed in 2025.
Conclusion
Cities can unlock the potential of biogas to become energy self-sufficient.