Overview
- Pilot results published in the Chemical Engineering Journal show about 200% more renewable natural gas from sewage sludge and nearly 50% lower final disposal costs compared with current practice.
- APAD uses a high-pressure oxygen pretreatment that breaks tough organics before digestion, raising carbon conversion to about 62% for residual sludge and boosting methane output from that step by up to 79%.
- A biological upgrade then employs a newly patented methanogen with hydrogen to convert CO2 into methane, delivering pipeline-compatible gas with CO2 at or below 3% and doubling total methane production.
- Economics remain mixed as pretreatment alone cut sludge treatment costs from $494 to $253 per ton, while the full APAD rose to about $530 per ton because the upgrade relies on purchased hydrogen.
- The WSU-led team, which includes partners at Pacific Northwest National Laboratory and Clean-Vantage, is working with an industrial partner to scale the system, aiming to turn energy-hungry wastewater plants into local renewable gas sources if low-cost hydrogen becomes available.