GreenCouple project

Challenge

Wastewater treatment plants (WWTPs) have a significant potential to reduce energy consumption and produce renewable energy through anaerobic digestion (AD) of sludge. Yet, only around 10% of European WWTPs currently generate biogas, due to the decentralized nature and varying sizes of plants, which limits the economic viability of AD.

In addition, current biogas valorisation strategies, such as combustion in boilers, CHP engines, or enrichment to biomethane, leave considerable opportunities untapped. Purifying biogas and reintegrating it efficiently into WWTP processes remains a major technical and economic challenge. Sustainable, low-cost solutions for digestate and biogas treatment are urgently needed to reduce environmental impact, cut operational costs, and accelerate the adoption of renewable energy technologies in wastewater treatment.

Our Solution

The LIFE GreenCouple project addresses these challenges by developing nature-based and low-cost solutions to enhance digestate and biogas valorisation. Our approach integrates two complementary biotechnologies:

• Constructed Wetlands (CW): an innovative Nature-Based Solution for pre-treating digestate centrate, removing phosphorus, contaminants of emerging concern, and producing a biogenic nitrate/nitrite-rich stream.
• Suspended Biomass Bioreactor (SBB): an anoxic bioreactor that uses the treated centrate to biologically remove hydrogen sulfide (H₂S) from biogas, reducing operational costs of current purification methods.

The LIFE GreenCouple solution will be scaled up and validated at three demo sites across Spain and Ireland, demonstrating a cost-effective, sustainable pathway for biogas purification and digestate treatment. By integrating nature-based treatment, innovative bioreactor technology, and process optimization, LIFE GreenCouple aims to unlock the full potential of AD, advancing circular economy practices in wastewater treatment and foster future downstream biogas valorisation technologies.

Timeline

• September 2026: LCAs framework of LIFE GreenCouple issued.
• December 2026: Prototypes A built and commissioned in Gandia WWTP.
• February 2027: Prototype B built and commissioned in Ontinyent WWTP; start monitoring the evolution of microbial consortium in biotechnologies.
• December 2028: Prototype B installed in Huntstown AD plant.
• September 2029: Final project event.