LIFE GreenCouple

Sustainable biogas purification through the integration of a nature-based solution for digestate liquid fraction treatment with biological H2S removal

The LIFE GreenCouple project addresses one of the current challenges of the urban water cycle: improving the environmental and energy sustainability of wastewater treatment plants (WWTPs). At present, only about 10% of European WWTPs produce biogas through anaerobic digestion. Although this technology allows energy recovery from organic waste, its wider implementation remains limited due to operational costs and the complexity of treating associated streams such as digestate, as well as the need to remove contaminants from biogas, particularly hydrogen sulfide (H₂S).

The LIFE GreenCouple project proposes an innovative solution based on coupling two complementary biotechnologies that simultaneously improve digestate management and biogas purification. The main objective is to develop an efficient, low-cost system with reduced environmental impact that facilitates the adoption of circular economy models in wastewater treatment, transforming treatment plants into infrastructures capable of producing renewable energy and recovering resources.

• A circular approach based on the integration of biotechnologies

The LIFE GreenCouple strategy is based on the integration of two biological processes that operate in synergy. On one hand, the system includes the use of constructed wetlands (CW), which represent nature-based solutions used to treat the liquid fraction of digestate generated during anaerobic digestion. Through this process, nutrients and emerging contaminants are removed while generating an effluent enriched in biogenic nitrates.

These wetlands are sequentially integrated with a suspended biomass bioreactor (SBB). The reactor receives the nitrified effluent produced by the wetland, which is used as an electron acceptor in an anoxic system that enables the biological removal of hydrogen sulfide present in the biogas. This process replaces conventional purification methods based on chemical reagents or activated carbon, significantly reducing chemical consumption and operational costs.

The combination of these two technologies makes it possible to simultaneously address two operational challenges in WWTPs: digestate treatment and biogas purification. As a result, biogas quality is improved, emissions associated with treatment processes are reduced, and energy recovery from the system is optimized.

• Pilot-scale validation

The system developed within LIFE GreenCouple will be scaled up and validated in three pilot plants located in Spain and Ireland. These facilities will allow the evaluation of system performance under real operational conditions, as well as its technical, environmental, and economic feasibility.

In addition to technological assessment, the project will incorporate advanced environmental evaluation tools, including life cycle assessment (LCA) and the quantification of greenhouse gas (GEH) emissions associated with the different processes. These analyses will help determine the potential reduction of environmental impacts and support the future transfer of the technology to the market.

• Contribution of the Limnology Group Grup (ICBiBE, Universitat de València)

The Limnology Group of the Institut Cavanilles de Biodiversity and Evolutionary Biology (ICBiBE) at the Universitat de València participates in the project by contributing its expertise in microbial ecology and biogeochemical processes in aquatic ecosystems and wetlands.

Within the LIFE GreenCouple framework, the group focuses on analysing the microbiological processes that sustain the functioning of the integrated system. The main research lines within the project include:

• Characterization of microbial communities involved in nitrification and biological desulfurization processes.
• Analysis of the taxonomic and functional diversity of bacteria and archaea using molecular biology and metagenomic tools.
• Evaluation of greenhouse gas (GHG) emissions associated with digestate treatment and the operation of the integrated system.
• Integration of these results to understand how the structure and dynamics of microbial communities influence system efficiency and environmental performance.

This approach not only contributes to optimizing system performance but also advances fundamental knowledge of the microbial processes regulating nutrient and gas cycling in nature-based solutions.

• Towards more sustainable wastewater treatment

The LIFE GreenCouple project is aligned with European policies aimed at improving energy efficiency, reducing emissions, and promoting circular economy approaches within the water cycle. It contributes to the objectives established in the recent revision of the Urban Wastewater Treatment Directive, which promotes the reduction of sectoral emissions and the transition towards energy-neutral wastewater treatment plants.

By integrating nature-based solutions with advanced microbial biotechnologies, LIFE GreenCouple aims to demonstrate that more sustainable, resilient, and efficient wastewater treatment models can be developed, contributing to the transition towards next-generation environmental infrastructures.

Reference: LIFE24-ENV-ES-LIFE-GreenCouple / 101214610
Total Budget: €2.512.001
EU Contribution: €1.507.200
Duration: 1 October 2025 – 30 September 2029
Programme: LIFE Programme

Lead Coordinator: Global Omnium Medioambiente S.L. Project Partners: Empresa General Valenciana del Agua S.A. (EGEVASA); Universitat de València (UVEG); RINA Consulting S.p.A. (RINA-C); BIA Energy Limited (BIAE); Danmarks Tekniske Universitet (DTU)

Principal Investigator at Universitat de València: Antonio Camacho

LIFE GreenCouple has received funding from the LIFE Programme of the European Commission under contract number 101214610. Views and opinions expressed are those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them.