The Rural BioReFarmeries (RBRF) project is rethinking how we can build local, circular and sustainable value chains for bio-based products. By focusing on small-scale and decentralised green biorefineries, the project aims to unlock the potential of rural areas across Europe — reducing waste, boosting local economies and supporting the EU’s green transition.
To successfully achieve the project’s mission, the 19 partners that conform the RBRF consortium are joining forces across 8 work packages. This article focuses on Work Package 4 (WP4), led by University of Galway.
WP4 in a nutshell
Title: Production of Fatty Acids, Biogas and Nutrients from Brown Juice
WP Leader: Vincent O’Flaherty, University of Galway
In biorefinery systems, side-streams that were once considered waste can become valuable raw materials. For example, the liquid fraction left after extracting proteins from grass, known as brown juice, is rich in organic compounds and nutrients that hold significant potential for bioconversion. In WP4, researchers are developing advanced microbial and separation processes to transform brown juice into volatile and medium-chain fatty acids, renewable biogas and recoverable nutrients. These outputs will serve as critical building blocks for bio-based products, energy generation and sustainable fertilisation strategies.
Key objectives
WP4 has three main goals:
- Produce and scale up the generation of volatile fatty acids (VFAs), medium-chain fatty acids (MCFAs), and biogas from brown juice residues.
- Develop methods to purify and recover fatty acids, making them suitable for use in downstream applications within WP5.
- Separate and test the nutrient-rich digestate produced in the process for reuse as a sustainable fertilizer on agricultural land.
Main tasks and technical activities
To meet these objectives, WP4 is carrying out a series of coordinated tasks:
- VFA and biogas production: Using two-phase anaerobic mixed culture fermentation, researchers first optimise processes at the lab scale and then upscale production for demonstration plants in Ireland and Denmark.
- MCFA production: Led by Poznań University of Technology, this task focuses on developing and scaling valuable MCFAs from brown juice, using chain elongation techniques.
- Purification and recovery of VFAs: Led by Trinity College Dublin, these tasks involve developing membrane, ion exchange, and hybrid purification processes to separate VFAs from dilute streams, and later recover specific VFAs for high-value products.
- Nutrient recovery: Investigating how nutrients left in post-digestion streams can be recovered and reused, closing the loop by returning them to agricultural soils.
A collaborative effort
This work package is a joint effort between leading European research institutions and universities, each bringing unique expertise. The team from O’Flaherty Lab, based at University of Galway, coordinates the production processes, while Poznań University of Technology leads the development of MCFA production; Trinity College Dublin also plays a central role in advancing purification and separation technologies.
The Irish and Danish demo sites, managed by Munster Technological University and Aarhus University respectively, will be involved across testing, optimisation and scaling-up processes.
This interdisciplinary approach ensures that WP4 covers the entire chain: from lab-scale innovation and pilot demonstrations, to purification, nutrient recycling and validation at scale.
Expected outcomes
WP4 will deliver a series of reports focused on:
- Comprehensive characterisation of brown juice and its potential as a feedstock for bio-based products.
- Optimisation and scale-up of VFA, MCFA and biogas production processes in Ireland and Denmark.
- Innovative purification and recovery processes for VFAs, making them suitable for high-value applications.
- Insights into nutrient recovery for sustainable reuse in agriculture.
By turning a low-value by-product into renewable energy, valuable fatty acids and nutrient-rich fertilizers, WP4 demonstrates the power of biorefineries to achieve true circularity. These innovations will not only reduce waste but also create new value streams for rural communities, supporting both environmental sustainability and rural competitiveness.