Treatment conditions of the target feedstocks (paper sludge, olive pomace, orange peels) were optimized at lab and pilot scale. Continuous, long-duration pilot testing was conducted on-location where the residues were generated. The hydrothermally-treated residues were dewatered at pilot-scale on site using a mechanical filter press. The solids were dried and pelletized and the liquid fraction was tested for biogas production potential via anaerobic digestion. The pellets were characterized and compared to wood pellets and industrial pellets. Pellets produced in F-CUBED were pyrolyzed to produce a char and syngas.
Extensive modeling was performed based on the results of the lab- and pilot-scale tests, to develop a process model, reactor model, value chain model and to evaluate the techno-economic, environmental and social performance of the F-CUBED process.
Results show that the F-CUBED process is successful for treating the target residue streams, resulting in an energy yield > 50%, volume reduction > 83 %, and moisture removal Pellet quality for orange peel and olive pomace meets requirements for industrial-use pellets. Pellets produced from paper sludge were of lower quality, but were suitable for use in paper mills for heat generation. Pellets could be pyrolyzed consistently and resulted in good char conversion and syngas production (in particular olive pomace, although residual oil resulted in a less durable pellet).
The F-CUBED process demonstrated parallel recovery of oils (terpenes and olive oil). Nutrients (N, P) could be most successfully recovered from paper sludge processing. Solids from paper sludge processing could also be used as a partial coal replacement (4%) in briquette making for metallurgical applications.
The environmental performance of the F-CUBED process was excellent, demonstrating greenhouse gas emissions savings of 93%, 274% and 476% for paper sludge, olive pomace and orange peels, respectively, when compared to a reference case process for electricity generation from the residues. From a techno-economic and value chain perspective, the F-CUBED process is more energy efficient than reference processes. The best financial case is for the treatment of paper sludge. Value chain modeling further demonstrated additional cost savings via processing hubs.
Several dissemination activities were conducted to increase the visibility of the project for both the scientific and industrial communities. This includes 12 videos about the project (plus 10+ videos from the final conference), and over 30 articles and publications (peer-reviewed and industry-focused). Additional scientific publications will be published after the end of the project. Through the results and dissemination activities, the potential of the F-CUBED project and process has been showcased.
