# Urban Biorefinery Demonstration: Production of Polyhydroxyalkanoates from a Municipal Solid Waste
## 5 Conclusions  
This study successfully demonstrates the feasibility of scaling up scl-PHA production from the OFMSW, validating the bioprocess under real operational conditions. The results confirm that the conversion of OFMSW into VFAs and their subsequent utilization as a carbon source for PHA synthesis is not only technically viable but also aligns with the principles of circular economy and sustainable waste valorization. The industrial-scale implementation of the bioprocess presented shows significant potential to reduce dependency on fossil-based plastics while contributing to waste management strategies. The production of 83 kg of scl-PHA over 29 accumulation batches demonstrates the robustness of the bioprocess, with promising yields comparable to those obtained at earlier stages of the technology readiness level. The scl-PHA has been produced from 23.5 t of VFA-rich digestate. It can be concluded that not controlling pH did not promote a detrimental effect on the production of PHAs, but low environmental temperatures did cause a destabilization in the enrichment fermenter during the winter season, although it was followed by an MMC adaption. Good aeration and agitation strategies are essential to obtain high percentages of PHAs during the accumulation step. Thus, DO concentration must be ensured to be over 70% to reach high rates of scl-PHA accumulated by microorganisms. The COD feeding rate during the accumulation reaction could be increased up to four times the COD consumption rate of the enrichment reaction, by reaching up to 58 wt.% of PHA in the MMC cells. In addition, most of the organic matter was used for MMC growing at the PHA accumulation phase. Moreover, the high extraction efficiency (92%) and purity (90%) achieved highlight the effectiveness of the solvent-based recovery method at demonstrative scale. However, for full-scale industrial deployment, the economic viability of the process must be further assessed. Key factors such as process optimization, energy consumption, solvent recovery, and market competitiveness must be carefully analyzed to ensure the financial sustainability of PHA production. The cost-effectiveness of aeration, substrate feeding strategies, and downstream processing, particularly in solvent extraction, will be critical in determining the commercial feasibility of this technology. Additionally, exploring the scalability of different feeding rates and substrate compositions will be essential to maximize PHA storage efficiency while maintaining process stability. In summary, this work represents a significant step towards the industrialization of scl-PHA production from municipal waste streams. While technical feasibility has been demonstrated, further advancements in process efficiency, cost reduction, and sustainability assessments will be necessary to establish PHA bioplastics as a competitive alternative to conventional plastics. Conceptualization, I.I. ; Methodology, I.I., I.A. and F.J.P. ; Formal analysis, I.I. and I.A. ; Investigation, I.I., I.A., F.J.P. and J.M. ; Data curation, I.I. ; Writing--original draft, I.I. ; Writing--review & editing, F.J.P. and J.M. ; Supervision, F.J.P. and J.M. ; Project administration, J.M. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by Bio-Based Industries Joint Undertaking through the project URIBOFIN (Grant Agreement Number 745785). And The APC was funded by IRIAF (Regional Institute for Agri-Food and Forestry Research and Development of Castilla-La Mancha). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Data is contained within the article. **Acknowledgments:** The authors would like to acknowledge to URBASER (Zaragoza, Spain) for providing the OFMSW digestate and to AINIA (Valencia, Spain) for the scientific advice.