## 6 Concluding Remarks  
This study confirmed the high energy dependency of pet food production processes, with thermal energy accounting for 62.3% and electrical energy for 37.7% of the company's total energy demand. At the product level, this corresponds to approximately 1 GJ of thermal energy and 0.6 GJ of electrical energy per Mg of pet food produced. While the company benefits from a supply contract with the local electricity distributor for non-conventional renewable energy, its dependence on natural gas for thermal processes remains a significant obstacle to achieving carbon neutrality by 2050. Drying and extrusion were identified as the most energy-intensive processes, with the dryer accounting for 68.8% and the boiler for 30.9% of the natural gas used for steam generation.  
These two systems were also the main contributors to GHG emissions in proportion to their natural gas consumption. The production of one Mg of pet food results in 0.048 Mg of CO\({}_{2}\)eq emission, of which 68.8% is attributed to the dryer and 30.9% to the boiler. These findings underscore the need for targeted energy efficiency and mitigation strategies that specifically address these units.  
To further enhance sustainability, the study investigated the valorization of unsellable pet food waste as a biomass fuel. The material exhibited a high calorific value of 0.0195 GJ kg\({}^{-1}\), an ash content below 1%, and low levels of heavy metals, characteristics comparable to radiata pine wood. Combustion tests using TD-GC/MS indicated that emissions from dog food waste are not significant contributors to environmental odors. Corrosion studies revealed that the effect on boiler pipes was comparable to that of natural gas. Although cat food combustion proved to be approximately 30% more corrosive than. Overall, these findings support the feasibility of fueling industrial boilers with a biomass blend of unsellable pet food waste and wood chips, enabling the generation of thermal energy for extrusion with a carbon-neutral footprint. This strategy not only advances circular economy principles but also significantly reduces GHG emissions, aligning with the company's long-term commitment to achieving carbon neutrality by 2050.  
Conceptualization, D.H.; methodology, D.H. and J.A.-H.; validation, J.A.-H., F.d.G., F.A., and D.H.; formal analysis, J.G. and D.H.; investigation, J.A.-H., F.d.G., F.A., and D.H.; resources, J.G., H.Q.-L., and D.H.; writing--original draft preparation, J.D. and J.A.-H.; writing--review and editing, J.G. and H.Q.-L.; visualization, J.G. and H.Q.-L.; supervision, D.H. and H.P.-F.; project administration, H.Q.-L. and D.H.; funding acquisition, H.Q.-L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
**Acknowledgments:** [PERSON], [PERSON], and H.Q.-L. acknowledge funding from the National Fund for Scientific and Technological Development (FONDECYT), Chile, under Grant Nos. 1240819, 11250144, and 1240765. The authors also acknowledge the support from the Centro Tecnologico de Conversion de Energia (CTCE), Universidad de Talca.  
**Conflicts of Interest:** The authors declare no conflicts of interest.