## 5 Conclusions  
The benefits of the SustainSIM application are not only quantifiable but also highly practical, helping companies closely monitor how individual manufacturing activities influence overall CO2 emissions. This contributes to long-term carbon accounting improvements and the identification of the most effective sources of emission reductions. Thanks to interactive visualization, managers can track in real time how green technologies (e.g., solar panels, electric vehicles, and heat pumps) impact emission values, supporting them in strategic decision-making regarding production process optimization. The model provides in-depth analysis, which helps reduce energy costs and improve operational efficiency by enabling better planning and quicker adaptation to changing market and environmental conditions. Compliance with international standards and regulations, along with the ability to integrate with existing databases and systems, enhances the company's competitive position on the global market. In comparison with current methods, it has been confirmed that the application reduces analysis time to one-tenth of that required by LCA software, allowing companies to make data-driven decisions even before committing capital. A pilot deployment at VOMAS, Ltd. confirmed the potential for a 30% reduction in Scopes 1/2 with reasonable investment and indicated that SustainSIM can serve as the \"missing link\" between strategic ESG objectives and everyday production management. By extending traditional emission calculators with a digital twin in Unity, SustainSIM represents innovative and practically inimitable software, all within a single user interface. The SustainSIM application can therefore serve as a valuable tool for engineering companies focused on sustainable production process optimization and committed to continuous improvement in sustainability efforts. The objective of this publication was to present the development of a universal simulation application for emissions in engineering production. Based on the results of this work, we can conclude that the objective was met, as the model was successfully applied to a specific production process in an engineering company, and the obtained results aligned with expectations. The SustainSIM application also includes a data analysis tool, allowing for the comparison of different green technologies. The resulting data clearly demonstrate their impact on reducing the carbon footprint of the production process. However, the model still offers room for improvement, as many data points had to be extracted from activity records through manual calculations. In the future, these data could be automatically processed by the software, ensuring a seamless and user-friendly experience for companies optimizing and monitoring the carbon footprint of manufacturing processes. Further generative functions could be implemented, such as automated generation of production halls, integration with emission databases, and Scope 3 emission simulation. However, these additions exceed the current development scope, as the application remains under development. Therefore, further development is aimed at automatic integration with ERP, IoT, and expansion to Scope 3. It also includes the addition of financial indicators (NPV, IRR) directly within the simulation interface. This will make the application an even more effective tool for industrial sustainability. It can be concluded that a universally applicable digital reference and simulation model has been successfully created. The implementation of such a model could help executives and managers make more sustainable decisions. Further development of the application could expand its capabilities beyond emissions analysis to include economic evaluations of green projects and their associated emissions, significantly increasing the overall value of the universal digital reference model. **Author Contributions:** Conceptualization: J.K., J.S. and P.M.; methodology: J.S. ; software: R.S. and E.V. ; validation: P.M. and J.K.; formal analysis: E.V.