Globally, there is a growing focus and emphasis on the conversion of carbon emissions. In the context of dual carbon goals, carbon emission management has become a crucial method for energy conservation, consumption reduction, and technological transformation. However, existing carbon accounting methods tend to be biased towards scientific theoretical research, lacking a practical methodology for calculating the carbon dioxide equivalent. Therefore, this paper proposes a novel method for the environmental engineering investment, construction, and operational carbon conversion process. This method encompasses a full process, full coverage, and full correlation, while being easy to operate. It involves collecting data during the operational phase of a project and converting this data into carbon emission quantities. This allows for the calculation of the carbon conversion value of economic indicators and the total carbon emissions. Particularly, the approach of simulating the carbon conversion value of economic indicators and incorporating it into the total carbon emissions of the environmental engineering investment, construction, and operational process offers a valuable research path for the holistic assessment of environmental engineering projects and related scientific studies.