The concept of “carbon footprint” is derived from “ecological footprint”, which is mainly expressed in terms of CO2 equivalent (abbreviated as CO2eq), the total greenhouse gas emissions from human production and consumption activities. Compared with the single CO2 emission, the carbon footprint is a life cycle assessment method to evaluate the greenhouse gas emissions directly or indirectly generated by the research object during its life cycle, and for the same object, the accounting of carbon footprint is more difficult and broader than carbon emission, and its accounting result contains the information of carbon emission. The precise definition and understanding of “carbon footprint” is still evolving and improving, and different scholars or organizations have different focuses on the concept and connotation of “carbon footprint”, among which scholars define it more from the perspective of life cycle assessment, while organizations define it mainly according to The concept and meaning of “carbon footprint” are defined by different scholars or organizations, with scholars defining it more from the perspective of life cycle assessment and organizations defining it mainly according to the background and function of the evaluation target. At present, the carbon footprint can be divided into “national carbon footprint”, “urban carbon footprint”, “organizational carbon footprint”, “corporate carbon footprint”, “carbon footprint” and “carbon footprint” according to its application level (analysis scale). “corporate carbon footprint”, “household carbon footprint”, “product carbon footprint”, and “individual carbon footprint”.

Process life-cycle assessment (Process-based, PLCA), which is the most traditional method of life-cycle assessment, is still the most mainstream evaluation method (ISO, 199SETAC, 1993, 1998). According to the “Principles and Framework for Life Cycle Assessment” (ISO 14040) issued by ISO (ISO, 1998), the method consists of four basic steps: definition of objectives and scope, inventory analysis, impact evaluation and interpretation of results, and each basic step contains a series of specific step processes. The process life cycle assessment method uses a “bottom-up” model, based on inventory analysis, to obtain all the input and output data of a product or service during its life cycle through field monitoring and research or its other database information (secondary data) collection, to account for the total carbon emissions and Environmental impact. For micro-level (product or service-specific) carbon footprint calculation, the process life cycle approach is generally used.