1. Definition of product life cycle assessment
Life Cycle Assessment: Life Cycle Assessment (LCA) is a quantitative evaluation method. It covers the entire life cycle of a product – from natural resource extraction to raw material processing, product manufacturing, distribution, use, and finally disposal or recycling.
LCA quantitatively calculates and evaluates the resources and energy consumed by products, as well as the environmental load of emissions, and usually evaluates a variety of environmental impact types, including resources, climate change, atmospheric environment, water and soil toxicity, etc., among which LCA is particularly common for enterprises to calculate product carbon footprints.
2. Product life cycle assessment process
The ISO (International Organization for Standardization) 14040 series defines the basic framework for LCA. According to the ISO standard, LCA evaluation consists of four stages: definition of objectives and scope, analysis of life cycle inventory, life cycle impact assessment, and life cycle interpretation.
1、目标与范围定义（Goal and Scope Definition）
(1) Definition of objectives: First, it is necessary to clarify why LCA is being conducted and how the results will be used. This may include, for example, improving product design, supporting marketing claims, guiding policy development, or providing consumer information. The target definition should also indicate which stakeholders are reporting and their information needs.
(2) Functional unit: A measure around which all data collection and impact assessment is carried out, e.g. "per kilogram of product".
(3) System boundaries: Determine which life cycle phases (raw material collection, production, transportation, use, disposal, etc.) will be taken into account and which processes will be excluded.
There are usually two ways to choose a system boundary, either cradle to gate, or cradle to grave, the former for intermediate products such as electrolytic aluminum, plastics, and the latter for end products such as cars, mobile phones, furniture, etc.
(Figure 1 Selecting a system boundary)
(4) Data quality requirements: set the time range, geographical scope, technical representativeness and accuracy of the required data.
Ø Time span: the time span between the data year and the collected data.
Ø Geographical scope: the region where the unit process data is collected.
Ø Technology coverage: specific technology or combination of technologies.
Ø Precision: A measure of the change in each data value (e.g., variance).
Ø Completeness: the proportion of measured data or background data.
Ø Representativeness: The dataset reflects the qualitative evaluation of the actual interest group.
Ø Consistency: whether the research method can be uniformly applied to the qualitative evaluation of different analysis contents.
Ø Reproducibility: a qualitative evaluation of the likelihood that other independent personnel will use the same methodology and data to obtain the same results.
Ø Uncertainty in information (e.g. data, models and assumptions).
(5) Assumptions and Limitations: Document any necessary assumptions and potential constraints that may affect the interpretation and communication of results.
(6) Impact category selection: Determine which environmental impact categories will be included in the assessment, such as global warming potential, ozone layer depletion potential, acidification potential, etc
2、生命周期清单分析（Life Cycle Inventory Analysis，即LCI）
After defining the objectives and scope, the next step is a Life Cycle Inventory analysis, which aims to quantify the inputs and outputs associated with the product system. Unit process dataset acquisition generally includes six data types:
(1) Products and by-products of the unit process (valuable outputs include non-physical outputs, i.e., services).
(2) Consumption of natural resources in the unit process (coal, oil, natural gas, forests, groundwater, etc., without traceability).
(3) Consumption data of raw and auxiliary materials and other materials (tap water, reclaimed water, etc. that have been manually processed should not only know their consumption, but also continue to trace back to natural resources in principle).
(4) Energy consumption data (secondary energy).
(5) Environmental emissions (including greenhouse gas emissions, which are directly discharged into the natural environment, only need to know the quantity, no need to trace).
(6) Waste to be disposed of (wastewater, waste, hazardous waste, etc., in principle, the disposal process should be traced backwards).
Once the data type is defined, a life cycle model is established, after which the data is collected and associated with unit processes and functional units. By calculating and summarizing this data, the inventory results of the product life cycle are derived, and the following figure is the basic step of the life cycle inventory analysis.
3、生命周期影响评价（Life Cycle Impact Assessment，即LCIA）
Life Cycle Impact Assessment (LCIA) is the third stage of a Product Life Cycle Assessment (LCA). The goal is to interpret and evaluate the data collected in the previous phase (Life Cycle Inventory Analysis, LCI) to understand the potential environmental impact of a product or service from cradle to grave. LCIA attempts to quantify the impact of factors such as greenhouse gas emissions, resource consumption, and the release of toxic substances on the environment and human health (greenhouse gas emissions are used as an example in this article). The LCIA methodology process typically includes the following steps:
(1) Select the impact category and category indicators: In this step, the researcher needs to determine the environmental impact category to be evaluated, such as global warming potential (GWP), ozone depletion potential (ODP), acidification potential (AP), eutrophication potential (EP), etc. Each impact category has a corresponding category metric that measures the severity of a particular environmental problem.
(2) Classification: The input and output data identified in the LCI stage are classified into different impact categories according to their possible environmental impacts.
(iii) Characterization: In this step, various emissions and resource consumption are converted into common units of measurement under the corresponding impact categories by using specific models and category metrics. For example, carbon dioxide, methane, and other greenhouse gases can be converted into carbon dioxide equivalents to measure their contribution to global warming.
(iv) Normalization: Normalization is an optional step designed to provide a reference point against which results can be compared across different impact categories. The impact of each category is usually compared to the total annual impact of a region, such as Europe or the world.
(5) Weighting: Weighting is also an optional step to reflect the relative importance of different environmental impacts. This step involves subjective judgment and is influenced by culture, policy, and personal values.
(6) Interpretation: Based on the collected and analyzed data, draw conclusions and provide recommendations.
4、生命周期解释（Life Cycle Interpretation）
LCA is the final stage of Life Cycle Assessment (LCA) and aims to analyze and interpret the results obtained in the previous phases. This phase involves identifying significant environmental issues, assessing the integrity and reliability of the data, understanding the uncertainties of the results, and making recommendations based on the findings. Life cycle interpretation enables decision-makers to make more informed choices based on the results of LCAs and guides future actions.
LCA methodology process
(1) Summary of results: Summarize the data and results of the Life Cycle Inventory (LCI) and Life Cycle Impact Assessment (LCIA) phases.
(2) Key Problem Identification: Identify and focus on those factors or processes that have the greatest impact on the overall research results.
(3) Consistency check: Verify whether the various steps of the LCA are consistent, including the definition of objectives and scope, the selection of methodology, and the quality of data.
(4) Sensitivity analysis: Analyze how changes in input parameters affect the LCA results to assess the robustness of the conclusions.
(5) Uncertainty assessment: Evaluate the variability of results due to uncertainty in data, methodology, or model.
(6) Interpretation of results: Based on the above analysis, the LCA results are comprehensively interpreted to form meaningful conclusions and recommendations.
(7) Report preparation: Prepare detailed reports, record all important information and interpretation processes, and ensure transparency and reproducibility.
3. Application scenarios of life cycle assessment
(1) Product carbon accounting: The evaluation method of ICA is adopted, but ICA includes the evaluation of the impact on climate, energy, health, etc., while the product carbon footprint mainly focuses on the impact of evaluation on a single indicator of climate and environment, and refines the information on greenhouse gas emissions of products.
(2) Product design and improvement: Life cycle assessment can guide decision-making during the product design phase, optimizing material selection, production processes and packaging to reduce negative environmental impacts.
(3) Supply chain management: Assessing environmental hotspots in the entire supply chain can help enterprises choose environmentally friendly suppliers, reduce transportation costs, and reduce resource waste, thereby improving the sustainability of the overall supply chain.
(4) Environmental labeling and certification: Through the results of life cycle assessment, products can obtain environmental protection-related certifications, such as carbon footprint, environmental product declaration, etc., so as to gain a competitive advantage in the market.
(5) Policy formulation and compliance: It is used to adapt to the requirements of environmental protection policies and ensure the compliance of enterprises in environmental regulations and standards to reduce environmental impact.
(6) Enhance market competitiveness: disclose and communicate the environmental performance of products, meet consumers' needs for sustainable development, improve brand image, and enhance market competitiveness.
Fourth, summary
Life Cycle Assessment (LCA) is a comprehensive assessment of the environmental impact of a product, process or service throughout its life cycle. It plays a key role in product design, policy development, supply chain management, marketing, environmental assessment, waste management, energy, and agriculture, among others. Through the analysis of raw material acquisition, production, use and disposal, LCA helps decision-makers identify areas for improvement, promote efficient use of resources and environmental protection, and enhance the sustainability of companies and products.
Product carbon accounting, a key application area of Life Cycle Assessment (LCA), focuses on measuring the greenhouse gas emissions generated by products throughout the entire process from raw material acquisition, manufacturing, transportation, use and disposal. This process not only helps companies identify and reduce their carbon footprint, but also drives the design and innovation of low-carbon products, while meeting growing environmental regulations and consumer demand for sustainable goods. Through accurate carbon accounting, organizations can achieve more transparent environmental disclosures, improve market competitiveness, and promote the development of a green economy on a global scale.
For more information, please feel free to send us a private message: AMT Qiyuan Carbon Management Team.
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