The following text will consider all four calculation methods with respect to the datapoints identified in this project, starting with the “spend-based” method. This is the least precise calculation method, as seen in figure 9, in terms of estimating CO2e emissions for a product or service. Through the spend-based method, CO2e emissions are estimated by multiplying the product's price by an emission factor. In this regard, while prices can indicate the CO2e emissions - e.g., higher-priced products may have longer lifespans or eco-friendly materials – applying this method often provides a misleading picture. For instance, in cases where the same emission factor has been applied to both an older and a newer version of a product, despite price differences, it often shows the product with the higher price has greater CO2e emissions. Therefore, this method should only be used as a last resort when no other data is available. Supporting datapoints like “Product Type,” “Amount Ordered,” and “Unit of Measurement” can help improve accuracy by enabling access to more precise emission factors from external databases.
Regarding the Supplier-Specific calculation method, the most accurate and reliable approach, suppliers are required to provide specific CO2e figures for every purchase. The datapoints required for this method include "CO2e factor in kg per unit sold" and confirmation that the datapoint "CO2e source information" is set to "specific”. Yet, if the specific CO2 emission factors are not known, available or only account for some of the products’ life cycle, the reporting company can make use of the average data or hybrid calculation method. Using the average-data method, requires that the supplier has filled out the datapoints: “Unit of Measurement”, “Product Type” and “Material Origin”. This allows the reporting company to accurately identify the appropriate industry-average emission factor to calculate the CO2e emissions of the product.
Regarding the hybrid-method, it requires that the datapoints within the "Product Information" and "Product Measurement and Units" datapoint-groups are filled out. More specifically, the data needed is data such as mass, volume of the material used in the product, disposal, waste information etc. This enables the reporting company to identify appropriate secondary emission factors or fill out the gaps to calculate the full CO2e emissions of the acquired product.