Methodology

An open and consultative process on measurement standards is imperative on the road to a California carbon label, both to limit the cost and complexity to producers and to provide a meaningful environmental metric for consumers.

The methodological and technical challenges of measuring the greenhouse gas content are already being addressed by researchers both here, in California, and across the globe. Converting these measurement methods into a viable, practical carbon label involves crafting a compromise solution that is both accurate and precise, as well as feasible to implement for producers.

We envision a cradle-to-market methodology that relies on readily available industry-wide secondary data for many inputs to the production process and company-specific primary data for the California-based portions of the manufacturing process.


To date, most carbon labeling efforts have focused on process life-cycle assessments (LCAs) that rely on extensive investigations of supply chain carbon emissions. While these methods represent the most rigorous science, they are costly and time consuming and will prevent rapid and widespread adoption. A contrasting method uses national level economic and environmental impact tables to perform Environmental Input-Output LCAs (EIO-LCAs) to help consumers and companies estimate the amount of carbon embedded in consumer products. This method relies on national averages and does not incorporate company specific processes or practices. As such, it is less costly and time-consuming for businesses to implement, but does not allow the consumer to choose between two competing products on the basis of their carbon content.

A hybrid LCA combines the practicality of EIO-LCAs and the specificity of process LCAs by relying on company measurements of energy use and national averages of embedded carbon for purchased inputs. Companies can utilize information they already track – energy bills, purchased materials, and number of goods produced – to develop the information contained in a label. To the extent that manufacturers believe that their suppliers are less carbon intensive than the national average, documentation can be developed, and this information can be substituted for the national average data in the carbon content calculation.