Hybrid Path Methodology

Scope 3 GHG accounting is riddled with methodological inconsistencies, often producing vastly different results across companies with similar value chains. This lack of comparability undermines efforts by investors, sourcing managers, and other stakeholders to effectively assess and mitigate climate-related risks. Spend-based approaches using EEIO inventories are particularly criticized for relying on broad, supplier-agnostic average data, leading to the common (and flawed) conclusion that “the only way to reduce emissions is to spend less.” But the issue isn’t with spend itself—it’s with the use of oversimplified, highly aggregated emissions factors. Comparing averages to other averages yields only more averages—and little actionable insight.

TASA’s Hybrid-Path addresses this by starting with disaggregated emissions structures generated by TASA-EFX rLCA models. These structures map more than 130,000 nodes where emissions occur, including the upstream input flows behind each node. Hybrid-Path enables you to replace generalized averages with supplier and process-specific data, allowing you to quantify the impact of not just spending less, but spending smarter—targeting interventions where they matter most.

Thanks to the unique structure of monetary Leontief input-output systems—and the theoretical equivalence of input-output, process-based, and activity-based node-path structures—it is possible to establish concordance across inventory approaches. This enables the substitution of aggregated, top-down input-output data with more precise bottom-up process data and company-reported values.

Hybrid-Path leverages this equivalence to assess specific products, capturing differences in technologies and processes across unique supply chains, while preserving the system boundary completeness of the EEIO approach. Hybrid-Path minimizes double-counting, avoids systemic disturbances, and reduces reliance on external data—making it a scalable, transparent, and adaptable method for superior Scope 3 carbon accounting.

TASA scientists—alongside leading researchers around the world, have contributed extensively to the development of hybrid and streamlined life cycle assessment (LCA) methods. Until recently, however, these approaches have largely remained theoretical, confined to academic literature. Hybrid-Path brings them into practical, everyday use.

Hybrid-Path delivers actionable insights into both the total emissions and the structural composition of emissions across comparable products and activity systems. In contrast, most conventional Scope 3 accounting relies on a single EEIO model (e.g., the U.S. EPA EEIO model, EXIOBASE, or Defra) to assign emissions factors to purchased goods, services, or capital inputs. This means products made under very different technological and organizational conditions are often represented by the same average industry category—resulting in identical footprints and reinforcing the flawed logic that emissions can only be reduced by spending less.

Hybrid-Path overcomes this limitation by generating increasingly comparable estimates of both emissions intensity and structure. Through customizable nodes and paths, it integrates unique foreground data—covering specific processes, facilities, technologies, and organizational practices—into the broader emissions system. These digital twins of supply chains not only replicate the current emissions embedded in a product or service, but also quantify the impact of potential changes, such as adopting new technologies or process improvements.