More caution is needed when using life cycle assessment to determine energy return on investment (EROI)

Abstract

KeywordsPrimary energy; Cumulative energy demand; LCA. Highlights• LCA can be used to determine EROI, but misclassification of energy flows can occur • Supply chain losses included in LCA need to be adjusted for when determining EROI • Inconsistencies in heating value assumptions in LCA databases have misled analysts • Differential weighting of primary energy forms in LCA-EROI should be reconsidered AbstractCumulative energy demand (CED) estimates from life cycle assessments (LCAs) are increasingly used to determine energy return on investment (EROI), but the difference in indicators can lead to a misclassification of energy flows in the assessment. The core idea of EROI is to measure the relation of energy diverted from society to make energy available to society. CED, on the other hand, includes forms of energy that are not appropriated by society, such as fugitive methane emissions from oil wells as well as losses of heating value of coal during transport and storage. Such energy forms should be excluded from EROI; failure to do so leads to results that are inconsistent with the intention of EROI and potentially misleading. We demonstrate how this problem is at least partially rectifiable by adopting consistent energy accounting, but also note that among the energy flows not appropriated by society occurring in CED, not all flows can easily be removed. Further, we point to inconsistencies in heating value assumptions in a widely used database that have misled analysts. Finally, we argue that the differential weighting of primary energy forms in published CED-based EROI work is unsubstantiated and should be reconsidered.

Comparing World Economic and Net Energy Metrics, Part 1: Single Technology and Commodity Perspective

“…This quantity is not the same as "cumulative energy demand" as calculated in many life cycle assessments that include the full energy content of feedstocks (as discussed in [49]). As discussed in King [29], Equations (7) and (8) count feedstock energy input only as that energy that is dissipated as heat by the technology being modeled (e.g., energy leaving a power plant originated in the feedstock, but was not dissipated within the plant boundary) [29].…”

Developing an Input-Output Based Method to Estimate a National-Level Energy Return on Investment (EROI)

“…As data collection can be problematic and time consuming when undertaking process analysis "from scratch", established LCA data sets are sometimes used (see for example Harmsen et al [40]). Although, as Arvesen and Hertwich [41] note, care is needed to ensure that LCA boundary conditions are consistent with the EROI calculation.…”

Comparing Apples to Apples: Why the Net Energy Analysis Community Needs to Adopt the Life-Cycle Analysis Framework

“…However, within the field of life cycle assessment (LCA) standards from the International Organization for Standardization ( [15][16][17][18][19]) have provided a way to mesh the two that has allowed for meaningful research over the past two decades. The developments within the field of LCA are now being applied to NEA [7,10,20,21], and seem to be finally reconciling the issues that first arose in the 1970s. The goal of this paper is to discuss how the methodologies of NEA are related to the ISO LCA standards and how it would make more sense to view NEA as a Even when studies use the same unit of comparison the final results can still vary widely due to methodological differences.…”