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Journal article explores hybridized life cycle analysis method

By Kris Bevill | April 04, 2012

A recently published article in the peer-reviewed Journal of the Royal Society Interface suggests that in order for life cycle analyses (LCA) of biomass-based products such as biofuels to be most accurately calculated, modelers should develop a hybridized methodology that considers both direct and indirect effects, to measure the carbon intensity of production. Further, the authors of the paper stressed the need for policymakers worldwide to develop methodologies that are compatible and comparable, rather than continue forward with the patchwork of individualized policies specific to country or region.

Susan Tarka Sanchez served as lead author of the paper, titled “Accounting for Indirect Land Use Change in the Life Cycle Assessment of Biofuel Supply Chains,” while working as the senior scientist at California-based business and environmental consulting firm Life Cycle Associates LLC, the company which developed the CA-GREET life cycle analyses model used by the California Air Resources Board in developing the state’s low carbon fuel standard.

Sanchez admits that indirect land use change (ILUC) continues to be a controversial topic, but said the group of international experts that contributed to the journal paper feel it is essential to incorporate indirect effects into biofuels methodology in order to gauge the full effects of the product. “It’s important to incorporate the uncertainty; to look at both ACLA [attributional life cycle analysis] and CLCA [consequential life cycle analysis] estimates separately, and as a combined system,” she said. “It’s better to not just look at one or the other. It is therefore important to hybridize the approaches and do a balancing of the two. Through this approach, standardizing the accounting frameworks can move forward.”

The worldwide standardization of frameworks garnered special emphasis in the group’s paper because they expect the impacts of biomass utilization to only increase on a global scale over time. “It’s not just about biofuels anymore,” Sanchez said. “Biomass is going into heat and electricity and chemicals, and food commodities are all mixed in. It’s a very fungible resource.”

Before determining that a hybridized LCA methodology would be an improved approach to biofuels life cycle assessments, the group first compared the direct, or attributional, LCA approach with the indirect approach. ACLA, according to the paper, provides information related to the direct emissions from products and therefore measures environmental flows to and from a system and its subsystems. Meanwhile, the CLCA measures physical and causal changes of those environmental flows in response to global economic signals that may be indirectly associated with fuel use. In short, ACLA calculates emissions directly related to the production of a certain product while CLCA accounts for the overall emissions levels associated with that product’s production. Each approach offers valuable information related to emissions sources and levels. Therefore, the group determined that by updating the models and combining their capabilities, the resulting hybridized approach could more effectively advise policymakers as to the results of implementing biofuels and other biomass-focused policies.

Policymaking bodies including the U.S. EPA and CARB already incorporate aspects of both approaches into their biofuels policies, but the policies have been developed separately and in such a way that it can be difficult to determine what methodologies were used to reach the end numbers. The European Commission has taken yet another approach to the subject, setting some limitations for biofuels production on certain types of land while continuing to evaluate various ILUC models. Third world countries have largely been left out of the development process. Therefore, the group urged for the establishment of comparable and compatible ILUC policies between all biofuel producing countries. “To move towards standardization, you need to be able to harmonize the models and be able to explain the approaches, and differences, in laymen’s’ terms,” Sanchez said. “It’s hard when a biofuel developer looks at a number that comes out of a model approach that, if you did not really understand the combined model approach, you can’t trace it back. That’s really very important.”

It is uncertain when a global standard for full LCA can be agreed upon, but Sanchez and the paper’s fellow authors, which included researchers from Shell Oil, the University of California-Berkeley, the European Commission’s Joint Research Center renewable energies unit, and others, concluded that immediate focus could be placed on mitigating the risk of ILUC. Recommended measures included additional agricultural research and development to increase yields of both energy and food crops, protecting high carbon-stock land and degraded lands, and determining best agronomic practices and encouraging the use of those methods.