Page 285 - Materials Chemistry, Second Edition

276 D. Rathore et al.

coproduct use changed the whole results of the study. Liska and Cassman (2008)
revealed that the prediction of emerging biofuel system’s performance can pose
additional challenges for LCA due to insufficient data of commercial-scale feed-
stock production and conversion systems. LCA of biofuel systems is currently
depending on laboratory- or pilot-scale data. Extrapolation of these laboratory-/
pilot-scale results to commercial-scale deployment must be made with caution
because of multiple unknowns that introduce significant uncertainty in the esti-
mation of life cycle energy efficiencies and GHG emissions (Liska and Cassman
2008). Standardized LCA methods and agreement on the most relevant metrics for
assessing different biofuel systems are essential to forge a consensus in the sci-
entific community, industrialist, and local people. That would help advance public
policy initiatives to encourage development of commercial-scale biofuel
industries.
There are two issues with regard to standardization. The first is choosing the
appropriate metric for the goal of the assessment, and the second is the appropriate
analysis framework to support the selected metric. Standardization procedure for
regulatory LCA metrics for GHG and energy balances of biofuel systems is
summarized by Liska and Cassman (2008) and presented in Table 2. The LCA
quantifies the potential benefits and environmental impacts of biofuels but existing
methods limit direct comparison of different processes within the biofuel pro-
duction system and between different biofuel production systems due to incon-
sistencies in performance metrics, system boundaries, and available data.
Therefore, the standardization of LCA methods, metrics, and tools are critically
needed to evaluate biofuel production systems for estimating the net GHG miti-
gation of an individual biofuel production system.

Table 2 Standardization procedure for regulatory LCA metrics for GHG and energy balances of
biofuel systems (adapted from Liska and Cassman 2008)
LCA element Standardization procedure
Biofuel system boundaries Explicit definition of system components and metrics for each
component and the entire system
Input parameters Evaluate variability, justify which are considered constant or
variable, use most recent and directly measured values where
possible
Crop production system Most appropriate county, state, or regional data depending on the
most appropriate scale and data availability for the biorefinery
facility under evaluation
Coproduct credits Based on representative coproduct use for the facility
Soil carbon emissions Based on measured changes in soil, if not available, an estimated
balance by appropriate ecosystem models
Nitrous oxide emissions Based on measured emissions, if not available, use estimated by
IPCC guidelines
Land-use change indirect Estimated using an appropriate global econometric model
GHG emissions depending on accepted national or international standards for
allocating these effects