Building Science for Environmental Protection in the 21st Century - Science For Environmental Protection: The Road Ahead - page 122

based LCA is a bottom-up approach that involves itemization of each step in
producing a product and consideration of everything from extraction through
production and disposal. Although informative and readily interpretable, it sys-
tematically underestimates environmental effects by missing key secondary and
“ripple” effects (Majeau-Bettez et al. 2011). Data are often inadequate, and
strategies to figure out the best way of drawing system boundaries need atten-
tion. In addition, although the life-cycle inventory can be constructed in many
situations, determining the health or ecologic effects can be challenging given
the array of pollutants, the broad scope, and the resulting lack of site specificity
of emissions or effects. Researchers have developed approaches to integrating
health risk-assessment concepts into process-based LCA, taking account of such
factors as pollutant partition coefficients, stack height, and population density to
refine the characterization of effects (Humbert et al. 2011), but more work
clearly is needed. The second approach involves conducting input-output LCA,
in which large matrices of transfers between economic sectors are constructed.
That allows consideration of the full ripple effects of actions that are influencing
a specific sector (Majeau-Bettez et al. 2011) but with even greater challenges in
linking outputs of economic-sector activity with defined health and environ-
mental effects.
EPA has some internal capacity in LCA, has been required to conduct
LCA of fuels in the Energy Independence and Security Act of 2007, and has
developed tools such as the Tool for Reduction and Assessment of Chemical and
Other Environmental Impacts (Bare 2011); but LCA has not been systematically
applied to the agency's mission. LCA tools and inventories have been much
further developed and applied in other regions, such as Europe (Finnveden et al.
2009). Nonetheless, even without undertaking a formal quantitative LCA, com-
plex systems-level challenges require that the agency at least apply “life-cycle
BOX 4-3 The Need for and Challenges of
Life-Cycle Assessment: The Biofuels Case
The need for and challenges of LCA are seen in the case of biofuels.
Some analyses suggest that regulatory requirements regarding the use of
such fuels may not reduce carbon dioxide emissions and indeed might even
increase them (NRC 2010). Those analyses suggest that such mandates
could result in a loss of US crop lands available for food production because
of the use of the land to produce fuel. That, in turn, could result in pressures
to clear forest land in other parts of the world (which is an example of indirect
land-use effects) (Searchinger et al. 2008). In addition, the fertilizer to grow
such fuel crops in the midwestern United States may contribute to runoff that
exacerbates the anoxic zone in the Gulf of Mexico (Rabalais 2010). Thought-
ful analysis and interpretation of the results of LCA for biofuels are necessary
because some of its methods and assumptions remain controversial (Khosla
2008; Kline and Dale 2008).