As the development and research processes for the biofuel industry continue to increase, so does the necessity for accurate comparisons and appraisals of the fuels themselves. Although second-generation biofuels hold great promise as a supplemental energy supply, the ecological and environmental consequences cannot be fully understood without enhancing and standardizing the computational tool of “Life Cycle Analysis” (Davis et al 2009). Because the currently incomplete datasets can cause signiﬁcant variation in the estimates for both the energy yields and the greenhouse gasses (GHG) associated with biofuel production, increasing more inclusive ecological data and establishing uniform units of comparison are both key components of furthering the accuracy of comparable fuel analysis. — Elena Davert
Davis, S., Anderson-Teixeira, K., DeLucia, E. Life-cycle analysis and the ecology of biofuels. Trends in Plant Science 14 (3) (2009) 140-146.
Life Cycle Analysis, or LCA, is an all-inclusive account of the inputs and outputs of a production system, likened to an ecological food web that traces the fluxes of energy throughout an entire system. In the case biofuel production, some example inputs and outputs are energy requirements and net yields, economic costs and surpluses, and ecological feedstocks and environmental consequences. More specifically, the life-cycle inventory is a list of components assessed within an LCA for each step of the production chain; for biofuel LCA, the life-cycle inventory could include components such as manufacture and transport of fertilizers, pesticides, herbicides and seeds, to represent the inputs for step of feedstock production. However, not all life-cycle inventories include the same components even when the boundary for the analyzed system is same. The life-cycle inventory thereby inﬂuences the outcome of an LCA and can be manipulated in order to understand which components have the greatest effect on the calculation of GHG balances for various fuels. LCA results are also frequently used in political and economic applications such as cost-benefit analysis, so accurate and comprehensive scientific data is crucial to evaluating the ecological and economic sustainability of biofuel crops.
In the reported survey, the authors compared published biofuel studies that analyzed corn, switchgrass, miscanthus, and mixed temperate grasses using various methods LCA, and found a number of indicators that more specific ecological understanding should be incorporated into the analysis. For example, the net energy values (NEV) and fuel energy ratios (FER) had drastic ranges across all reports and species, highlighting the fact that many types of energy are not directly comparable because they inherently incur very different costs and beneﬁts. The authors also realized that even within reports regarding the same species, inconsistencies developed due to conflicting initial data. Not only did variation in life-cycle inventories produce discrepancies among the LCA reports, but only three studies included uncertainty estimates of inventory item values and many of the inventories were incomplete.
In addition, although topography, soil and climate variability within a region prevent the direct application of small-scale LCA data to larger areas, this was ignored in many of the reports and yielded inaccurate assessments. The authors also noted that many LCA analyses ignored the fact that fuel energy production is so closely inﬂuenced by economic and political interactions and failed to communicate in common terminology to the professionals (engineers, economists and policymakers) who work within other branches of the biofuel production system.
Second-generation biofuels have potential as alternate forms of energy, but the consequences of increasing the use of biofuels cannot be communicated without a transparent and standardized approach to LCA. By increasing collaboration among ecologists, economists and engineers, a more holistic approach to constructing the inventories will lead to more accurate appraisals of biofuel potential.