(393b) Complexity Analysis of Gasoline and Corn-Ethanol Life Cycle Networks

The decision of using corn-ethanol vs gasoline requires consideration of a variety of factors., and life cycle analysis techniques have been applied to understand the tradeoffs between these two fuel options. Metrics like global warming potential, energy return on investment, resource consumption, water footprint etc. are some of the common metrics that have been used to study the impact of these two fuel choices. [1] However, an interesting feature can be revealed about the use of two fuels when the life cycle network of these fuels is studied using network analysis methods such as cycling, resilience, ascendancy or structural path analysis. In this work, the cycling index of material use over the life cycle network of these two fuels will be compared. The concept of recycling has been derived from ecological networks where materials are exchanged among different trophic levels that determine the stability and functioning of a particular ecosystem [2]. Life cycle networks also involve recycling of materials. From an environmental perspective recycling is good since the extraction of virgin materials is lower when recycling is done. Understanding the difference in structure of network for these two fuels and calculating recycling index and other network properties can reveal certain crucial features for assessing dynamic properties such as network resilience, which is an integral part of sustainability. Material cycling in industrial systems has been measured earlier [3] using different methods including the input-output physical flow analysis. Input-output metrics are more comprehensive since they can capture both the direct and indirect flows. In this work, the IO recycling metrics will be applied to gasoline and corn-ethanol for different important resources. The physical flow data for the networks will be taken from the Ecologically Based Life Cycle database [3, 4] which has been developed recently based on the Eco-LCA framework. [3] This life cycle inventory includes flow for different ecological resources for the US economy. Utilizing the IO recycling metrics for resources such as carbon, nitrogen and water flow will help determine the effect of using gasoline or corn ethanol on these resources. A high recycling index for water and nitrogen will be preferred from a sustainability perspective as it will lead to lower extraction of virgin materials and thereby reduce loss of these resources. Further, different sustainability measures can be explored by studying the recycling metrics for renewable and non-renewable resources. One of the key role of such network analysis will be to determine the processes which have lower recycling indices individually and therefore should be focused on to improve the sustainability of these fuel uses separately.

References

1.Hill et al., Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels. PNAS , volume 103, 30, 11206-11210, July 2006

2.Ulanowicz R.E., Quantitative methods for ecological network analysis. Computational Biology and Chemistry 28, 321-339, 2004

3.Bailey R., Bras B., Allen J.K., Measuring material cycling in industrial systems. Resources, Conservation and Recycling, Vol 52, 4, 643-652, 2008

4.Zhang Y., Baral A., Bakshi, B. R., Accounting for Ecosystem services in Life Cycle Assessment, Part II : Toward an Ecologically Based LCA, Environmental Science and Technology, 44, 7, 2624-2631, 2010.

5.The Eco-LCA tool : http://resilience.eng.ohio-state.edu/eco-lca/index.htm