(364a) Understanding the Carbon-Nitrogen-Water-Energy Nexus in the US Economy Via Eco-LCA

Complex interactions between multiple variables due to the environmental impacts of human activities motivate their joint analysis. This presentation will shed light on the nexus between carbon flows, reactive nitrogen flows, water use, and energy use in the United States economy. The interaction between global climate change, use of fossil fuels as energy resources, and emissions of carbon dioxide and other greenhouse gases is well known [1]. In addition, the use of energy resources, particularly for thermo-electric power generation also relies heavily on the use of water. Encouraging the use of biomass is commonly thought to reduce carbon intensity, but growing biomass often requires large quantities of water for irrigation and mobilizes more reactive nitrogen than can be handled by the ecosystem's carrying capacity. Aquatic runoff of excess fertilizers is known to cause eutrohpication, and emissions of nitrous oxide due to ammonium fertilizer use contribute to climate change [3]. Thus, products that may have smaller footprints of carbon and fossil energy, may have larger footprints of water [4] and nitrogen. Data about these and many other resource flows have been included in the recently developed framework for ecologically-based life cycle assessment (Eco-LCA) [2]. A model of the U.S. economy has been developed based on this framework and is available on-line. In this presentation, this model will be used to understand the carbon-nitrogen-water-energy nexus for nearly 500 sectors of the U.S. economy. Multivariate statistical methods such as principal component analysis will be used to understand the relationship between the selected four footprints. This approach will be applied to the entire economy and also to categories such as agriculture, manufacturing and service industries. Such analysis will be useful for understanding redundant and essential resources, and provide statistically meaningful univariate metrics. Additional metrics such as the ratio of various footprints will also be defined and evaluated for their ability to provide useful insight. Since the Eco-LCA model used in this work incorporates an economic input-output model, it can also provide insight into the short term effect of consumer activities, government taxes and other economic activities. This will be illustrated in this work by simulating the effect of carbon taxes.

References

1. Environmental Protection Agency : http://www.epa.gov/climatechange/

2. The Ecologically Based Life Cycle Analysis : http://resilience.eng.ohio-state.edu/eco-lca/

3. Vitousek et al. ?Human Alteration of the global nitrogen cycle : sources and consequences?. Ecological Applications, Volume 7, Issue 3 (August 1997)

4. Hoekstra A.Y. and Chapagain A.K. ?Water footprints of nations: Water use by people as a function of their consumption pattern?. Integrated Assessment of Water Resources and Global Change. Springer Netherlands.