Publications Published in Environ Sci Technol

1. Aerosol Transport in the California Central Valley Observed by Airborne Lidar. DeYoung, R. J.; Grant, W. B.; Severance, K..
   Environ Sci Technol: 2005
   Notes
   An aerosol lidar system was deployed on the NASA DC-8 and used to measure aerosol vertical profiles in the California Central Valley. The nadir-pointing Nd:YAG lidar operated at 532 and 1064 nm at 20 Hz. The resulting aerosol profiles were plotted in a unique three-dimensional format that allowed the visual observation of the aerosol scattering ratio profiles, the valley topography, and corresponding backward trajectory air masses. The accumulation of aerosols from the Bakersfield area can be seen in the southern end of the valley due to topography and prevailing winds.
   
   
   
2. Attenuation of Fluorocarbons Released from Foam Insulation in Landfills. Scheutz, C.; Dote, Y.; Fredenslund, A. M.; Mosbak, H.; Kjeldsen, P..
   Environ Sci Technol: 2007
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   Abstract: Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs) have been used as blowing agents (BAs) for foam insulation in home appliances and building materials, which after the end of their useful life are disposed of in landfills. The objective of this project was to evaluate the potential for degradation of BAs in landfills, and to develop a landfill model, which could simulate the fate of BAs in landfills. The investigation was performed by use of anaerobic microcosm studies using different types of organic waste and anaerobic digested sludge as inoculum. The BAs studied were CFC-11, CFC-12, HCFC-141b, HFC-134a, and HFC-245fa. Experiments considering the fate of some of the expected degradations products of CFC-11 and CFC-12 were included like HCFC-21, HCFC-22, HCFC-31, HCFC-32, and HFC-41. Degradation of all studied CFCs and HCFCs was observed regardless the type of waste used. In general, the degradation followed first-order kinetics. CFC-11 was rapidly degraded from 590 g L-1 to less than 5 g L-1 within 15-20 days. The degradation pattern indicated a sequential production of HCFC-21, HCFC-31, and HFC-41. However, the production of degradation products did not correlate with a stoichiometric removal of CFC-11 indicating that other degradation products were produced. HCFC-21 and HCFC-31 were further degraded whereas no further degradation of HFC-41 was observed. The degradation rate coefficient was directly correlated with the number of chlorine atoms attached to the carbon. The highest degradation rate coefficient was obtained for CFC-11, whereas lower rates were seen for HCFC-21 and HCFC-31. Equivalent results were obtained for CFC-12. HCFC-141b was also degraded with rates comparable to HCFC-21 and CFC-12. Anaerobic degradation of the studied HFCs was not observed in any of the experiments within a run time of up to 200 days. The obtained degradation rate coefficients were used as input for an extended version of an existing landfill fate model incorporating a time dependent BA release from co-disposed foam insulation waste. Predictions with the model indicate that the emission of foam released BAs may be strongly attenuated by microbial degradation reactions. Sensitivity analysis suggests that there is a need for determination of degradation rates under more field realistic scenarios.
   
   
   
3. Can Reducing Black Carbon Emissions Counteract Global Warming?. Bond, T. C.; Sun, H..
   Environ Sci Technol: 2005
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   Abstract: Field measurements and model results have recently shown that aerosols may have important climatic impacts. One line of inquiry has investigated whether reducing climate-warming soot or black carbon aerosol emissions can form a viable component of mitigating global warming. We review and acknowledge scientific arguments against considering aerosols and greenhouse gases in a common framework, including the differences in the physical mechanisms of climate change and relevant time scales. We argue that such a joint consideration is consistent with the language of the United Nations Framework Convention on Climate Change. We synthesize results from published climate-modeling studies to obtain a global warming potential for black carbon relative to that of CO2 (680 on a 100 year basis). This calculation enables a discussion of cost-effectiveness for mitigating the largest sources of black carbon. We find that many emission reductions are either expensive or difficult to enact when compared with greenhouse gases, particularly in Annex I countries. Finally, we propose a role for black carbon in climate mitigation strategies that is consistent with the apparently conflicting arguments raised during our discussion. Addressing these emissions is a promising way to reduce climatic interference primarily for nations that have not yet agreed to address greenhouse gas emissions and provides the potential for a parallel climate agreement.
   
   
   
4. Changes in the Regional Emissions of Greenhouse Gases and Ozone-Depleting Compounds. Khalil, M. A. K.; Rasmussen, R. A..
   Environ Sci Technol: 2004
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   Abstract: In the wake of the Kyoto and Montreal Protocols, there is a need to verify whether policies to reduce emissions are working. We present data showing that emissions of ozone-depleting compounds, such as the chlorofluorocarbons and methyl chloroform, are decreasing from some regions of the United States but emissions of the greenhouse gases do not appear to be declining.
   
   
   
5. CO2 Embodied in International Trade with Implications for Global Climate Policy. Peters, Glen P.; Hertwich, Edgar G..
   Environ Sci Technol: 2008
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   The flow of pollution through international trade flows has the ability to undermine environmental policies, particularly for global pollutants. In this article we determine the CO2 emissions embodied in international trade among 87 countries for the year 2001. We find that globally there are over 5.3 Gt of CO2 embodied in trade and that Annex B countries are net importers of CO2 emissions. Depending on country characteristics such as size variables and geographic location there are considerable variations in the embodied emissions. We argue that emissions embodied in trade may have a significant impact on participation in and effectiveness of global climate policies such as the Kyoto Protocol. We discuss several policy options to reduce the impact of trade in global climate policy. If countries take binding commitments as a part of a coalition, instead of as individual countries, then the impacts of trade can be substantially reduced. Adjusting emission inventories for trade gives a more consistent description of a country s environmental pressures and circumvents many trade related issues. It also gives opportunities to exploit trade as a means of mitigating emissions. Not least, a better understanding of the role that trade plays in a country s economic and environmental development will help design more effective and participatory climate policy post-Kyoto.
   
   
   
6. Comparative Life Cycle Assessment of Standard and Green Roofs. Saiz, S.; Kennedy, C.; Bass, B.; Pressnail, K..
   Environ Sci Technol: 2006
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   Abstract: Life cycle assessment (LCA) is used to evaluate the benefits, primarily from reduced energy consumption, resulting from the addition of a green roof to an eight story residential building in Madrid. Building energy use is simulated and a bottom-up LCA is conducted assuming a 50 year building life. The key property of a green roof is its low solar absorptance, which causes lower surface temperature, thereby reducing the heat flux through the roof. Savings in annual energy use are just over 1%, but summer cooling load is reduced by over 6% and reductions in peak hour cooling load in the upper floors reach 25%. By replacing the common flat roof with a green roof, environmental impacts are reduced by between 1.0 and 5.3%. Similar reductions might be achieved by using a white roof with additional insulation for winter, but more substantial reductions are achieved if common use of green roofs leads to reductions in the urban heat island.
   
   
   
7. Effect of Government Actions on Technological Innovation for SO2 Control. Taylor, M. R.; Rubin, E. S.; Hounshell, D. A..
   Environ Sci Technol: 2003
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   Abstract: The relationship between government actions and innovation in environmental control technology is important for the design of cost-effective policies to achieve environmental goals. This paper examines such relationships for the case of sulfur dioxide control technology for U.S. coal-fired power plants. The study employs several complementary research methods, including analyses of key government actions, technology patenting activity, technology performance and cost trends, knowledge transfer activities, and expert elicitations. Our results indicate that government regulation appears to be a greater stimulus to inventive activity than government-sponsored research support alone, and that the anticipation of regulation also spurs inventive activity. Regulatory stringency focuses this activity along particular technical pathways and is a key factor in creating markets for environmental technologies. We also find that with greater technology adoption, both new and existing systems experience notable efficiency improvements and capital cost reductions. The important role of government in fostering knowledge transfer via technical conferences and other measures is also seen as an important factor in promoting environmental technology innovation.
   
   
   
8. Energy and Material Balance of CO2 Capture from Ambient Air. Zeman, F..
   Environ Sci Technol: 2007
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   Abstract: Current Carbon Capture and Storage (CCS) technologies focus on large, stationary sources that produce approximately 50% of global CO2 emissions. We propose an industrial technology that captures CO2 directly from ambient air to target the remaining emissions. First, a wet scrubbing technique absorbs CO2 into a sodium hydroxide solution. The resultant carbonate is transferred from sodium ions to calcium ions via causticization. The captured CO2 is released from the calcium carbonate through thermal calcination in a modified kiln. The energy consumption is calculated as 350 kJ/mol of CO2 captured. It is dominated by the thermal energy demand of the kiln and the mechanical power required for air movement. The low concentration of CO2 in air requires a throughput of 3 million cubic meters of air per ton of CO2 removed, which could result in significant water losses. Electricity consumption in the process results in CO2 emissions and the use of coal power would significantly reduce to net amount captured. The thermodynamic efficiency of this process is low but comparable to other "end of pipe" capture technologies. As another carbon mitigation technology, air capture could allow for the continued use of liquid hydrocarbon fuels in the transportation sector.
   
   
   
9. Environmental and Energy Implications of Plug-In Hybrid-Electric Vehicles. Stephan, Craig H.; Sullivan, John.
   Environ Sci Technol: 2008
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   We analyze the effect of charging a significant number of plug-in hybrid vehicles (PHEVs) in the United States using presently available night-time spare electric capacity in the short term and new base-load capacity in the long term. Nationwide, there is currently ample spare night-time utility capacity to charge even a large fleet of PHEVs. Using the mix of generating plants expected to be used for PHEV charging, we find that, while driving on battery power, PHEVs compared to their conventional hybrid counterparts reduce CO2 emissions by 25% in the short term and as much as 50% in the long term. The short-term fractional increase in demand for margin fuels such as natural gas is found to be roughly twice the fractional penetration of PHEVs into the nationwide light-duty vehicle fleet. We also compare, on an energy basis, the CO2 savings of replacing coal plants versus replacing conventional vehicles with PHEVs. The result is found to depend critically on the fuel economy of the vehicles displaced by the PHEVs.
   
   
   
10. Ethanol's Energy Return on Investment: A Survey of the Literature 1990-Present. Hammerschlag, R..
    Environ Sci Technol: 2006
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    Abstract: Various authors have reported conflicting values for the energy return on investment (rE) of ethanol manufacture. Energy policy analysts predisposed to or against ethanol frequently cite selections from these studies to support their positions. This literature review takes an objective look at the disagreement by normalizing and comparing the data sets from ten such studies. Six of the reviewed studies treat starch ethanol from corn, and four treat cellulosic ethanol. Each normalized data set is also submitted to a uniform calculation of rE defined as the total product energy divided by nonrenewable energy input to its manufacture. Defined this way rE > 1 indicates that the ethanol product has nominally captured at least some renewable energy, and rE > 0.76 indicates that it consumes less nonrenewable energy in its manufacture than gasoline. The reviewed corn ethanol studies imply 0.84 rE 1.65; three of the cellulosic ethanol studies imply 4.40 rE 6.61. The fourth cellulosic ethanol study reports rE = 0.69 and may reasonably be considered an outlier.