This session has a very loose underlying theme of waste resource management. Waste management is an issue that is central to modern society. Growing populations and increasing standards of living give rise to increase resource use and waste production. Society has had to learn how to management this waste in an effective manner. The trends in carbon management and resource management have brought attention to this area as an avenue to reduce carbon impacts and to more efficiently utilize the resources available.
Lessons Learned From the Carbon Footprint of a City
ABSTRACT. The City of Beaumont, Texas carbon footprint described by this paper will be used by city government officials as part of an effort to reduce operating costs consistent with lower operating budget needs. This is a screening footprint that will attempt to capture major contributors based on results of other city footprints and established protocols.
System boundaries for city footprints can be defined with the city government’s infrastructure as the focus, or more holistically to gain an understanding of the population and what impacts are important to the public. While the larger focus is more broadly appealing, the narrower focus (e.g., that specified by C40 for Carbon Disclosure Project reporting) is more in keeping with the business needs of a city and was the approach selected for this study.
The city has eliminated curb-side recycling as a cost reduction, while larger cities have been adding this. Results show how current impacts related to waste management would compare to those for recycling. The city operates a propane-fueled bus system but ridership is very low. Results show impacts from transportation and user ridership data to compare to conventional programs elsewhere. Building operation data (e.g., utility use) is compared to other cities to show whether other cities that have invested in improvements are getting those benefits.
One unique issue that has been investigated makes the presentation of these results especially interesting. Most carbon footprints do not consider the impacts of traffic idle time. This study includes data on traffic idling where a major road repair at a river bridge impacts traffic on a heavily congested east-west interstate highway that runs right past its downtown area. Traffic back-ups occur each afternoon for east-bound travelers and they last for many hours, bringing thousands of cars and cargo trucks to a stop or crawl. Impacts from traffic idling and low speed travel are compared to other aspects of city operations to gain better perspective on this anomaly. A portion of city workers use this bridge as part of their daily commute home from work. Possible mitigating actions are recommended. Idling impacts have not been shared elsewhere.
|16:15||Bobby Renz, Christopher Evans, Morton Barlaz, Jim Levis, Tiffany Kollar and Claire Boland
Developing Energy and Greenhouse Gas Emission Factors for Anaerobic Digestion in U.S. EPA’s Waste Reduction Model
ABSTRACT. Food waste and yard trimmings accounted for 29.8% of municipal solids waste (MSW) discards in the United States in 2012, with just 4.8% of food waste recovered from disposal. While source reduction and food donation are the preferred food waste management options, anaerobic digestion is an emerging management strategy that cities will likely employ as they pursue organics landfill diversion targets and requirements, such as Massachusetts’ recent commercial food waste disposal ban. The authors are working with the U.S. EPA to develop life-cycle energy and greenhouse gas (GHG) emission factors for anaerobic digestion of organics in EPA’s Waste Reduction Model (WARM).
WARM was developed to help solid waste planners and organizations track and voluntarily report GHG emissions reductions from several different waste management practices. The authors are developing an approach for modeling anaerobic digestion in WARM based on a literature review, stakeholder interviews, and adaptation of an existing model developed at North Carolina State University. Anaerobic digestion produces two potentially valuable coproducts: biogas and digested liquids and solids (digestate). The boundaries of the anaerobic digestion energy and GHG emission factors in WARM will include all gate-to-gate processes at the digester and cradle-to-grave impacts from beneficial use and disposal of coproducts. The modeling approach addresses the effect of technology type and feedstock composition on coproducts yield, impacts from co-digestion at wastewater treatment plants, and impacts from different options for utilizing generated biogas and digestate.
Preliminary estimates indicate that the digester technology modeled is likely to have a minor impact on life-cycle emissions, while beneficial use and management of biogas and digestate is expected to have a larger impact on life-cycle energy and emissions. The authors are currently evaluating impacts from synthetic fertilizer use avoided by land application of digestate and electricity and heat generation from biogas. Previous studies have found that total GHG emissions from anaerobic digestion ranging from -47 to 29 kg CO2e/ww Mg of household organic waste. The large values and ranges for these values indicate that further research is needed to identify potential life-cycle emissions from U.S. anaerobic digestion facilities.
The development of national average factors for anaerobic digestion in WARM will provide insight into the environmental impacts of organics diversion and beneficial use of coproducts. These emission factors will provide waste managers and policy-makers with a more complete perspective on the life-cycle impacts from different material management options.
 U.S. EPA. 2014. “Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2012.” United States Environmental Protection Agency. EPA-530-F-14-001. Retrieved from: http://www.epa.gov/solidwaste/nonhaz/municipal/pubs/2012_msw_fs.pdf.  Levis, J.W. & M.A. Barlaz. 2013. Anaerobic Digestion Process Model Documentation. Retrieved from: http://www4.ncsu.edu/~jwlevis/AD.pdf. Accessed: April 30, 2015.  Møller, J., A. Boldrin, and T.H. Christensen. 2009. Anaerobic digestion and digestate use: accounting of greenhouse gases and global warming contribution. Waste Management & Research: The Journal of the International Solid Wastes and Public Cleansing Association, ISWA, 27(8), 813–24. doi:10.1177/0734242X09344876
|16:30||Florian Gehring, Roberta Graf, Severin Seifert and Jan Paul Lindner
Recycling – Is there an ecological benefit of secondary commodity sources? A methodic approach
ABSTRACT. The recycling of materials is one essential part of today’s strategies to cover future commodity needs. For this resource-conserving approach new recycling treatments are developed constantly. New recycling ways need to be evaluated, to verify their economic and environmental benefit in comparison to the primary production. Due to the laboratory scale and the linked uncertainties, methods are crucial which enable a sound comparison of diverse material provision options.
Within the presented project, which was funded by the Gips-Schüle foundation, the recycling of electronic scrap was tested. An innovative approach named electrodynamic fragmentation was enhanced by Fraunhofer Institute for Building Physics (IBP) to that effect. Besides the process adaption, a further emphasize of the study was the identification of target materials in electronic scrap and the evaluation of their recovery potential from an environmental perspective. The ecological benefit was quantified by life cycle assessment (lca). Thereby one main methodical challenge consisted of the creation of comparability of diverse commodity sources. A generalization of the value chain of recycling was necessary as well as a survey of the requirements the secondary material has to meet to be comparable.
The presentation focuses on the methodical approaches to achieve comparability for commodity sources. The identified value chain of recycling and the linked quality gates are illustrated as well as exemplary environmental potentials of the recovery of target materials.
For the future provision of industry and society with crucial materials, recycling seems to be the logical consequence. In order to choose recycling procedures with the highest environmental benefit, a broad basis of information is needed and realistic comparability of data is vital. The presented study provides the methodical approach to achieve comparability and delivers insights in the environmental recycling potential of some target commodities. The study enables decision makers in politics and industry to justify their recycling decisions.
|16:45||Roland Geyer, Brandon Kuczenski, Trevor Zink and Ashley Henderson
Four Common Misconceptions about Recycling
ABSTRACT. The recycling of material resources lies at the heart of the industrial ecology metaphor. The very notion of the industrial ecosystem is motivated by the idea that we should learn from natural ecosystems how to ‘close the loop’. Recycling is not just central to industrial ecology (IE), it is part of everyday life. Yet, while virtually no one questions the environmental rationale behind recycling, accurately quantifying its environmental benefits is not a trivial problem. Part of this issue are four common misconceptions about recycling that may lead to misguided actions and policies and could thus undermine recycling’s environmental potential. They are: 1) Recycling material multiple times is better than once, 2) Closed-loop recycling is better than open-loop recycling, 3) Given its inherent properties are unchanged, recycled material displaces primary material one to one, and 4) The distinction between closed and open loops is useful. This talk will explain why those four assertions are flawed, discuss the implications, and present an alternative set of principles to better harness the potential environmental benefits of closing material loops.