@article{sardarmehni_anchieta_levis_2022, title={Solid waste optimization life-cycle framework in Python (SwolfPy)}, volume={1}, ISSN={["1530-9290"]}, url={https://doi.org/10.1111/jiec.13236}, DOI={10.1111/jiec.13236}, abstractNote={This paper describes a novel open‐source life‐cycle optimization framework for solid waste and sustainable materials management applications named solid waste optimization life‐cycle framework in Python (SwolfPy). The current version includes life‐cycle models for landfills, mass burn waste‐to‐energy, gasification, centralized composting, home composting, anaerobic digestion, material recovery facilities, refuse‐derived fuel facilities, material recycling, transfer stations, and single‐family collection. Compared to existing frameworks, SwolfPy streamlines data input/output processes, improves model integration and modularity, provides a wide variety of data visualization and customization, speeds up uncertainty analysis and optimization, and has a user‐friendly graphical user interface (GUI). SwolfPy's GUI allows users to define solid waste management networks and scenarios as well as perform comparative life cycle assessments (LCAs), contribution analyses, uncertainty analyses, and optimization. SwolfPy is implemented in Python using Pandas, NumPy, and SciPy for computational tasks, PySide2 for creating the GUI, and Brightway2 for storing life‐cycle inventory data and performing the LCA calculations. SwolfPy is modular and flexible, which enables it to be easily coupled with other packages and to facilitate the addition of new processes, materials, environmental flows and impacts, and methodologies. SwolfPy uses sequential least‐squares programming for constrained nonlinear optimization to find systems and strategies that minimize cost or environmental emissions and impacts while meeting user‐defined constraints. An illustrative case study with 44 materials, 4 collection processes, and 6 treatment processes is presented, and SwolfPy performs 10,000 Monte Carlo iterations in 16 min and finds optimal solutions in 10–25 min on a Windows 10 machine with a CPU speed of 3.60 GHz and 8 logical processors. This article met the requirements for a Gold‐Gold Badge. JIE data openness badge described at http://jie.click/badges.}, journal={JOURNAL OF INDUSTRIAL ECOLOGY}, publisher={Wiley}, author={Sardarmehni, Mojtaba and Anchieta, Pedro H. Chagas and Levis, James W.}, year={2022}, month={Jan} }
 @article{wang_levis_barlaz_2021, title={Development of Streamlined Life-Cycle Assessment for the Solid Waste Management System}, volume={55}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.0c07461}, DOI={10.1021/acs.est.0c07461}, abstractNote={Life-cycle assessments (LCAs) of municipal solid waste management (MSWM) systems are time- and data-intensive. Reducing the data requirements for inventory and impact assessments will facilitate the wider use of LCAs during early system planning and design. Therefore, the objective of this study is to develop a systematic framework for streamlining LCAs by identifying the most critical impacts, life-cycle inventory emissions, and inputs based on their contributions to the total impacts and their effect on the rankings of 18 alternative MSWM scenarios. The scenarios are composed of six treatment processes: landfills, waste-to-energy combustion, single-stream recycling, mixed waste recycling, anaerobic digestion, and composting. The full LCA uses 1752 flows of resources and emissions, 10 impact categories, 3 normalization references, and 7 weighting schemes, and these were reduced using the streamlined LCA approach proposed in this study. Human health cancer, ecotoxicity, eutrophication, and fossil fuel depletion contribute 75-83% to the total impacts across all scenarios. It was found that 3.3% of the inventory flows contribute ≥95% of the overall environmental impact. The highest-ranked strategies are consistent between the streamlined and full LCAs. The results provide guidance on which impacts, flows, and inputs to prioritize during early strategy design.}, number={8}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Wang, Yixuan and Levis, James W. and Barlaz, Morton A.}, year={2021}, month={Mar}, pages={5475–5484} }
 @article{wang_levis_barlaz_2021, title={Life-Cycle Assessment of a Regulatory Compliant US Municipal Solid Waste Landfill}, volume={55}, ISSN={["1520-5851"]}, url={https://doi.org/10.1021/acs.est.1c02526}, DOI={10.1021/acs.est.1c02526}, abstractNote={Landfills receive over half of all U.S. municipal solid waste (MSW) and are the third largest source of anthropogenic methane emissions. Life-cycle assessment (LCA) of landfills is complicated by the long duration of waste disposal, gas generation and control, and the time over which the engineered infrastructure must perform. The objective of this study is to develop an LCA model for a representative U.S. MSW landfill that is responsive to landfill size, regulatory thresholds for landfill gas (LFG) collection and control, practices for LFG management (i.e., passive venting, flare, combustion for energy recovery), and four alternative schedules for LFG collection well installation. Material production required for construction and operation contributes 68-75% to toxicity impacts, while LFG emissions contribute 50-99% to global warming, ozone depletion, and smog impacts. The current non-methane organic compound regulatory threshold (34 Mg yr-1) reduces methane emissions by <7% relative to the former threshold (50 Mg yr-1). Requiring landfills to continue collecting LFG until the flow rate is <10 m3 min-1 reduces emissions by 20-52%, depending on the waste decay rate. In general, for landfills already required to collect gas, collecting gas longer is more important than collecting gas earlier to reduce methane emissions.}, number={20}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, publisher={American Chemical Society (ACS)}, author={Wang, Yixuan and Levis, James W. and Barlaz, Morton A.}, year={2021}, month={Oct}, pages={13583–13592} }
 @article{sardarmehni_levis_2021, title={Life-cycle modeling of nutrient and energy recovery through mixed waste processing systems}, volume={169}, ISSN={["1879-0658"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85102536147&partnerID=MN8TOARS}, DOI={10.1016/j.resconrec.2021.105503}, abstractNote={There is increasing interest in recovering nutrients and energy from the organic fraction of municipal solid waste (OFMSW). Given the costs associated with separate collection of OFMSW, and the potential difficulty in finding clean feedstocks, there are potential benefits in beneficial recovery of OFMSW as part of residual MSW. Therefore, this study compared the life-cycle impacts associated with management alternatives for recovering energy and/or nutrients from the OFMSW through mixed waste processing systems. The considered treatment alternatives include landfilling, mass burn waste-to-energy, gasification and syngas combustion (GC) for electricity production, gasification Fischer–Tropsch (GFT) for transportation fuel production, aerobic composting (AC), and anaerobic digestion (AD). Seven environmental impacts include global warming potential (GWP), cumulative energy demand, acidification, eutrophication, photochemical oxidation, ecotoxicity, and human toxicity were assessed for five sets of state and one U.S. national waste compositions. The mass burn waste-to-energy and GC scenarios generally have the lowest environmental impacts, while landfilling and GFT have the greatest impacts. Separating out organics for AC increased environmental impacts compared to sending them to GC, while sending them to AD decreased GWP and increased the other impacts. Sensitivity analyses suggest that these conclusions are generally robust to uncertainty in input values.}, journal={RESOURCES CONSERVATION AND RECYCLING}, author={Sardarmehni, Mojtaba and Levis, James W.}, year={2021}, month={Jun} }
 @article{puhl_fritch_lane_tse_yount_sacramento_fintelman-rodrigues_tavella_costa_weston_et al._2021, title={Repurposing the Ebola and Marburg Virus Inhibitors Tilorone, Quinacrine, and Pyronaridine: In Vitro Activity against SARS-CoV-2 and Potential Mechanisms}, volume={6}, ISSN={["2470-1343"]}, DOI={10.1021/acsomega.0c05996}, abstractNote={Severe acute respiratory coronavirus 2 (SARS-CoV-2) is a newly identified virus that has resulted in over 2.5 million deaths globally and over 116 million cases globally in March, 2021. Small-molecule inhibitors that reverse disease severity have proven difficult to discover. One of the key approaches that has been widely applied in an effort to speed up the translation of drugs is drug repurposing. A few drugs have shown in vitro activity against Ebola viruses and demonstrated activity against SARS-CoV-2 in vivo. Most notably, the RNA polymerase targeting remdesivir demonstrated activity in vitro and efficacy in the early stage of the disease in humans. Testing other small-molecule drugs that are active against Ebola viruses (EBOVs) would appear a reasonable strategy to evaluate their potential for SARS-CoV-2. We have previously repurposed pyronaridine, tilorone, and quinacrine (from malaria, influenza, and antiprotozoal uses, respectively) as inhibitors of Ebola and Marburg viruses in vitro in HeLa cells and mouse-adapted EBOV in mice in vivo. We have now tested these three drugs in various cell lines (VeroE6, Vero76, Caco-2, Calu-3, A549-ACE2, HUH-7, and monocytes) infected with SARS-CoV-2 as well as other viruses (including MHV and HCoV 229E). The compilation of these results indicated considerable variability in antiviral activity observed across cell lines. We found that tilorone and pyronaridine inhibited the virus replication in A549-ACE2 cells with IC50 values of 180 nM and IC50 198 nM, respectively. We used microscale thermophoresis to test the binding of these molecules to the spike protein, and tilorone and pyronaridine bind to the spike receptor binding domain protein with Kd values of 339 and 647 nM, respectively. Human Cmax for pyronaridine and quinacrine is greater than the IC50 observed in A549-ACE2 cells. We also provide novel insights into the mechanism of these compounds which is likely lysosomotropic.}, number={11}, journal={ACS OMEGA}, author={Puhl, Ana C. and Fritch, Ethan J. and Lane, Thomas R. and Tse, Longping V and Yount, Boyd L. and Sacramento, Carolina Q. and Fintelman-Rodrigues, Natalia and Tavella, Tatyana Almeida and Costa, Fabio Trindade Maranhao and Weston, Stuart and et al.}, year={2021}, month={Mar}, pages={7454–7468} }
 @article{sardarmehni_levis_barlaz_2021, title={What Is the Best End Use for Compost Derived from the Organic Fraction of Municipal Solid Waste?}, volume={55}, ISBN={1520-5851}, url={https://doi.org/10.1021/acs.est.0c04997}, DOI={10.1021/acs.est.0c04997}, abstractNote={There is increasing interest in diverting the organic fraction of municipal solid waste from landfills to biological treatment processes that result in compost. Due to variations in compost quality and available markets, it is not always possible for compost to be beneficially used on soil. In such cases, compost may be used as alternative daily cover (ADC) in landfills. The objective of this study is to compare the environmental impacts of using compost as a soil amendment, accounting for its beneficial substitutions for fertilizer and peat, to its use as ADC. Monte Carlo simulation and parametric sensitivity analyses were performed to evaluate the effects of uncertainty in input values on the environmental performance. The ADC scenario outperforms the soil amendment scenario in terms of global warming potential, acidification, and eutrophication in ∼63, ∼77, and ∼100% of simulations, respectively, while the soil amendment scenario is better in terms of cumulative energy demand and abiotic resource depletion potential ∼94 and ∼96% of the time, respectively. Therefore, we recommend that using compost as ADC be considered, especially when site-specific factors such as feedstock contamination or a lack of markets make it difficult to find appropriate applications for compost as a soil amendment.}, number={1}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, publisher={American Chemical Society (ACS)}, author={Sardarmehni, Mojtaba and Levis, James W. and Barlaz, Morton A.}, year={2021}, pages={73–81} }
 @article{wang_levis_barlaz_2020, title={An Assessment of the Dynamic Global Warming Impact Associated with Long-Term Emissions from Landfills}, volume={54}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.9b04066}, abstractNote={Landfills are a major contributor of anthropogenic CH4 emissions. Since the greenhouse gas (GHG) emissions associated with landfilling waste can occur over decades to centuries, the standard static approach to estimating global warming impacts may not accurately represent the global warming impacts of landfills. The objective of this study is to assess the implications of using 100-yr and 20-yr static and dynamic global warming potential (GWP) approaches to estimate the global warming impacts from municipal solid waste landfills. A life-cycle model was developed to estimate GHG emissions for three gas treatment cases (passive venting, flare, CH4 conversion to electricity) and four decay rates. For the 100-yr GWP, other model uncertainties (e.g., static GWP values, decay rate, moisture content, or gas collection efficiency) generally had a larger effect on the estimated global warming impact than the choice of static versus dynamic GWP methods. This shows that when comparing single-point GWP values, the choice of static versus dynamic is relatively unimportant for most landfills. While dynamic GWPs consider temporal variance and provide useful estimates for the warming over a set time horizon, for most comparative analyses, static values provide reasonable bounds for the actual 100-yr warming impact.}, number={3}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Wang, Yixuan and Levis, James W. and Barlaz, Morton A.}, year={2020}, month={Feb}, pages={1304–1313} }
 @article{christensen_damgaard_levis_zhao_bjorklund_arena_barlaz_starostina_boldrin_astrup_et al._2020, title={Application of LCA modelling in integrated waste management}, volume={118}, ISSN={["1879-2456"]}, DOI={10.1016/j.wasman.2020.08.034}, abstractNote={Life cycle assessment (LCA) has been used in waste management for the last two decades and hundreds of journal papers have been published. The use of LCA in waste management has provided a much-improved holistic view of waste management including waste flows and potential environmental impacts. Although much knowledge has been obtained from LCA studies, there is still a need to use LCA models in integrated waste management. This paper describes six areas where LCA is expected to play a role in waste management in the future: 1) understanding an existing waste management system; 2) improving existing waste management systems; 3) comparing alternative technologies/ technology performance; 4) technology development/prospective technologies; 5) policy development/strategic development; and 6) reporting. Illustrative examples are provided for each application area.}, journal={WASTE MANAGEMENT}, author={Christensen, T. H. and Damgaard, A. and Levis, J. and Zhao, Y. and Bjorklund, A. and Arena, U. and Barlaz, M. A. and Starostina, V and Boldrin, A. and Astrup, T. F. and et al.}, year={2020}, month={Dec}, pages={313–322} }
 @article{jaunich_levis_decarolis_barlaz_ranjithan_2020, title={Exploring alternative solid waste management strategies for achieving policy goals}, volume={53}, ISSN={0305-215X 1029-0273}, url={http://dx.doi.org/10.1080/0305215X.2020.1759578}, DOI={10.1080/0305215X.2020.1759578}, abstractNote={The authors previously analysed a real-world solid waste management (SWM) system using the solid waste optimization life-cycle framework (SWOLF) to identify optimal SWM strategies that meet modelled objectives (e.g. cost, environmental impacts, landfill diversion). While mathematically optimal strategies can support SWM decision making, they may not be readily implementable because of unmodelled objectives (e.g. practical limitations, social preferences, political and management considerations). A mathematical programming technique extending SWOLF is used to systematically identify, for several scenarios, different ‘optimal’ SWM strategies that are maximally different from each other in terms of waste flows, while meeting modelled objectives and constraints. The performance with respect to unmodelled issues was analysed to demonstrate the flexibility in potential strategies. Practitioner feedback highlighted implementation challenges due to existing practices; however, insights gained from this exercise led to more plausible and acceptable strategies by incrementally modifying the initial SWM alternatives generated.}, number={5}, journal={Engineering Optimization}, publisher={Informa UK Limited}, author={Jaunich, Megan K. and Levis, James W. and DeCarolis, Joseph F. and Barlaz, Morton A. and Ranjithan, S. Ranji}, year={2020}, month={Jun}, pages={1–14} }
 @article{henriksen_levis_barlaz_damgaard_2019, title={Approaches to fill data gaps and evaluate process completeness in LCA—perspectives from solid waste management systems}, volume={24}, ISSN={0948-3349 1614-7502}, url={http://dx.doi.org/10.1007/s11367-019-01592-z}, DOI={10.1007/s11367-019-01592-z}, abstractNote={Large data amounts are required in an LCA, but often, site-specific data are missing and less representative surrogate data must be used to fill data gaps. No standardized rules exist on how to address data gaps and process completeness. We suggest a systematic evaluation of process completeness, identification of data gaps, and application of surrogate values to fill the gaps. The study focus on foreground process data. A solid waste management (SWM) scenario was used to illustrate the suggested method. The expected input and output flows in a waste incineration model were identified based on legislation and expert judgment, after which process completeness scores were calculated and missing flows identified. To illustrate the use of different types of surrogate data to fill data gaps, data gaps were selected for 16 different parameters in five SWM processes. We compared the global warming potential (GWP) from using surrogate data, and from leaving the gap, to identify the data gaps where representative surrogate data should be used. The completeness score for the material inputs to waste incineration was 78%, and the missing flows were auxiliary fuels and precipitation chemicals. The completeness score for air emissions were between 38 and 50% with and without expert judgment. If only greenhouse gases were considered (CO2, CH4, and N2O), the completeness score would be 67%. Applying weighting factors according to the greenhouse gas contribution in the USA gave a completeness score of 94%. The system-wide data gaps, where representative surrogate data should be applied, were the CH4 release from composting; electricity generation efficiency of incineration; recovery efficiencies at a material recovery facility; and composition of the plastic, metal, and paper fractions in the household waste; in these cases, leaving the gap changed the GWP results by > 5%. Completeness evaluation should take into account the relevance and importance of flows; relevance depends on the considered life cycle impact methods and importance depends on the weighting of the different flows. The set of expected flows and evaluation of relevance and importance must be documented in a transparent manner. The choice of surrogate values to fill data gaps depends on the availability of secondary data and on whether the data gap matters, i.e., significantly affects the LCA results. The suggested method can be used to properly document the identification of missing flows and to select and apply surrogate values to fill the data gaps.}, number={9}, journal={The International Journal of Life Cycle Assessment}, publisher={Springer Science and Business Media LLC}, author={Henriksen, Trine and Levis, James W. and Barlaz, Morton A. and Damgaard, Anders}, year={2019}, month={Feb}, pages={1587–1601} }
 @article{cobo_levis_dominguez-ramos_irabien_2019, title={Economics of Enhancing Nutrient Circularity in an Organic Waste Valorization System}, volume={53}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.8b06035}, DOI={10.1021/acs.est.8b06035}, abstractNote={Waste managers struggle to comply with the European legislation that regulates the handling of organic waste. A waste management system that aims at recovering nutrients from the municipal organic waste generated in the Spanish region of Cantabria was modeled by combining material flow analysis, life cycle assessment, and life cycle costing. The model was optimized to find system configurations that minimize the total annual cost (TAC) and the global warming impacts (GW) and maximize the circularity indicators of nitrogen and phosphorus (CIN and CIP). The developed superstructure is composed of waste management unit processes and unit processes related to the land application of the recovered products (compost, digestate, (NH4)2SO4, and NH4MgPO4·6H2O) and industrial fertilizers to grow corn. The results of the optimization indicate that increasing CIN and minimizing GW raises the TAC, because of the investment in new technologies, although high CIP values can be achieved at low TACs. The economic margin that enables the organic fertilizers to compete in the market with industrial fertilizers was estimated. Cooperation between waste managers, the farmers that purchase the recovered products, and the policy-makers that set the waste management taxes can minimize the costs that hinder the transition toward a circular economy.}, number={11}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Cobo, Selene and Levis, James W. and Dominguez-Ramos, Antonio and Irabien, Angel}, year={2019}, month={May}, pages={6123–6132} }
 @article{jaunich_levis_decarolis_barlaz_ranjithan_2019, title={Solid Waste Management Policy Implications on Waste Process Choices and Systemwide Cost and Greenhouse Gas Performance}, volume={53}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.8b04589}, DOI={10.1021/acs.est.8b04589}, abstractNote={Solid waste management (SWM) is a key function of local government and is critical to protecting human health and the environment. Development of effective SWM strategies should consider comprehensive SWM process choices and policy implications on system-level cost and environmental performance. This analysis evaluated cost and select environmental implications of SWM policies for Wake County, North Carolina using a life-cycle approach. A county-specific data set and scenarios were developed to evaluate alternatives for residential municipal SWM, which included combinations of a mixed waste material recovery facility (MRF), anaerobic digestion, and waste-to-energy combustion in addition to existing SWM infrastructure (composting, landfilling, single stream recycling). Multiple landfill diversion and budget levels were considered for each scenario. At maximum diversion, the greenhouse gas (GHG) mitigation costs ranged from 30 to 900 $/MTCO2e; the lower values were when a mixed waste MRF was used, and the higher values when anaerobic digestion was used. Utilization of the mixed waste MRF was sensitive to the efficiency of material separation and operating cost. Maintaining the current separate collection scheme limited the potential for cost and GHG reductions. Municipalities seeking to cost-effectively increase landfill diversion while reducing GHGs should consider waste-to-energy, mixed waste separation, and changes to collection.}, number={4}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Jaunich, Megan K. and Levis, James W. and DeCarolis, Joseph F. and Barlaz, Morton A. and Ranjithan, S. Ranji}, year={2019}, month={Jan}, pages={1766–1775} }
 @article{grieger_bossa_levis_von borries_strader_cuchiara_hendren_hansen_jones_2018, title={Application and testing of risk screening tools for nanomaterial risk analysis}, volume={5}, ISSN={2051-8153 2051-8161}, url={http://dx.doi.org/10.1039/C8EN00518D}, DOI={10.1039/C8EN00518D}, abstractNote={This study applies and tests new risk screening tools for engineered nanomaterials and highlights key findings.}, number={8}, journal={Environmental Science: Nano}, publisher={Royal Society of Chemistry (RSC)}, author={Grieger, Khara and Bossa, Nathan and Levis, James W. and von Borries, Kerstin Johanna Felicitas and Strader, Phillip and Cuchiara, Maude and Hendren, Christine Ogilvie and Hansen, Steffen Foss and Jones, Jacob L.}, year={2018}, pages={1844–1858} }
 @article{levis_weisbrod_van hoof_barlaz_2017, title={A review of the airborne and waterborne emissions from uncontrolled solid waste disposal sites}, volume={47}, ISSN={1064-3389 1547-6537}, url={http://dx.doi.org/10.1080/10643389.2017.1342513}, DOI={10.1080/10643389.2017.1342513}, abstractNote={ABSTRACT The objective of this review is to critically analyze literature, data, and models on the environmental releases from the uncontrolled disposal and burning of solid waste. Major concerns include releases of greenhouse gases, particulate matter, and leachate. Many factors influence these releases including waste composition, site depth, and climate. While the impact of these factors is understood qualitatively, there is little data and considerable uncertainty in model predictions. One limitation is that in general, predicted emissions are not responsive to changes in waste composition. Estimating impacts to human health and the environment from the predicted emissions results in additional uncertainty.}, number={12}, journal={Critical Reviews in Environmental Science and Technology}, publisher={Informa UK Limited}, author={Levis, James W. and Weisbrod, Annie and Van Hoof, Gert and Barlaz, Morton A.}, year={2017}, month={Jun}, pages={1003–1041} }
 @article{stanisavljevic_levis_barlaz_2017, title={Application of a Life Cycle Model for European Union Policy-Driven Waste Management Decision Making in Emerging Economies}, volume={22}, ISSN={1088-1980}, url={http://dx.doi.org/10.1111/jiec.12564}, DOI={10.1111/jiec.12564}, abstractNote={Summary}, number={2}, journal={Journal of Industrial Ecology}, publisher={Wiley}, author={Stanisavljevic, Nemanja and Levis, James W. and Barlaz, Morton A.}, year={2017}, month={Mar}, pages={341–355} }
 @article{karam_mcmillan_lai_de los reyes_sederoff_grunden_ranjithan_levis_ducoste_2017, title={Construction and Setup of a Bench-scale Algal Photosynthetic Bioreactor with Temperature, Light, and pH Monitoring for Kinetic Growth Tests}, volume={6}, ISSN={1940-087X}, url={http://dx.doi.org/10.3791/55545}, DOI={10.3791/55545}, abstractNote={The optimal design and operation of photosynthetic bioreactors (PBRs) for microalgal cultivation is essential for improving the environmental and economic performance of microalgae-based biofuel production. Models that estimate microalgal growth under different conditions can help to optimize PBR design and operation. To be effective, the growth parameters used in these models must be accurately determined. Algal growth experiments are often constrained by the dynamic nature of the culture environment, and control systems are needed to accurately determine the kinetic parameters. The first step in setting up a controlled batch experiment is live data acquisition and monitoring. This protocol outlines a process for the assembly and operation of a bench-scale photosynthetic bioreactor that can be used to conduct microalgal growth experiments. This protocol describes how to size and assemble a flat-plate, bench-scale PBR from acrylic. It also details how to configure a PBR with continuous pH, light, and temperature monitoring using a data acquisition and control unit, analog sensors, and open-source data acquisition software.}, number={124}, journal={Journal of Visualized Experiments}, publisher={MyJove Corporation}, author={Karam, Amanda L. and McMillan, Catherine C. and Lai, Yi-Chun and de los Reyes, Francis L., III and Sederoff, Heike W. and Grunden, Amy M. and Ranjithan, Ranji S. and Levis, James W. and Ducoste, Joel J.}, year={2017}, month={Jun} }
 @article{martinez-sanchez_levis_damgaard_decarolis_barlaz_astrup_2017, title={Evaluation of Externality Costs in Life-Cycle Optimization of Municipal Solid Waste Management Systems}, volume={51}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.6b06125}, DOI={10.1021/acs.est.6b06125}, abstractNote={The development of sustainable solid waste management (SWM) systems requires consideration of both economic and environmental impacts. Societal life-cycle costing (S-LCC) provides a quantitative framework to estimate both economic and environmental impacts, by including "budget costs" and "externality costs". Budget costs include market goods and services (economic impact), whereas externality costs include effects outside the economic system (e.g., environmental impact). This study demonstrates the applicability of S-LCC to SWM life-cycle optimization through a case study based on an average suburban U.S. county of 500 000 people generating 320 000 Mg of waste annually. Estimated externality costs are based on emissions of CO2, CH4, N2O, PM2.5, PM10, NOx, SO2, VOC, CO, NH3, Hg, Pb, Cd, Cr (VI), Ni, As, and dioxins. The results indicate that incorporating S-LCC into optimized SWM strategy development encourages the use of a mixed waste material recovery facility with residues going to incineration, and separated organics to anaerobic digestion. Results are sensitive to waste composition, energy mix and recycling rates. Most of the externality costs stem from SO2, NOx, PM2.5, CH4, fossil CO2, and NH3 emissions. S-LCC proved to be a valuable tool for policy analysis, but additional data on key externality costs such as organic compounds emissions to water would improve future analyses.}, number={6}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Martinez-Sanchez, Veronica and Levis, James W. and Damgaard, Anders and DeCarolis, Joseph F. and Barlaz, Morton A. and Astrup, Thomas F.}, year={2017}, month={Mar}, pages={3119–3127} }
 @inproceedings{levis_barlaz_2017, title={Life-cycle modeling of municipal solid waste landfills}, DOI={10.1061/9780784480434.038}, abstractNote={Landfills that receive municipal solid waste represent a critical component of solid waste infrastructure in the U.S. and are a leading source of greenhouse gas emissions. Thus, it is critical to understand the factors that control the environmental performance of landfills. Life-cycle modeling of landfills is complex, as landfills constantly change over time. The objective of this research was to develop a life-cycle model of an average ton of municipal solid waste disposed in a “national average” landfill. The framework considers critical factors relating to the temporal changes in landfill gas generation, collection, beneficial use, and oxidation. The model calculates temporally averaged landfill gas collection efficiencies for individual waste components in consideration of the aforementioned factors. The results indicate that for mixed waste, 12 to 41% of the generated methane becomes fugitive emissions. The results also show the significant potential benefits of earlier landfill gas collection.}, number={276}, booktitle={Geotechnical frontiers 2017: waste containment, barriers, remediation, and sustainable geoengineering}, author={Levis, J. W. and Barlaz, Morton}, year={2017}, pages={355–368} }
 @article{lang_allred_field_levis_barlaz_2017, title={National Estimate of Per- and Polyfluoroalkyl Substance (PFAS) Release to U.S. Municipal Landfill Leachate}, volume={51}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.6b05005}, DOI={10.1021/acs.est.6b05005}, abstractNote={Landfills are the final stage in the life cycle of many products containing per- and polyfluoroalkyl substances (PFASs) and their presence has been reported in landfill leachate. The concentrations of 70 PFASs in 95 samples of leachate were measured in a survey of U.S. landfills of varying climates and waste ages. National release of PFASs was estimated by coupling measured concentrations for the 19 PFASs where more than 50% of samples had quantifiable concentrations, with climate-specific estimates of annual leachate volumes. For 2013, the total volume of leachate generated in the U.S. was estimated to be 61.1 million m3, with 79% of this volume coming from landfills in wet climates (>75 cm/yr precipitation) that contain 47% of U.S. solid waste. The mass of measured PFASs from U.S. landfill leachate to wastewater treatment plants was estimated to be between 563 and 638 kg for 2013. In the majority of landfill leachate samples, 5:3 fluorotelomer carboxylic acid (FTCA) was dominant and variations in concentrations with waste age affected total estimated mass. There were six PFASs that demonstrated significantly higher concentrations in leachate from younger waste compared to older waste and six PFAS demonstrated significant variation with climate.}, number={4}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Lang, Johnsie R. and Allred, B. McKay and Field, Jennifer A. and Levis, James W. and Barlaz, Morton A.}, year={2017}, month={Feb}, pages={2197–2205} }
 @article{jaunich_levis_decarolis_gaston_barlaz_bartelt-hunt_jones_hauser_jaikumar_2016, title={Characterization of municipal solid waste collection operations}, volume={114}, ISSN={0921-3449}, url={http://dx.doi.org/10.1016/j.resconrec.2016.07.012}, DOI={10.1016/j.resconrec.2016.07.012}, abstractNote={Solid waste collection contributes to the cost, emissions, and fossil fuel required to manage municipal solid waste. Mechanistic models to estimate these parameters are necessary to perform integrated assessments of solid waste management alternatives using a life-cycle approach; however, models are only as good as their parameterization. This study presents operational waste collection data that can be used in life-cycle models for areas with similar collection systems, and provides illustrative results from a collection process model using operational data. Fuel use and times associated with various aspects of waste collection were obtained for vehicles collecting mixed residential (residual) waste, recyclables, and yard waste from single-family residences in selected municipalities. The total average fuel economy for similarly-sized diesel collection vehicles was 0.6-1.4 km/L (1.4–3.3 mpg (miles per gallon)) for residual waste and 0.8–1 km/L (1.9–2.4 mpg) for recyclables. For residual waste and recyclables collection stops, the average time to collect at each residence using automated collection was 11–12 s and 13–17 s, respectively. The average time between stops was 11–12 s and 10–13 for residuals and recyclables, respectively. A single yard waste route was observed, and all collection times were longer than those measured for either recycling or residual waste. Unload or tip times were obtained or measured at a landfill, transfer station, and material recovery facility (MRF). Average time to unload was 7–9 min at a MRF, 14–22 min at a landfill, and 11 min at a transfer station. Commercial and multi-family collection vehicles tend to have longer stops and spend more time between stops than single-family collection, and a larger portion of fuel is used while driving relative to single-family collection. Roll-off vehicles, which collect more waste per stop, spend longer at each stop and drive longer distances between stops than front-loader vehicles. Diesel roll-offs averaged 2.4 km/L (5.7 mpg) and front-loaders averaged 1.4 km/L (3.3 mpg).}, journal={Resources, Conservation and Recycling}, publisher={Elsevier BV}, author={Jaunich, Megan K. and Levis, James W. and DeCarolis, Joseph F. and Gaston, Eliana V. and Barlaz, Morton A. and Bartelt-Hunt, Shannon L. and Jones, Elizabeth G. and Hauser, Lauren and Jaikumar, Rohit}, year={2016}, month={Nov}, pages={92–102} }
 @article{jaunich_levis_barlaz_decarolis_2016, title={Lifecycle Process Model for Municipal Solid Waste Collection}, volume={142}, ISSN={0733-9372 1943-7870}, url={http://dx.doi.org/10.1061/(ASCE)EE.1943-7870.0001065}, DOI={10.1061/(ASCE)EE.1943-7870.0001065}, abstractNote={AbstractA process model was developed using a lifecycle approach to estimate the cost and energy use associated with municipal solid waste collection, which is the most fuel-intensive and often the most costly aspect of solid waste management. The model divides collection service areas into single-family residential, multi-family residential, and commercial sectors with sector-specific, user-defined characteristics, including population, waste generation, and waste composition. Waste is collected by a set of processes (e.g., residual waste, recyclables collection) defined by costs, collection activity parameters, and energy use. The model overpredicted fuel use by ~25% compared with data obtained from actual single-family residential collection routes and their average fuel efficiencies, but was within 10% when modal fuel efficiencies (e.g., driving, idling) were considered. Adding recyclables or yard waste collection to a mixed waste collection program increased fuel consumption by approximately 75% per ...}, number={8}, journal={Journal of Environmental Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Jaunich, Megan K. and Levis, James W. and Barlaz, Morton A. and DeCarolis, Joseph F.}, year={2016}, month={Aug}, pages={04016037} }
 @article{hodge_levis_decarolis_barlaz_2016, title={Systematic Evaluation of Industrial, Commercial, and Institutional Food Waste Management Strategies in the United States}, volume={50}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.6b00893}, DOI={10.1021/acs.est.6b00893}, abstractNote={New regulations and targets limiting the disposal of food waste have been recently enacted in numerous jurisdictions. This analysis evaluated selected environmental implications of food waste management policies using life-cycle assessment. Scenarios were developed to evaluate management alternatives applicable to the waste discarded at facilities where food waste is a large component of the waste (e.g., restaurants, grocery stores, and food processors). Options considered include anaerobic digestion (AD), aerobic composting, waste-to-energy combustion (WTE), and landfilling, and multiple performance levels were considered for each option. The global warming impact ranged from approximately -350 to -45 kg CO2e Mg(-1) of waste for scenarios using AD, -190 to 62 kg CO2e Mg(-1) for those using composting, -350 to -28 kg CO2e Mg(-1) when all waste was managed by WTE, and -260 to 260 kg CO2e Mg(-1) when all waste was landfilled. Landfill diversion was found to reduce emissions, and diverting food waste from WTE generally increased emissions. The analysis further found that when a 20 year GWP was used instead of a 100 year GWP, every scenario including WTE was preferable to every scenario including landfill. Jurisdictions seeking to enact food waste disposal regulations should consider regional factors and material properties before duplicating existing statutes.}, number={16}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Hodge, Keith L. and Levis, James W. and DeCarolis, Joseph F. and Barlaz, Morton A.}, year={2016}, month={Jul}, pages={8444–8452} }
 @article{pressley_levis_damgaard_barlaz_decarolis_2015, title={Analysis of material recovery facilities for use in life-cycle assessment}, volume={35}, ISSN={0956-053X}, url={http://dx.doi.org/10.1016/j.wasman.2014.09.012}, DOI={10.1016/j.wasman.2014.09.012}, abstractNote={Insights derived from life-cycle assessment of solid waste management strategies depend critically on assumptions, data, and modeling at the unit process level. Based on new primary data, a process model was developed to estimate the cost and energy use associated with material recovery facilities (MRFs), which are responsible for sorting recyclables into saleable streams and as such represent a key piece of recycling infrastructure. The model includes four modules, each with a different process flow, for separation of single-stream, dual-stream, pre-sorted recyclables, and mixed-waste. Each MRF type has a distinct combination of equipment and default input waste composition. Model results for total amortized costs from each MRF type ranged from $19.8 to $24.9 per Mg (1Mg=1 metric ton) of waste input. Electricity use ranged from 4.7 to 7.8kWh per Mg of waste input. In a single-stream MRF, equipment required for glass separation consumes 28% of total facility electricity consumption, while all other pieces of material recovery equipment consume less than 10% of total electricity. The dual-stream and mixed-waste MRFs have similar electricity consumption to a single-stream MRF. Glass separation contributes a much larger fraction of electricity consumption in a pre-sorted MRF, due to lower overall facility electricity consumption. Parametric analysis revealed that reducing separation efficiency for each piece of equipment by 25% altered total facility electricity consumption by less than 4% in each case. When model results were compared with actual data for an existing single-stream MRF, the model estimated the facility's electricity consumption within 2%. The results from this study can be integrated into LCAs of solid waste management with system boundaries that extend from the curb through final disposal.}, journal={Waste Management}, publisher={Elsevier BV}, author={Pressley, Phillip N. and Levis, James W. and Damgaard, Anders and Barlaz, Morton A. and DeCarolis, Joseph F.}, year={2015}, month={Jan}, pages={307–317} }
 @article{levis_barlaz_decarolis_ranjithan_2014, title={Systematic Exploration of Efficient Strategies to Manage Solid Waste in U.S. Municipalities: Perspectives from the Solid Waste Optimization Life-Cycle Framework (SWOLF)}, volume={48}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es500052h}, DOI={10.1021/es500052h}, abstractNote={Solid waste management (SWM) systems must proactively adapt to changing policy requirements, waste composition, and an evolving energy system to sustainably manage future solid waste. This study represents the first application of an optimizable dynamic life-cycle assessment framework capable of considering these future changes. The framework was used to draw insights by analyzing the SWM system of a hypothetical suburban U.S. city of 100 000 people over 30 years while considering changes to population, waste generation, and energy mix and costs. The SWM system included 3 waste generation sectors, 30 types of waste materials, and 9 processes for waste separation, treatment, and disposal. A business-as-usual scenario (BAU) was compared to three optimization scenarios that (1) minimized cost (Min Cost), (2) maximized diversion (Max Diversion), and (3) minimized greenhouse gas (GHG) emissions (Min GHG) from the system. The Min Cost scenario saved $7.2 million (12%) and reduced GHG emissions (3%) relative to the BAU scenario. Compared to the Max Diversion scenario, the Min GHG scenario cost approximately 27% less and more than doubled the net reduction in GHG emissions. The results illustrate how the timed-deployment of technologies in response to changes in waste composition and the energy system results in more efficient SWM system performance compared to what is possible from static analyses.}, number={7}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Levis, James W. and Barlaz, Morton A. and DeCarolis, Joseph F. and Ranjithan, S. Ranji}, year={2014}, month={Mar}, pages={3625–3631} }
 @article{levis_barlaz_decarolis_ranjithan_2013, title={A generalized multistage optimization modeling framework for life cycle assessment-based integrated solid waste management}, volume={50}, ISSN={1364-8152}, url={http://dx.doi.org/10.1016/j.envsoft.2013.08.007}, DOI={10.1016/j.envsoft.2013.08.007}, abstractNote={Solid waste management (SWM) is an integral component of civil infrastructure and the global economy, and is a growing concern due to increases in population, urbanization, and economic development. In 2011, 1.3 billion metric tons of municipal solid waste (MSW) were generated, and this is expected to grow to 2.2 billion metric tons by 2025. In the U.S., MSW systems processed approximately 250 million tons of waste and produced 118 Tg of CO2e emissions, which represents over 8% of non-energy related greenhouse gas (GHG) emissions, and 2% of total net GHG emissions. While previous research has applied environmental life cycle assessment (LCA) to SWM using formal search techniques, existing models are either not readily generalizable and scalable, or optimize only a single time period and do not consider changes likely to affect SWM over time, such as new policy and technology innovation. This paper presents the first life cycle-based framework to optimize—over multiple time stages—the collection and treatment of all waste materials from curb to final disposal by minimizing cost or environmental impacts while considering user-defined emissions and waste diversion constraints. In addition, the framework is designed to be responsive to future changes in energy and GHG prices. This framework considers the use of existing SWM infrastructure as well as the deployment and utilization of new infrastructure. Several scenarios, considering cost, diversion, and GHG emissions, are analyzed in a 3-stage test system. The results show the utility of the multi-stage framework and the insights that can be gained from using such a framework. The framework was also used to solve a larger SWM system; the results show that the framework solves in reasonable time using typical hardware and readily available mathematical programming solvers. The framework is intended to inform SWM by considering costs, environmental impacts, and policy constraints.}, journal={Environmental Modelling & Software}, publisher={Elsevier BV}, author={Levis, James W. and Barlaz, Morton A. and DeCarolis, Joseph F. and Ranjithan, S. Ranji}, year={2013}, month={Dec}, pages={51–65} }
 @article{levis_barlaz_2011, title={Is Biodegradability a Desirable Attribute for Discarded Solid Waste? Perspectives from a National Landfill Greenhouse Gas Inventory Model}, volume={45}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es200721s}, DOI={10.1021/es200721s}, abstractNote={There is increasing interest in the use of biodegradable materials because they are believed to be "greener". In a landfill, these materials degrade anaerobically to form methane and carbon dioxide. The fraction of the methane that is collected can be utilized as an energy source and the fraction of the biogenic carbon that does not decompose is stored in the landfill. A landfill life-cycle model was developed to represent the behavior of MSW components and new materials disposed in a landfill representative of the U.S. average with respect to gas collection and utilization over a range of environmental conditions (i.e., arid, moderate wet, and bioreactor). The behavior of materials that biodegrade at relatively fast (food waste), medium (biodegradable polymer) and slow (newsprint and office paper) rates was studied. Poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHBO) was selected as illustrative for an emerging biodegradable polymer. Global warming potentials (GWP) of 26, 720, -1000, 990, and 1300 kg CO(2)e wet Mg(-1) were estimated for MSW, food waste, newsprint, office paper, and PHBO, respectively in a national average landfill. In a state-of-the-art landfill with gas collection and electricity generation, GWP's of -250, 330, -1400, -96, and -420 kg CO(2)e wet Mg(-1) were estimated for MSW, food waste, newsprint, office paper and PHBO, respectively. Additional simulations showed that for a hypothetical material, a slower biodegradation rate and a lower extent of biodegradation improve the environmental performance of a material in a landfill representative of national average conditions.}, number={13}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Levis, James W. and Barlaz, Morton A.}, year={2011}, month={Jul}, pages={5470–5476} }
 @article{levis_barlaz_tayebali_ranjithan_2011, title={Quantifying the Greenhouse Gas Emission Reductions Associated with Recycling Hot Mix Asphalt}, volume={12}, ISSN={1468-0629 2164-7402}, url={http://dx.doi.org/10.1080/14680629.2011.9690352}, DOI={10.1080/14680629.2011.9690352}, abstractNote={ABSTRACT Market based policies to reduce greenhouse gas emissions have become increasingly popular in the last decade. These policies provide economic incentives for reducing greenhouse gas emissions. A life-cycle inventory model was developed to evaluate three alternatives for the management of waste hot mix asphalt (HMA) including, (1) recycling as new aggregate, (2) recycling as new HMA, and (3) disposal in a landfill. Global warming potential, environmental emissions, and total energy use were quantified for each management alternative. The recycling of used asphalt into new HMA results in a reduction of 16 kg CO2e compared to landfilling. Recycling used HMA as aggregate reduced GHG emissions by 9 kg CO2e A Monte Carlo analysis on the alternatives showed that the range of reduction for recycling as HMA was 12 to 26 kg CO2e and for recycling as aggregate 6 to 11 kg CO2e.}, number={1}, journal={Road Materials and Pavement Design}, publisher={Informa UK Limited}, author={Levis, James W. and Barlaz, Morton A. and Tayebali, Akhtar and Ranjithan, S. Ranji}, year={2011}, month={Jan}, pages={57–77} }
 @article{levis_barlaz_2011, title={What Is the Most Environmentally Beneficial Way to Treat Commercial Food Waste?}, volume={45}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es103556m}, DOI={10.1021/es103556m}, abstractNote={Commercial food waste represents a relatively available high-quality feedstock for landfill diversion to biological treatment. A life-cycle assessment was performed for commercial food waste processed through aerobic composting systems of varying complexity, anaerobic digestion, and landfills with and without gas collection and energy recovery, as well as a bioreactor landfill. The functional unit was 1000 kg of food waste plus 550 kg of branches that are used as a bulking agent. For each alternative, global warming potential, NO(x) and SO(2) emissions, and total net energy use were determined. Anaerobic digestion was the most environmentally beneficial treatment option, leading to -395 kg net CO(2)e per functional unit. This result was driven by avoided electricity generation and soil carbon storage from use of the resulting soil amendment. The composting alternatives led to between -148 and -64 kg net CO(2)e, whereas the landfill alternatives led to the emission of -240 to 1100 kg CO(2)e. A traditional landfill with energy recovery was predicted to have lower emissions than any of the composting alternatives when a fertilizer offset was used. There is variation in the results based on uncertainty in the inputs, and the relative rankings of the alternatives are dependent on the soil amendment offset that is used. The use of compost to offset peat has greater emission offsets than the value of compost as a fertilizer.}, number={17}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Levis, James W. and Barlaz, Morton A.}, year={2011}, month={Sep}, pages={7438–7444} }
 @article{levis_barlaz_themelis_ulloa_2010, title={Assessment of the state of food waste treatment in the United States and Canada}, volume={30}, ISSN={0956-053X}, url={http://dx.doi.org/10.1016/j.wasman.2010.01.031}, DOI={10.1016/j.wasman.2010.01.031}, abstractNote={Currently in the US, over 97% of food waste is estimated to be buried in landfills. There is nonetheless interest in strategies to divert this waste from landfills as evidenced by a number of programs and policies at the local and state levels, including collection programs for source separated organic wastes (SSO). The objective of this study was to characterize the state-of-the-practice of food waste treatment alternatives in the US and Canada. Site visits were conducted to aerobic composting and two anaerobic digestion facilities, in addition to meetings with officials that are responsible for program implementation and financing. The technology to produce useful products from either aerobic or anaerobic treatment of SSO is in place. However, there are a number of implementation issues that must be addressed, principally project economics and feedstock purity. Project economics varied by region based on landfill disposal fees. Feedstock purity can be obtained by enforcement of contaminant standards and/or manual or mechanical sorting of the feedstock prior to and after treatment. Future SSO diversion will be governed by economics and policy incentives, including landfill organics bans and climate change mitigation policies.}, number={8-9}, journal={Waste Management}, publisher={Elsevier BV}, author={Levis, J.W. and Barlaz, M.A. and Themelis, N.J. and Ulloa, P.}, year={2010}, month={Aug}, pages={1486–1494} }