Optimal strategies for sustainable household organic material management in the city of Rochester, NY

Abstract

The purpose of this research was to explore the benefits and challenges of implementing a sustainable system for managing household organic material (HHOM) in the city of Rochester, NY. Elsewhere in the United States and the world, HHOM (i.e. excess food, yard matter, and compostable paper) has been increasingly diverted from landfills to organic waste-to-energy and composting pathways (European Environment Agency 2013a; Skumatz and Freeman 2006). Landfill diversion is enabled by municipal projects that support source separation of HHOM out of the municipal solid waste (MSW) stream, thereby extracting valuable organic resources for higher-value processing (NYSDEC 2010). This has been done to increase the profitability of HHOM management (Eriksson et al. 2005) while simultaneously achieving benefits to the environment (e.g. life-cycle greenhouse gas reductions) (Ebner et al., 2014; Sanscartier et al. 2012; Environmental Protection Agency 2013c) and society (e.g. community resilience; food security; local agriculture) (Sundkvist et al. 2001; Curtis 2003; Jansson 2013; Colding and Barthel 2013). In recent years, only 10% of the 27,000 Metric Tons (MT) of HHOM in the city of Rochester has been diverted from landfills (NYSDEC 2008). It was hypothesized in this research that an effectively planned and implemented municipal project designed to increase processing of HHOM in organic waste-to-energy or composting pathways would sustainably bolster economic, social, and environmental assets in the city of Rochester, NY. The first step in testing this assertion involved gathering data on the social sustainability of a project utilizing source separated HHOM. Surveys and interviews of potential project participants in the Southeast section of the city of Rochester, NY were conducted to examine residents\u27 a) likelihood of project participation, b) economic incentives to reduce MSW generation and HHOM 4 source separation, c) current HHOM management behaviors, and d) awareness of available HHOM management pathways. Resident survey and interview responses indicated that residents are likely to reduce MSW generation and to participate in curbside collection of source separated HHOM, as long as these goals are incentivized. In addition, composting was found to be the most well-known pathway for HHOM management. Additional education is required to increase awareness of the other pathways for managing HHOM, yet residents indicated that they are interested in purchasing pathway products (i.e. locally produced energy and compost). The survey and interview data indicated a need for incentivizing sustainable HHOM management behaviors. Thus, it was essential to determine the most cost-effective municipal project to drive source separation of HHOM. A literature review was conducted of projects in locales achieving high landfill diversion of HHOM to identify the best policy options. The findings indicated that the ideal project to support source separation of HHOM in Rochester, NY is weight-based MSW pricing (also known as pay-as-you-throw) with free organic collection. The financial impacts of implementing a pay-as-you-throw (PAYT) project in the city of Rochester, NY were analyzed using a cost-benefit analysis (CBA). Development of the CBA model addressed the uncertainty in the financial impacts of implementing the PAYT project by conducting the analysis for multiple scenarios of key parameters such as actual resident HHOM source separation and MSW reduction behaviors. Data required to build scenarios was based on documented source separation and MSW generation performance for new and established PAYT projects. For each scenario, optimal MSW prices were found where municipal budget was maximized without reducing the average household budget. Then, project net present value was calculated. Weight-based PAYT project net present value (NPV) to the municipal solid waste collection budget for the City of Rochester Department of Environmental Services was calculated. The project NPV is between $12,100,000 and$18,100,000, with a projected increase in average city household budget over the 11 year project life. The project was shown to have annual positive net cash flows between $1,300,000 under a conservative MSW source reduction scenario and$2,100,000 with an optimistic source reduction scenario. At current City of Rochester solid waste collection budget levels of $17,300,000, the project would reduce annual expenditures by 8The surveys, interviews, and CBA showed the promise of implementing a project to utilize source separated HHOM. However, it remained unclear what local pathways were economically optimal (i.e. profit-maximizing) for processing excess food, compostable paper, and yard trimming feedstocks from households in the city of Rochester, NY. The product yields, costs, and revenues are 5 different for HHOM processing pathways, and can depend on the chemical properties of feedstocks. Due to these uncertainties, investment in sustainable HHOM infrastructure could be stymied unless the most profitable HHOM management pathways are identified. This was investigated by creating an engineering-economic model using the What\u27sBEST! Add-in for Microsoft Excel. The model looked at four management pathways for source separated HHOM: landfills with gas capture (i.e. status quo for Rochester, NY), plus anaerobic digestion (AD), simultaneous saccharification and fermentation (SSF), and windrow composting. Model indicators included pathway revenues (e.g. product sales and tipping fees), pathway costs (e.g. trucking, capital, operations), as well as feedstock chemical parameters. Empirical data was collected for biomethane potential (mL CH4 /g volatile solids) of representative HH food and compostable paper material using gas chromatography. Baseline results indicate that$3,000,000 in profit can be made from HHOM with profit-maximizing processing pathways. In the baseline, anaerobic digestion was optimal for food, SSF was optimal for yard trimmings, and composting was optimal for compostable paper. Landfills with gas capture were not economically optimal for the HHOM feedstocks. In the case of a single-stream HHOM collection scheme, the baseline model shows that anaerobic digestion is the most profitable pathway. Sensitivity analysis showed that product revenues were the primary drivers of profitability among profit-maximizing HHOM pathways. On the other hand, pathway tipping fees and feedstock trucking costs have a relatively minimal impact on profits. This research showed that updating HHOM management policy and practice in the city of Rochester, NY will maximize local environmental, social, and economic performance. This can and should be achieved with the expansion of AD, composting, and SSF infrastructure in place of landfills with gas capture