Determining economically optimal household organic material management pathways

Abstract

This article presents a model to determine profit-maximizing processing pathways for urban household organic material. It was applied to a case study system in the city of Rochester, NY to compare the profitability of local material management pathways. Four industrially relevant and locally available pathways were examined: anaerobic digestion (AD), simultaneous saccharification and fermentation (SSF), windrow composting, and landfill with gas capture. This research hypothesized that the current status quo of landfill with gas capture is profit-maximizing, and formulated objective functions based on alternate practices of AD, SSF, and windrow composting to test the status quo. Material chemical parameters such as biomethane potential and carbon to nitrogen ratio were experimentally determined and used as inputs. The baseline model showed the status quo of landfill with gas capture is 52–92% less profitable than optimal pathways depending on ranges of input parameters. Optimal pathways were AD for single-stream and food, composting for compostable paper, and SSF for yard trimmings. Composting was the most sensitive pathway to market and chemical variables. AD being the optimal pathway is robust for food waste compared to landfill with gas capture; to reach parity with AD, landfill tipping fees must double or AD trucking costs triple.