Masters Thesis

Feasibility study for Vashon Island composting facility

This master’s project investigates the feasibility of establishing a composting facility for greenwaste diversion on Vashon Island, WA. The composting facility would serve to compliment waste reduction efforts already in place on the island. The benefits from this project would include reducing greenhouse gas emissions, costs savings and creating a local product. I conducted a survey of the public schools and local restaurants to determine potential feedstock for the composting facility. In addition to the survey, results from a statewide waste characterization study were used as a guide for estimating the potential greenwaste available from residential households. The analysis indicates that approximately 3,100 tons of greenwaste are potentially available for diversion annually, largely from residential and landscaping debris sources. The survey results suggest that there is little interest in participating in a composting project by schools and restaurants, but that these organizations do not generate significant quantities of divertable greenwaste. Overall $25,620 could be saved in annual ferry and fuel expenses if 100% of the food waste and green debris currently going to the landfill were diverted to an on island composting facility. This number is likely to increase in time as nearby landfill options decrease and waste hauling costs increase. Currently, King County is reviewing the results from their island wide survey administered last spring to island residents regarding interest in a residential curbside pickup program for greenwaste. Once the results have been considered, King County will offer a public comment event on Vashon to hear directly from the citizenry. The analysis in this master’s project will inform the decision making process; it suggests that greenwaste diversion may be feasible provided that residential greenwaste diversion rates are sufficiently high and the facility can be constructed at the existing transfer station at a reasonable cost.