About Solid Waste
As we live our lives, leftovers build up. What doesn't go into the sewer system we call solid waste. Solid waste is divided into several categories based on what it is and how it is handled and regulated:
- Municipal Solid Waste (MSW) - includes all the garbage, yard waste and recyclables that residents and businesses set out for collection or haul to a City Recycling and Disposal station. It includes some materials and items that need special handling, such as old refrigerators and tires.
- Construction and Demolition Debris (C&D) - includes materials from construction and demolition activities such as wood, asphalt shingles, concrete, metal, rocks, brick, and drywall.
- Moderate Risk Wastes (MRW) - hazardous or toxic chemicals exempt from State hazardous waste regulation because they come from home uses or in specified small quantities from businesses, institutions, government agencies, and others. MRW includes used motor oil, pesticides, antifreeze, paint, and solvents. When households generate MRW, it's called Household Hazardous Waste (HHW). When businesses and others generate MRW, it's called Small Quantity Generator Waste (SQGW).
Biomedical waste is managed by the Seattle-King County Department of Public Health.
Using Spreadsheet Models for Estimating Collection Costs (pdf)
This 1999 paper details Seattle's journey from crisis to an international reputation as a leader in municipal recycling.
The Role of Full Cost Accounting in Solid Waste Management (pdf)
This paper describes two spreadsheet models developed by Seattle Public Utilities (SPU) to estimate collection costs. The models consider variations in collection frequency, truck types, material separation requirements, transfer points, and more for single-family, multi-family and commercial customers.
Who's making all this waste?
Almost one-half of all waste is collected from businesses and nearly a third is collected from single-family residences. Residents of multi-family buildings generate less than a tenth of all Seattle's waste. The remaining waste comes from self-haulers (residents and businesses who bring wastes directly to transfer stations).
Looking at just residential waste, in 1995 single-family households (70% of the population) generated 74% of all residential waste, while multi-family households (30% of the population) generated 26% of all residential waste. These proportions have changed very little since 1988. But in the future, as the population of multi-family housing increases, we can expect waste from that sector to increase proportionately.
How much is recycled or put in a landfill?
Of the 765,000 tons of waste generated in 1995, 19,000 tons were composted or grasscycled in people's yards, and 330,000 tons were recycled or composted through collection programs, recycling drives and drop-off programs.
The remaining 426,000 tons were hauled to a landfill in Eastern Oregon. This gives an overall recycling rate of 44% (percentage of total tons generated that is recycled). Considering residential waste only, however, 50% of this waste is recycled. Self-haulers recycle only 18% of their waste, due to the lack of recycling opportunities at the transfer station, and the effort it takes to separate materials for recycling with little or no financial payback.
What's in the garbage?
The composition of garbage that goes to the landfill changed dramatically in 1988 when city-wide curbside recycling and yardwaste collection programs were started. Despite participation in curbside recycling by nearly 90% of the one-to-four-plexes, and by 55% of apartment units, the garbage still contains many tons of materials that can be recycled. By far the greatest tonnage of recyclables still in the garbage is paper products - newspaper, cardboard and mixed paper- nearly 87,000 tons together in 1995. This is 20% of the total waste stream that goes to the landfill!
Seattle routinely conducts "waste sorts", which are statistical programs of sampling, sorting and weighing of waste, by twenty categories.
Construction and Demolition Debris
A sizable portion of the City's waste consists of construction and demolition (C&D) debris. Historically, most C&D debris has been disposed of separately, although some construction waste materials are disposed of as MSW. C&D is separated because the requirements for landfilling this "inert" material are less stringent than for garbage. C&D is increasingly being recycled. Of the C&D debris handled by the City in 1995:
- About 67,000 tons were disposed of as residential, commercial, or self-haul garbage.
- Another 119,500 tons were taken to the city's two privately-operated transfer stations, where C&D waste is accepted for a lower tip fee. The most common materials in C&D waste are painted or stained wood (7.5%), composition shingles (6.4%), mixed/demolition drywall (6%), new drywall (4.1%), and new lumber (3.8%). Of all the disposed C&D materials, approximately 40% is potentially recyclable.
An unknown quantity was separated on the job site and hauled to local facilities that accept separated wood, gypsum, metals, and other construction materials for recycling.
Moderate Risk Waste
Seattle generates an estimated 2,500 tons of Household Hazardous Waste (HHW) each year. The Washington State Department of Ecology estimates that over 50% of HHW is used motor oil. Other major hazard categories include: flammable liquids like fuels, solvents, and oil-based paint, yard and garden products like pesticides and herbicides, acids and caustics like household cleansers and hobby chemicals, antifreeze, and batteries.
420 tons of HHW was disposed of at City Household Hazardous Waste Collection Sites in 1999. In addition, 100 tons of used motor oil, one ton of oil filters, and 78 tons of vehicle batteries were brought to the City Recycling and Disposal stations for recycling in 1999. Local auto service companies and gas stations collect even more used oil.
Biomedical waste
Biomedical waste from medical, dental, and veterinary offices and hospitals is regulated by the State and King County health code. It must be collected and disposed by regulated companies. "Sharps" (hypodermic needles) are a type of biomedical waste that is accepted for proper disposal at City Recycling and Disposal Stations and at some pharmacies and doctors' offices. Read more about Sharps Disposal.
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