Chapter 18 - SOLID WASTE MANAGEMENT AND DISPOSAL

Sources of Solid Waste

• 755 mining & oil/gas production - left near mine sites
• 13% agriculture
• 9.5% industry - buried or incinerated
• 1.5% municipal
• 1% sewage sludge

Municipal Solid Waste

• An ever increasing problems
• US with 4.7% world's population produces 33% of the solid waste (196 m tons solid waste a year)
• Each person produces 1.5 kg trash a day (700 kg/yr)
• Volume of solid waste has increased 80% since 1960
• Volume will increase 20% by 2000

METHODS OF WASTE DISPOSAL

Landfilling (80% of municipal waste)

• Sanitary landfills, typically clay-lined depressions
• Garbage is covered with thin soil layer daily
• Modern site selection based on groundwater geology, soil type
• Since 1993 EPA requirements are an impermeable bottom layer (several layers clay, thick plastic, sand)
• Liner collects leachate or rainwater contaminated as it percolates down
• Leachate is monitored and/or collected by wells, pumped and stored in tanks or sent to a treatment plant
• Filled landfills are completely covered by clay, sand, gravel and soil then monitored by wells to detect any leakage into groundwater
• Methane gas produced collected or burned to produce steam/electricity

Landfilling Benefits

• Reduced odor, rodents, pests
• Low operating costs, handles large amounts of waste
• Put into operation quickly
• Landscaped aesthetically for recreation after use

Landfilling Disadvantages

• Traffic, noise, dust
• Emit toxic gases (H₂S, methane, organic gases)
• Contamination of groundwater

Incineration (17% is incinerated)

• Trash-to-energy incineration; trash burned as fuel for steam/electricity
• Most incinerators use unprocessed solid waste, not efficient
• Some use refuse-derived fuel; processed into pellets before combustion
• Only 90% removal of potential air pollutants
• 140 operators in US in 1993

Incineration Benefits

• Incineration kills germs and reduces amount of solid waste to landfills
• Energy is produced
• Electrostatic precipitators, scrubbers, filters reduce air pollution

Incineration Disadvantages

• Pollutants are released to atmosphere
• Ash produced can contain small amounts of toxic heavy metals
• Cost ($30-200 m) and siting are of major concern to communities

Methods of Solid Waste Disposal

• Waste management - a throwaway or high waste approach encouraging waste production
• Pollution prevention - a low waste approach using waste as resources

Pollution Prevention and Source Reduction

• 17% MSW recycled or composted
• Use less materials in making products
• Conversion from heavy packaging to lighter ones
• Making consumer products in concentrated forms
• Making products that last longer
• Using reusable containers - refillable glass bottles are 11% of market

Recycling (10% of waste)

• Conserves resources; goal is for 25% recycling by 2000
• Primary recycling (closed loop) recycles products to produce new products of the same type
• Secondary recycling (open loop) with waste producing different products
• High technology materials recovery facilities (MFR's) shred and automatically separate mixed urban waste
• Recover glass, aluminum iron, paper for sale
• Recycle or burn remaining waste for heat, electricity
• 220 MFR's in US by 1993
• Expensive to build and maintain
• Low technology recovery uses homes, businesses to separate waste
• Collection by municipalities or contractors for resale

Recycling Concerns

• Technology for recycling differs with different plastics
• Mike containers may be high density polyethylene (HDPR), egg containers may be polystyrene (PS), soft drink (PET)
• Economics also problematical; supply/demand

Municipal Composting

• Could cut US solid waste by 18%
• Compost is humus rich in organic matter and soil nutrients
• Biodegradable solid waste from slaughterhouses, food-processing plants, kitchen and yard waste and manure from feed lots can produce compost
• Can be produced in large plants or household bins

Municipal Composting Concerns

• Odors from composting facilities
• Cost compared to landfills

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