ENS 201 Chapter 21, Spring 2008

Solid, Toxic and Hazardous Waste Chapter 21 Outline • Solid Waste: Sources/ types • Waste Disposal Methods  Open dumps  Sanitary landfills  Waste incineration • Shrinking the Waste Stream: Waste Reduction  Recycling, composting, demanufacturing… • Hazardous & Toxic Wastes  Hazardous Waste Management Options SOLID WASTE • Sources/types:  Agricultural waste- crop residues & animal manure  Mining, oil & gas production waste  Industrial Waste - Hazardous/Toxic  Municipal Waste –household & commercial refuse Composition of US Domestic Waste by % of total weight Plastics make up only 8% by weight, but up to 20% of total volume Waste Disposal Methods: Open Dumps • Open, unregulated dumps are still the predominant method of waste disposal in most developing countries • Most developed countries forbid open dumping, but illegal dumping is still a problem  E.g.: Waste motor oil poured into the sewers • Open dumps  Waste is left in giant piles exposed to the wind & rain, as well as rats, flies & other vermin  Least desirable waste disposal method • Ocean Dumping:  Bottles, cans, plastic containers, waste oil, sewage sludge….  Prohibited in developed countries Sanitary Landfills Sanitary Landfills are better options than open dumps Waste Disposal Methods: Landfills • Sanitary Landfills:  Refuse are compacted & covered daily with dirt  A waterproof lining (impermeable clay or plastic lining) is required to prevent leaching of chemicals (oil, chemicals, toxic metals…) into underground aquifers  Drainage systems are installed in & around the liner to catch drainage & to help monitor chemicals that may be leaking  Methane, or natural gas -a product of garbage decomposition in a landfill- can be recovered & used as an energy resource Topsoil Sand Clay Garbage Garbage Sand Synthetic liner Sand Clay Subsoil When landfill is full, layers of soil and clay seal in trash Methane storage and compressor building Electricity generator building Leachate treatment system Methane gas recovery Pipe collect explosive methane gas used as fuel to generate electricity Compacted solid waste Leachate storage tanks Leachate monitoring well Leachate monitoring well Groundwater Groundwater Groundwater monitoring well Groundwater monitoring well Leachate pipes Leachate pipes Leachate pumped up to storage tanks for safe disposal Leachate pumped up to storage tanks for safe disposal Clay and plastic lining to prevent leaks; pipes collect leachate from bottom of landfill Landfills siting • Siting of new landfills must be considered with attention  Sites with less leaky geological foundations are in favor of sites on highly permeable or faulted rock formation  Away from rivers, lakes, floodplains, & aquifer recharge zones Landfills Problems Historically, landfills have been a convenient & relatively inexpensive waste-disposal option • Current problems:  Rising land prices & shipping fees, & increasingly demanding landfill construction & maintenance requirements => - Landfilling a more expensive disposal method - Suitable landfill sites are becoming scarce  Increasingly, communities are rejecting new landfills  Old landfills are quickly reaching capacity & closing Advantages Disadvantages No open dumping Little odor Low groundwater pollution if sited properly Can be built quickly Low operating costs Can handle large amounts of waste Filled land can be used for other purposes No shortage of landfill space in many areas Noise and traffic Dust Air pollution from toxic gases and volatile organic compounds release greenhouse gases (methane and CO2) Groundwater contamination Slow decomposition of wastes Encourages waste production Eventually leaks and can contaminate groundwater Waste Disposal Methods: Exporting Waste Most industrialized nations have agreed to stop shipping hazardous & toxic waste to less-developed countries However The practice still continues • “Garbage imperialism” also operates in wealthier countries:  Poor neighborhoods & minority populations (e.g., Indian reservations) are much more likely than richer ones to be the recipients of dumps, waste incinerators & other locally unwanted land uses Waste Disposal Methods: Incineration & Resource Recovery Incinerators: Specially designed burning plants capable of burning thousands of tons of waste per day Mass Burn Incineration- Everything smaller than sofas and refrigerator is loaded into furnace • Advantages  Reduces disposal volume by 80-90%  Energy recovery- Heat derived from incinerated refuse is a useful resource; it can be used to produce steam used for heating buildings or generating electricity Drawbacks of Incineration • Initial construction costs are high • Refuse must be sorted to remove recyclable & unburnable materials before combustion • Creates air pollution problems • Incinerator ash (both fly ash & residual one) poses threat to environmental health  High levels of toxic material (such as dioxins, lead, cadmium, etc.): in fly ash more than residual one  Pollution control methods are not 100% effective  Residual ash must be disposed of properly Shrinking the Waste Stream: Recycling Producing less waste is better than struggling with disposal methods. Best strategy is the 3Rs one: Reduce, Reuse, Recycle. • Recycling: reprocessing of discarded materials into new, useful products  Some recycling reprocesses discarded materials for the same purposes - E.g.: aluminum cans & glass bottles are melted and recast into new ones  Other processes turn old material into entirely new products - Old tire  road surfacing - News paper  cellulose insulation - Kitchen waste  soil amendment - Steel cans  automobiles and construction material US Recycling Rates Potential Problems of Recycling • Market prices fluctuation  E.g.: Newsprint: $160/ton in 1995  $42/ton in 2000 • Contamination  Billions of PET plastic soft drink bottles  many items (carpet, plastic packaging…) But  A single PVC bottle can ruin an entire truckload of PET if melted together Benefits of Recycling Recycling is a much better alternative than burning or dumping wastes • Saves money, energy, raw materials & land space Pickup of recyclable: $40/ton Disposal in landfill: $80/ton • Encourages individual awareness & responsibility for the refuse produced  Japan has the most successful recycling program: - 50% of all wastes are recycled - Japanese families separate wastes into 7 categories! • Cuts waste volumes drastically & reduces pressure on disposal systems Benefits of Recycling • Reduces demand for raw resources, energy consumption & air pollution  Recycling the print run of a single day issue of New York Times would spare 75000 trees!!!  Recycling 1 ton of aluminum: - Saves 4 tons of bauxite (aluminum ore) - Saves ~ 1 ton of petroleum - Keep out 35 kg of aluminum fluoride out of the air • Reduces litter from roadsides, rivers, oceans…  E.g.: In US each piece of litter picked up by crews costs 32 cents Shrinking the Waste Stream: Composting  Biological degradation of organic material such as yard or kitchen waste under aerobic conditions - The organic compost  nutrient-rich soil amendment that  Helps water retention  Slows soil erosion  Improves crop yields  A home compost pile is an easy environmentally friendly way to dispose of organic wastes  To be successful, a community composting program must: - Overcome siting problems - Control odors - Exclude toxic materials that can contaminate the compost & make it unsuitable for use as a fertilizer on crops & lawns Shrinking the Waste Stream • Demanufacturing  Disassembly & recycling of obsolete consumer products, such as TV sets, personal computers, refrigerators, washing machines, & air conditioners • Reuse  Cleaning & reusing materials in their present form - Saves the cost & energy of remaking them into something else - Auto parts are regularly sold from junkyards - Glass & plastic bottles are routinely returned to beverage producers for washing & refilling Shrinking the Waste Stream • Producing Less Waste  Excess packaging of food & consumer products is one of our greatest sources of unnecessary waste - Paper, plastic, glass, & metal packaging material make up 50% of domestic trash by volume - The use of photodegradable & biodegradable plastics can reduce the volume of wastes but leaves toxic residues in the environment  Too much emphasis on recycling ? - Recycling is actually the third “R” in the waste hierarchy. The two preferred methods are reduction & reuse Much of packaging is for marketing and has little to do with product protection Hazardous Waste • Legally, hazardous waste is any discarded liquid or solid that contains substances known to be:  Fatal to humans or laboratory animals in low doses  Toxic, carcinogenic, mutagenic, or teratogenic to humans or other life-forms  Ignitable with a flash point less than 60o C  Explosive or highly reactive Toxic and hazardous wastes must be tracked Hazardous Waste Management Options • Produce Less Waste  Avoid creating wastes in the first place  Recycle and Reuse • Convert to Less Hazardous Substances  Physical Treatment (Isolation of toxic substances)  Incineration  Chemical Processing (Transformation)  Bioremediation (Microorganisms) Hazardous Waste Management Options Inevitably there will be some material that cannot be destroyed, transformed, or caused to vanish  Store Permanently  Retrievable Storage - Can be inspected and periodically retrieved  Secure Landfills - Modern, complex landfills with multiple liners and other impervious layers and monitoring systems Secure Landfills