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1、Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Enger & SmithEnvironmental ScienceA Study of InterrelationshipsThirteenth EditionChapter 17Solid Waste Management and DisposalSolid Waste Management and DisposalOutline17.1 Kinds of Solid Waste17.2 Municipal So
2、lid Waste17.3 Methods of Waste Disposal 17.1 Kinds of Solid WasteSolid waste is generally made of objects or particles that accumulate on the site where they are produced.They are typically categorized by the sector of the economy responsible for producing them.17.1 Kinds of Solid WasteMining wastes
3、 are generated in three ways:Waste material is left on the surface.Milling tailings are dumped on the land or stored in ponds.Waste or tailings drainage often contains hazardous materials.Agricultural wasteIncludes waste from raising animals as well as crop and tree harvesting.90% is used as fertili
4、zer or other forms of soil enhancement.17.1 Kinds of Solid WasteIndustrial solid waste consists of solid waste other than mining.Estimated to be between 200-600 million metric tons annually.Demolition wasteSludgeCombustion ashMunicipal solid waste consists of all the materials people in a region no
5、longer want.210 million metric tons annually.17.2 Municipal Solid WasteIn modern society, many products are discarded when they are broken or worn out, while others only have a temporary use.Those that have only temporary uses make up the majority of solid waste.17.2 Municipal Solid WasteThe Unites
6、States produces about 210 million metric tons of municipal solid waste annually.This equates to 2 kg of trash per person per day.Per capita waste has increased 70% since 1960.17.2 Municipal Solid WasteMunicipal solid waste generation rates17.2 Municipal Solid WasteNations with a higher standard of l
7、iving tend to produce more municipal solid waste per person than less-developed countries.Large metropolitan areas have the greatest difficulty dealing with solid waste.17.2 Municipal Solid WasteWaste generation and lifestyle17.3 Methods of Waste DisposalIn the past, the favored means of waste dispo
8、sal was to dump solid wastes outside of city or village limits.To minimize the volume of waste, the dump was often burned.This practice is still employed in remote or sparsely populated areas in the world.17.3 Methods of Waste DisposalFive techniques are now used in waste disposal:LandfillsIncinerat
9、ionSource reductionCompostingRecycling17.3 Methods of Waste DisposalLandfillsA municipal solid waste landfill is typically constructed above an impermeable clay layer, lined with an impermeable membrane.It includes mechanisms for dealing with liquid and gas materials generated by the contents of the
10、 landfill.Traditionally this has been the primary method of waste disposal.Cheap and convenientProblems associated with poorly designed landfills have been recognized, and substantial efforts are made to reduce the amount of waste entering landfills.17.3 Methods of Waste DisposalNew landfills have c
11、omplex bottom layers to trap contaminant-laden leachate.Monitoring systems are necessary to detect methane gas production and groundwater contamination.In some cases, methane is collected and used to generate electricity.New landfills currently cost up to $1 million per hectare to prepare.17.3 Metho
12、ds of Waste DisposalA well-designed modern landfill17.3 Methods of Waste DisposalThe number of landfills is declining.Many small landfills that were not meeting regulations have been closed.Capacity has been reached.New landfills often resisted due to public concerns over groundwater contamination,
13、odors, rodents, and truck traffic.17.3 Methods of Waste DisposalReducing the number of landfills17.3 Methods of Waste DisposalIncineration is the process of burning refuse in a controlled manner.Currently, about 15% of U.S. municipal solid waste is incinerated.Most incinerators are designed to captu
14、re heat, which is then used to make steam to produce electricity.The production of electricity partially offsets disposal costs.Most incinerators burn unprocessed municipal solid waste. This process is referred to as mass burn technology.17.3 Methods of Waste DisposalIncinerators drastically reduce
15、the amount of municipal solid waste.Up to 90% by volume and 75% by weight.Primary risks of incineration involve air quality problems and toxicity and disposal of ash.Toxic substances are more concentrated in ash.17.3 Methods of Waste DisposalEven with modern pollution controls, small amounts of poll
16、utants are still released into environment.The cost of land and construction for new incinerators are also major concerns facing many communities.17.3 Methods of Waste DisposalU.S. EPA has not looked favorably on construction of new waste-to-energy facilities.It has encouraged recycling and source r
17、eduction as more effective solutions to deal with solid waste.17.3 Methods of Waste DisposalDisposal methods used in various countries17.3 Methods of Waste DisposalMulch is organic material used to protect areas where the soil is disturbed, or to control growth of unwanted vegetation.Organic materia
18、ls such as large branches and bark are chopped or shredded into smaller pieces.17.3 Methods of Waste DisposalComposting is using natural decomposition to transform organic material into compost, a humus-like product with many environmental benefits.With proper management of air and water, composting
19、 can transform large quantities of organic material into compost over a short period of time.Small-scale composting can be accomplished in the backyard, mixing green materials (grass clippings, vegetable scraps, etc.) and brown materials (dry leaves, twigs, soiled paper towels).17.3 Methods of Waste
20、 DisposalAbout 3,800 composting facilities are currently in use in the United States.Most municipal programs involve one of three composting methods:Window systemsAerated pilesEnclosed vessels17.3 Methods of Waste DisposalThe simplest way to reduce waste is to prevent it from ever becoming waste in
21、the first place.Source reduction is the practice of designing, manufacturing, purchasing, using and reusing materials so that the amount of waste or its toxicity is reduced.17.3 Methods of Waste DisposalDesign changesSince the 2-liter soft drink bottle was introduced in 1977, weight has been reduced
22、 by 25%.As a result, 250 million pounds of plastic have been kept out of the waste stream.Manufacturing processes reduce waste and increase efficiency.Purchasing decisionsChoose reduced packaging and plan quantities accordingly.17.3 Methods of Waste DisposalUsing materials to avoid waste generationR
23、educe use of hazardous materials.Follow label directions carefully and use the smallest amount necessary.Reusing itemsDelay or prevent entry of items into waste collection stream.17.3 Methods of Waste DisposalMost businesses and manufacturers have a strong economic incentive to ensure they get the m
24、ost from all materials they use.Any activities that reduce the amount of waste produced, reduce the:Cost of waste disposalAmount of raw materials neededAmount of pollution generated17.3 Methods of Waste DisposalRecycling is one of the best environmental success stories of the late 20th century.In th
25、e United States, recycling (including composting) diverted about 30% of solid waste stream from landfills and incinerators in 2007.Benefits:Resource conservationPollution reductionEnergy savingsJob creationLess need for landfills and incinerators17.3 Methods of Waste DisposalRecycling percentage for
26、 selected materials (2007) and recycling rates from 1960-2007.17.3 Methods of Waste DisposalContainer laws provide an economic incentive to recycle.Requires a deposit on all reusable beverage containers.A national “bottle bill” would reduce litter, save energy and money, create jobs, and help conser
27、ve natural resources.Mandatory recycling laws provide a statutory incentive to recycle.17.3 Methods of Waste DisposalCurbside recycling provides a convenient way for people to recycle.In 1990, 1,000 U.S. cities had curbside recycling programs.In 2009, 11,100 cities had curbside recycling programs.Ci
28、ties with curbside recycling tend to have higher recycling rates than cities that lack such programs.17.3 Methods of Waste DisposalThere are many technical and economic problems associated with recycling.Plastics are recyclable, but technology differs from plastic to plastic.Milk containers tend to
29、be high-density polyethylene (HDPE), while egg containers are polystyrene (PS), and soft-drink bottles are polyethylene terephthalate (PET).17.3 Methods of Waste DisposalIncreasing amounts of plastic in trash17.3 Methods of Waste DisposalThe plastics industry is researching new technologies.Economic
30、s of recycling are of concern. Unless demand for products keeps pace with growing supply, recycling programs will face an uncertain future.17.3 Methods of Waste DisposalThe long-term success of recycling programs is tied to other economic incentives such as taxing issues, and the development of and
31、demand for products manufactured from recycled materials.Government subsidies artificially lower cost of virgin forest materials compared to recycled materials.Demand for recycled products must grow if recycling is to succeed on a large scale.17.3 Methods of Waste DisposalRecycling composite pricesS
32、ummaryMunicipal solid waste is managed by landfills, incineration, composting, waste reduction, and recycling.The most fundamental way to reduce waste is to prevent it from ever becoming waste in the first place.About 30% of the waste generated in North America is handled through recycling.SummaryFuture management of municipal solid waste will be an integrated approach involving landfills, incineration, composting, source reduction, and recycling.The degree to which any option will be used depends on economics, changes in technology, and citizen awareness and involvement.
