Environmental Science A Study of Interrelationships Twelfth Edition

Environmental Science A Study of Interrelationships Twelfth Edition Enger & Smith Chapter 17 Solid Waste Management and Disposal Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

Solid Waste Management and Disposal

Outline § Kinds of Solid Waste § Municipal Solid Waste § Methods of Waste Disposal

Kinds of Solid Waste § Solid 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.

Kinds of Solid Waste § Mining wastes 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 waste • Includes waste from raising animals as well as crop and tree harvesting. – 90% is used as fertilizer or other forms of soil enhancement.

Kinds of Solid Waste § Industrial solid waste consists of solid waste other than mining. • Estimated to be between 200 -600 million metric tons annually. – Demolition waste – Sludge – Combustion ash § Municipal solid waste consists of all the materials people in a region no longer want. – 210 million metric tons annually.

Municipal Solid Waste § In 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.

Municipal Solid Waste § The Unites States produces about 210 million metric tons of municipal solid waste annually. • This equates to 2 kg (4. 4 lbs) of trash person per day. – Per capita waste has increased 70% since 1960.

Municipal Solid Waste Municipal solid waste generation rates

Municipal Solid Waste § Nations with a higher standard of living tend to produce more municipal solid waste person than less-developed countries. § Large metropolitan areas have the greatest difficulty dealing with solid waste.

Municipal Solid Waste generation and lifestyle

Methods of Waste Disposal § In the past, the favored means of waste disposal 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.

Methods of Waste Disposal § Five techniques are now used in waste disposal: • • • Landfills Incineration Source reduction Composting Recycling

Methods of Waste Disposal § Landfills • A 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 landfill. • Traditionally this has been the primary method of waste disposal. – Cheap and convenient • Problems associated with poorly designed landfills have been recognized, and substantial efforts are made to reduce the amount of waste entering landfills.

Methods of Waste Disposal § New landfills have complex 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.

Methods of Waste Disposal A well-designed modern landfill

Methods of Waste Disposal § The 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, odors, rodents, and truck traffic. • Politicians are often unwilling to take strong positions that might alienate constituents.

Methods of Waste Disposal Reducing the number of landfills

Methods of Waste Disposal § Incineration 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 capture 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.

Methods of Waste Disposal § Incinerators drastically reduce 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.

Methods of Waste Disposal § Even with modern pollution controls, small amounts of pollutants are still released into environment. § The cost of land construction for new incinerators are also major concerns facing many communities. § Construction costs in North America in 2000 ranged from $45 -$350 million.

Methods of Waste Disposal § U. S. EPA has not looked favorably on construction of new waste-to-energy facilities. § It has encouraged recycling and source reduction as more effective solutions to deal with solid waste.

Methods of Waste Disposal methods used in various countries

Methods of Waste Disposal § Mulch is organic material used to protect areas where the soil is disturbed, or to control growth of unwanted vegetation. § Organic materials such as large branches and bark are chopped or shredded into smaller pieces.

Methods of Waste Disposal § Composting 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 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).

Methods of Waste Disposal Diverting waste through composting

Methods of Waste Disposal § About 3, 800 composting facilities are currently in use in the United States. § Most municipal programs involve one of three composting methods: • Windrow systems • Aerated piles • Enclosed vessels

Methods of Waste Disposal § The simplest way to reduce waste is to prevent it from ever becoming waste in 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.

Methods of Waste Disposal § Design changes • Since the 2 -liter soft drink bottle was introduced in 1977, weight has been reduced 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 decisions • Choose reduced packaging and plan quantities accordingly.

Methods of Waste Disposal § Using materials to avoid waste generation • Reduce use of hazardous materials. • Follow label directions carefully and use the smallest amount necessary. § Reusing items • Delay or prevent entry of items into waste collection stream.

Methods of Waste Disposal § Most businesses and manufacturers have a strong economic incentive to ensure they get the most from all materials they use. • Any activities that reduce the amount of waste produced, reduce the: – Cost of waste disposal – Amount of raw materials needed – Amount of pollution generated

Methods of Waste Disposal § Recycling is one of the best environmental success stories of the late 20 th century. § In the United States, recycling (including composting) diverted about 30% of solid waste stream from landfills and incinerators in 2007. • Benefits: – Resource conservation – Pollution reduction – Energy savings – Job creation – Less need for landfills and incinerators

Methods of Waste Disposal Recycling percentage for selected materials (2007) and recycling rates from 1960 -2007.

Methods of Waste Disposal § Container 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 conserve natural resources. § Mandatory recycling laws provide a statutory incentive to recycle.

Methods of Waste Disposal § Curbside recycling provides a convenient way for people to recycle. • In 1990, 1, 000 U. S. cities had curbside recycling programs. • In 2008, 11, 000 cities had curbside recycling programs. • Cities with curbside recycling tend to have higher recycling rates than cities that lack such programs.

Methods of Waste Disposal § In the U. S. , curbside pick-up of recyclables is increasingly the norm, but rates remain low. § Recycle Bank was founded in 2004. • Families on a garbage route are issued a container with a computer chip. Recyclables are weighed and the family earns points redeemable at merchants like CVS pharmacy. • Recycle Bank launched in Philadelphia in 2006. – Recycle rates rose from 7% to 90%. • In 2008 Recycle Bank started a pilot program in N. Y at Columbia University. – Students recycle and claim their points.

Methods of Waste Disposal § There are many technical and economic problems associated with recycling. • Plastics are recyclable, but technology differs from plastic to plastic. – Milk containers tend to be high-density polyethylene (HDPE), while egg containers are polystyrene (PS), and soft-drink bottles are polyethylene terephthalate (PET).

Methods of Waste Disposal Increasing amounts of plastic in trash

Methods of Waste Disposal § The plastics industry is researching new technologies. § Economics of recycling are of concern. • Unless demand for products keeps pace with growing supply, recycling programs will face an uncertain future.

Methods of Waste Disposal § The long-term success of recycling programs is tied to other economic incentives such as taxing issues, and the development of and 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.

Methods of Waste Disposal Recycling composite prices

Summary § Municipal 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.

Summary § Future 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.