Solid Waste Disposal (College Board AP® Environmental Science): Study Guide

What is solid waste?

Defining solid waste

• For this unit, solid waste is considered to be

  • any discarded material that is not a liquid or gas and is generated in domestic, industrial, business, and agricultural sectors

• However, the Resource Conservation and Recovery Act (RCRA), passed in 1976, defines solid waste as

• According to the U.S. Environmental Protection Agency (EPA), to be considered a solid waste, the material must be discarded by being

• What can be agreed on, though, is that waste disposal and management is a major concern globally

• The World Bank estimates that by 2050, global waste will have increased from 2.01 to 3.4 billion tonnes per year

• Most waste is generated in the United States at a rate of 811 kg of waste per person per annum, and around half of that ends up in landfill

• The only country not to send waste to landfill is Switzerland and whilst the Swiss produce 706 kg of waste per person, 210 kg is recycled, 333 kg incinerated and the remaining 163 kg is compostable waste

• Chile is the worst country and recycles only 2 kg per person; 417 kg of waste per person ends up in landfill 

• In LDCs, over 90% of waste is openly dumped or burned

Sources of solid waste

• There are several sources of solid waste, including:

  • Residential waste from households, such as food scraps, cans, glass, paper, plastics, etc.

  • Municipal waste is from municipal services, such as street sweeping, park maintenance, and other public services

  • Agricultural waste is generated by farming activities, such as crop surplus, livestock manure, and other agricultural by-products

  • Commercial includes business waste like packing materials, office paper, and other business-related items

  • Medical waste includes hospitals and other healthcare facilities, such as medical equipment, sharps, and other hazardous materials

  • Industrial waste is generated by factories and industrial processes, such as chemicals, machinery parts, and manufacturing by-products

  • Construction and demolition waste, such as wood, bricks, and other materials produced during the building and demolishing process

Classifying solid waste

• There are two main categories of solid waste

  • municipal

  • non-municipal

• Nearly 99% of US solid waste is non-municipal, from

  • agriculture, such as pesticide containers

  • industry, mining, oil and gas operations such as ash, scrubber sludge and construction waste

• However, municipal solid waste comes from homes, businesses, and cities

• It consists mostly of paper, cardboard, plastics, food scraps, yard garbage, metals, wood, and glass

• Municipal trash content varies by place and season

• Hazardous waste comes into the category of solid waste and is subject to strict regulations

  • This type of waste is

    • toxic

    • carcinogenic

    • mutagenic

    • teratogenic

    • extremely flammable

    • corrosive

    • explosive compounds

• Hazardous solid waste can harm humans and the environment; however, some home, small business, and mining waste are exempt from US hazardous waste restrictions

Legislation and waste management

• The Resource Conservation and Recovery Act (RCRA) is a U.S. federal law that gives the Environmental Protection Agency (EPA) control over both solid and hazardous waste

  • The EPA's main goals are to protect people and the environment from the dangers of improper waste disposal, keep resources from being wasted, and make sure that waste management systems are environmentally acceptable

  • Key focus areas:

    • Hazardous waste: RCRA establishes a 'cradle-to-grave' system for tracking and managing hazardous waste, from its generation to its final disposal

    • Solid waste: the law also regulates non-hazardous solid waste to reduce landfill use

    • Resource conservation: to conserve resources and energy, the Act encourages waste reduction and recycling

• Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as 'Superfund,' provides the federal government authority to respond to the release or potential release of hazardous substances into the environment

  • The law was passed in 1980 and gives the federal government the power to clean up places where waste has been improperly disposed of or managed

  • Sites include factories, processing plants, landfills, and mining sites

  • CERCLA provides the framework for the assessment and cleanup of contaminated sites

  • The CERCLA process takes years to finish because of the studies and public consultations needed to determine the type and amount of contamination, along with the risks and costs of cleaning up the site
    

Solid waste in landfill

• Different waste types demand different disposal methods

• Waste management includes

  • recycling

  • composting

  • incineration

  • ocean dumping

  • landfilling

• Landfill is the burial of waste in hollowed-out land, where it is left to decompose over time

• Waste can also be buried in disused/abandoned mines and quarries

• In the past, landfill sites were unmanaged and prevention of environmental damage minimal or non-existent

• Modern landfill sites are lined to prevent leachate from running out of the site

• Methane is produced as decomposition begins, which is either flared off or collected and used to generate electricity (gas to energy process)

• Closed landfill sites are landscaped and used as golf courses or housing, etc.

• However, many older landfill sites are still contaminated and releasing methane into the atmosphere

• Landfill sites are 'smelly' and attract vermin and rainwater can surface wash chemicals into rivers

Advantages

• Centralised waste management: provide a single location for managing large volumes of waste

• Flexible: handle a wide range of materials, including non-recyclable materials

• Lower operational costs: relatively inexpensive compared to other waste disposal methods

• Reduced environmental impact: can be engineered with liners and leachate collection systems to minimise environmental impact

• Gas capture potential: some capture methane gas, which can be used as an energy source

What is e-waste?

• Electronic waste (e-waste) is any discarded electronic devices and equipment, such as computers, televisions, smartphones and appliances, that can contain hazardous materials like lead, mercury and other components that require specialized handling and disposal

• With the rapid advancement of technology, electronic waste, or e-waste, has become a growing concern

• The volume and composition of e-waste can change over time due to the introduction of new devices, upgrades, and the speed at which older electronics become obsolete (i.e. they become out-of-date)

• Increasing awareness of e-waste management and the implementation of regulations can influence the handling and disposal practices of electronic waste

Sanitary municipal landfill

• The term 'sanitary' refers to the efforts to contain contamination and the spread of disease

• A 'sanitary municipal landfill' is a controlled and engineered waste disposal site

• Solid waste is compacted into layers and covered daily with soil

• Leachate is managed to protect groundwater

• Modern sanitary landfills are elaborate structures that separate waste from the environment until it becomes inert

• Landfills typically have

  • clay and durable synthetic plastic bottom liners

  • a leachate collection system to remove liquids

  • a stormwater management system to keep surface water out of the waste

  • methane collection system to remove landfill gas

  • divided into cells to increase the rate of decomposition and reduce odors

• Landfill cells are filled and closed successively and

  each cell can be up to 2,500 square feet or 20 acres

• Two feet of compacted clay, a strong plastic liner, and a nonporous geotextile membrane line a new cell hole

• A granular layer on the outliner lining funnels liquids into a leachate collection device

• That is covered by two feet of earth before waste is added

• Often, the first layer of garbage uses old mattresses to protect the lining

• Municipal solid trash is then deposited into the cell and compacted by tractors

• To reduce odors, bugs, rainwater runoff, waste burning, and scavenging, the garbage is covered daily with a minimum of 6 inches of soil

• Wells and trenches for landfill gas collection are erected periodically as the landfill fills

• When full, the cell is capped with plastic sheeting and covered with topsoil

• This will be seeded with plants over the decades-long post-closure monitoring phase