Solid Waste

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Objectives
Discuss what is solid waste, source reduction, secondary waste prevention (for example, recycling), and final disposal


Introduction

Definition

Mixed municipal waste.JPG
Solid Waste 
Any unwanted product which is not a liquid or gas in our surroundings and from our daily products.

Types

Type of solid waste:

  • mining waste (including oil and gas production) - the largest amount by volume
  • agriculture waste (including food processing)
  • industrial solid waste (nonhazardous)
  • sewage sludge
  • construction and demolition waste - sometimes included in other groups
  • hazardous waste
  • municipal solid waste (MSW) - waste from the community including household and commercial wastes

The rest of this page concerns only municipal solid waste.

Composition

Solid waste composition varies greatly between countries. For a comparison of waste composition between OECD countries and Asian cities see this page.

3R's

This is the universal recycling symbol. But the three "arms" actually stand for reduce, reuse, and recycle. They should always be considered in that order.


Source Reduction

Definition

Source reduction 
Reducing the amount of waste generated

Source reduction means no waste is produced and, therefore, none to manage.

Methods

There are no list of specific methods for source reduction. Methods will need to be applied on a case-by-case basis.

Methods include:

  • Decreasing consumption
  • Changing processes to produce less waste
  • Redesigning products to make them easy to repair, resuse, or recycle
  • Designing products to last longer
  • Reduce packaging
  • Much of packaging is done simply to sell a product (advertising, marketing, money!)
  • To see examples of overpackaging go here and here.

Secondary Waste Prevention

Reuse

Reuse 
Use a product again without destroying it

Example

  • Refillable glass bottles
  • They are just washed and refilled

Recycling

Recycling 
Converting wastes into new products

Examples (These three examples show the different reasons for recycling)

  • Aluminum
  • Production of raw aluminum is by electrolysis, which consumes a large amount of electricty (aluminum production consumes about 15kWh per kilogram. Aluminum production represents 5% of US electicity)
  • Recycling aluminum only requires melting of aluminum, and therefore, uses only 5% of the energy used to make it from ore.
  • Paper
  • Paper accounts for a large percentage of solid waste (more than 30% in some countries)
  • Therefore, recycling reduces landfill space considerably.
  • Electronic waste (e-waste)
  • Electronic waste contains many valuable materials: gold, silver, aluminium, platinum, palladium, copper, tin, tantalum, nickel, lithium
  • However, recover of some materials requires use of very strong acids
  • Electronic waste also contains many toxic chemicals: mercury, lead, cadmium, chromium, beryllium

Composting

Composting 
Using soil microorganism to decompose organic matter
  • Especially useful for food wastes, especially at the household level
A compost pile. Note the steam coming from the pile -- bacteria produce heat. This heat will kill pathogens.
Compost, the result from composting


Waste Management

Incineration

A municipal waste incinerator in England
Incineration 
Controlled burning of solid waste

Pros

  • reduces volume
  • produces energy

Cons

  • produces air pollution
  • toxic ash


Landfills

A landfill in Hawaii, USA. Note the black liner on the left.
Landfill 
burying waste underground in a specially built site

Landfill includes:

  • A clay base
  • A plastic liner
  • Daily soil cover
  • Top clay layer (applied when landfill is full)

Two things landfills create:

  • Methane gas
  • Can create dangerous pockets
  • Can be recovered for use as fuel
  • A liquid called leachate
  • can get into groundwater
  • collected by a leachate collection system