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 waste, but not household food waste)
  • industrial solid waste (nonhazardous)
  • sewage sludge
  • construction and demolition waste - sometimes included in other groups
  • hazardous waste (wastes which are flammable, corrosive, reactive, or toxic)
  • 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 between countries. For information on different solid waste compositions see report (pdf)

Environmental Problems

Plastics

Source of Plastics - almost all plastics are made from oil. This is a concern becuse of the role oil has in contributing to global warming.

The biggest problems are due to Single-use plastics.

Many people believe the myth that the solution to the plastic problem is simply recycling. Yet many of the commonly used plastic products cannot be recycled including: styrofoam, plastic wrap, most plastic bags, some plastic cutlery, and plastic straws.

A solution which many people have claimed as a solution is biodegradable plastics. However, recent studies have shown that degradation of these plastics creates microplastics. These in turn have been shown to be toxic.

A major concerned for plastics is the Great Pacific garbage patch. This is a concentration of trash, mostly plastics, found in the North Pacific Ocean. There are actually two "patches" - one between Hawaii and California, and one between Japan and Hawaii. It is created due to the North Pacific Gyre.

This map shows the oceanic gyres
The Great Pacific garbage patch


Similar, but smaller, garbage patches have been found in all the other gyres.

One of the biggest problem is ingestion of plastics by animals, especially marine mammals and birds.

A plastic bag which looks like a jellyfish. Marine mammals and sea turtles often mistakenly eat these plastic bags.
A sea turtle caught in a ghost net. Plastics from fishing account for 46% of the Great Pacific garbage patch


Electronic waste (E-waste)

Electronic waste contains many valuable materials: gold, silver, aluminium, platinum, palladium, copper, tin, tantalum, nickel, lithium.

However, to recover some of these requires use of very strong acids. This can lead to problems with health and safety.

Electronic waste also contains many toxic chemicals: mercury, lead, cadmium, chromium, berylium.

Integrated Waste Management

Integrated waste management 
A variety of coordinated strategies for waste management and waste reduction

That is, all solid waste cannot be handled equally. Using a combination of methods and choosing the correct method for each type of waste are key.

Diagram showing integrated waste management and how the parts are related to each other

Ways that are not part of good integrated waste management:

  • Open dumping
  • Improper landfills
  • Uncontrolled burning ("open burning")
  • Exporting of wastes (especially [[w:Electronic waste#Global trade issues|E-waste]

The order of that we consider the methods in integrated waste management is important:

  1. Waste reduction
  2. Reuse
  3. Recycling/composting
  4. Final disposal

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.
  • Taxes (especially recently on single-use plastics)
  • Bans (especially on nonrecyclable products)

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)
  • E-wastes contains many toxic materials (see next section). Therefore, recycling reduces potential for toxic material to be leached out of landfills or released from burning.

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


Final Disposal

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
  • Is a greenhouse 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