What happens to our solid waste, and how can we move from disposal to a circular economy?
The sources and types of solid waste, methods of waste disposal including landfill and incineration and their impacts, and the waste hierarchy of reduce, reuse and recycle moving towards a circular economy.
A focused answer to AQA A-Level Environmental Science 3.4.4, covering sources and types of solid waste, disposal methods including landfill and incineration, their impacts, and the waste hierarchy and circular economy.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
AQA wants you to describe the sources and types of solid waste, explain methods of disposal (landfill and incineration) and their impacts, and explain the waste hierarchy of reduce, reuse and recycle as a route towards a circular economy. Command words are Describe, Explain and Compare, so be ready to weigh landfill against incineration.
Sources and types of solid waste
The rising volume of waste in industrialised economies reflects a linear take, make, dispose model, which is the problem the circular economy is designed to replace.
Landfill
In landfill, waste is buried in engineered, lined sites. Problems include:
- Methane, a potent greenhouse gas, produced as organic waste decomposes anaerobically (without oxygen) in the buried mass.
- Leachate, the polluted liquid formed as rain percolates through the waste, which can contaminate groundwater if the liner fails.
- Land use and loss of habitat, plus odour, pests and litter.
Modern sites are lined to contain leachate and capped to collect the methane, which can be burned to generate electricity, turning a pollutant into a partial energy source.
Incineration
Incineration burns waste at high temperature, which reduces its volume by around ninety percent and can recover energy (energy-from-waste plants generate electricity and heat). However, it releases carbon dioxide and other gases, can emit toxic substances such as dioxins if combustion and gas cleaning are poor, and leaves ash (some of it hazardous) that must still be disposed of.
The waste hierarchy and circular economy
Reducing and reusing rank above recycling because they avoid the energy and pollution of reprocessing entirely; recycling, while valuable, still consumes energy to collect, sort and remanufacture materials.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20196 marksCompare landfill and incineration as methods of disposing of municipal solid waste, considering their environmental impacts.Show worked answer →
A compare needs paired points naming both methods. Markers reward at least three contrasts plus a comment.
Volume and land: incineration reduces waste volume by about 90 percent so needs little land, whereas landfill buries waste largely intact and consumes large areas of land.
Greenhouse gases: landfill produces methane (a potent greenhouse gas) from anaerobic decomposition, whereas incineration produces carbon dioxide directly but can recover energy that displaces fossil-fuel use.
Other pollution: landfill risks leachate contaminating groundwater, whereas incineration can release toxic gases and dioxins if poorly controlled, and leaves ash to dispose of.
A strong answer notes both are low in the waste hierarchy and that reducing and recycling are preferable.
AQA 20224 marksExplain how recycling a metal such as aluminium conserves resources and reduces environmental impact compared with making it from ore.Show worked answer →
Markers award marks for energy, raw-material and pollution arguments, each linked.
Energy: recycling aluminium uses only about 5 percent of the energy needed to extract it from bauxite by electrolysis, so it greatly reduces fossil-fuel use and associated carbon dioxide.
Raw materials: recycling conserves finite bauxite ore and avoids the habitat destruction, spoil and red-mud waste of mining and refining.
Pollution: less mining, refining and smelting means less air and water pollution. A full-mark answer makes the energy point explicit with the rough percentage and links it to conserving the ore and cutting emissions.
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