Topic 8.10 Notes – Waste Reduction Methods

What Waste Reduction Methods Are

Waste reduction means changing how materials are made, used, collected, and processed so less waste needs final disposal.

The usual hierarchy goes from best to least preferred:

1. Source reduction
2. Reuse
3. Recycling and composting
4. Energy recovery
5. Treatment/disposal

That order matters because these methods act at different points in the waste stream.

• Source reduction prevents waste from being created in the first place.
• Reuse keeps an item in service longer.
• Recycling and composting happen after waste has already been generated.
• Energy recovery and landfill restoration reduce harm after disposal, so they are mitigation, not prevention.

A common test trap is mixing up waste diversion with waste prevention.

• Diversion means keeping waste out of landfills or incinerators.
• Prevention is better because you avoid collection, transport, and processing too.

The diversion rate is

$$\text{Diversion rate}=\left(\frac{\text{mass reused, recycled, or composted}}{\text{total mass of waste generated}}\right)\times 100$$

Be careful with categories. If composting is already included in a recycling/diversion total, don’t add it again.

Main Waste Reduction and Mitigation Methods

Source reduction and reuse

Source reduction cuts waste before it exists.

• less packaging
• durable or repairable products
• reusable items instead of disposable ones
• buying only what is needed

This has the biggest benefit because it avoids impacts from resource extraction, manufacturing, transport, and disposal.

Reuse extends product life with little reprocessing.

• refillable containers
• repaired appliances
• donated computers
• salvaged building materials

Drawbacks do exist.

• items may need collection, cleaning, storage, or repair
• older products may be less efficient or less safe

Recycling

Recycling converts certain solid wastes into new products.

Common materials include:

• metals
• glass
• paper
• cardboard
• some plastics

The process usually goes in this order. Transport to a recycling facility often comes right after collection, as the diagram shows.

1. collection
2. sorting/separation
3. contaminant removal
4. cleaning/preparation
5. reprocessing into feedstock
6. manufacturing into new products

Recycling process flowchart

Benefits:

• lowers demand for virgin raw materials and minerals
• reduces some mining impacts
• conserves landfill space

Drawbacks and limits:

• energy-intensive and costly
• transportation and processing create emissions
• contamination can ruin loads
• some materials are downcycled into lower-quality products instead of recycled in a closed loop

Composting

Composting is the decomposition of organic matter such as food scraps, paper, and yard waste. The product is compost, which can be used as fertilizer or a soil amendment.

It needs:

• organic feedstock
• decomposers
• moisture
• oxygen
• a mix of carbon-rich and nitrogen-rich materials

Benefits:

• diverts biodegradable waste from landfills
• returns nutrients and organic matter to soil
• can reduce methane formation compared with landfill disposal

Drawbacks:

• odor
• rodents
• contamination
• management and labor needs

E-waste reduction

E-waste includes computers, cell phones, televisions, and monitors.

Best options together:

• reuse
• repair
• refurbish
• donate
• recover components
• recycle through proper facilities

Important materials:

This matters because lead and mercury can leach from landfills into groundwater if e-waste is improperly disposed of.

Energy Recovery and Landfill Mitigation

Waste-to-energy combustion

This means burning municipal solid waste to heat water, make steam, turn turbines, and generate electricity.

Benefits:

• greatly reduces waste volume
• produces energy

Drawbacks:

• expensive
• creates ash
• can release CO2, particulates, nitrogen oxides, and heavy metals

It can also compete with recycling and source reduction if the facility needs a steady supply of trash.

Landfill gas-to-energy

In landfills, organic waste decomposes anaerobically and forms methane and carbon dioxide. Wells and pipes collect the gas, and methane is combusted for heat or electricity. The diagram below shows that flow from buried waste to gas collection, cleanup, electricity generation, and the grid.

Landfill gas-to-energy system

Benefits:

• captures useful energy
• reduces uncontrolled methane release
• combustion of landfill gas can turn turbines and generate electricity
• this process reduces landfill volume

Drawbacks:

• not all methane is captured
• systems need monitoring
• combustion still produces CO2 and other pollutants

Restoring former landfills

Closed landfills can be capped, revegetated, and reused as parks, habitat, open space, or solar sites. Freshkills Park is the classic example.

Benefits:

• habitat
• recreation
• improved appearance
• less pressure to develop undeveloped land

Drawbacks:

• buried waste remains
• methane and leachate monitoring continue
• settling and land-use limits remain

Matching Each Method to Its Benefit and Drawback

This section is often tested as “propose one method and explain one benefit and one drawback.”

• Recycling reduces virgin mineral demand, but it is energy-intensive and costly.
• Composting creates useful soil amendment, but it may cause odor and attract rodents.
• E-waste reuse/recycling keeps lead and mercury out of landfills and groundwater, but it needs specialized safe processing.
• Waste combustion reduces waste volume and produces electricity, but it causes air pollution and ash.
• Landfill gas recovery reduces methane emissions and generates electricity, but it only manages waste after burial.
• Landfill restoration recovers land for use, but it does not remove existing waste or long-term monitoring needs.