Issues of Solid Waste Disposal Methods (College Board AP® Environmental Science): Revision Note

Landfill is the general term for a site where solid waste is buried in the ground

• Modern engineered landfills (sanitary landfills, covered in the next spec point) reduce many of the issues below, but the underlying problems still apply where the engineering is absent or fails

Landfills can cause many environmental problems, including air and water pollution, land degradation, and climate change

Landfilling is becoming less acceptable and feasible due to limited landfill capacity, tighter environmental restrictions, and public opposition

Landfills produce methane, a potent greenhouse gas

A significant amount of land is needed for landfill, which can be difficult to find

There is a risk of groundwater and soil contamination from leachate

Uncontrolled fires in landfills release harmful dioxins 

Landfills need long-term monitoring and management long after closure and usually have incomplete decomposition and settling

• The process of waste decomposition in landfills is slow, often taking years for organic materials to break down fully due to anaerobic conditions

Landfills often cause noise and smell pollution in less affluent urban outskirts

• This disproportionately impacts the health and quality of life for the residents in these areas

• It also reduces property value due to the landfill and supply trucks

Waste is burnt, which reduces the volume of waste to landfill, but the remaining ash needs to be disposed of

Electricity can be generated from waste by two main pathways (collectively called energy recovery):

• (1) Direct incineration of waste: waste is burned in a furnace → heat boils water → steam drives a turbine → turbine generates electricity

• (2) Landfill gas capture: organic waste decomposing anaerobically in landfills produces methane, which is collected via wells and pipes, then burned → heat boils water → steam drives a turbine → turbine generates electricity

Both pathways reduce the use of fossil fuels but can lead to the release of toxic chemicals into the air or water

It releases CO, CO₂, dioxins, halogens, particulates, SOₓ, and NOₓ

The waste ash is collected and taken to a specialised landfill

• But the ash can be contaminated with toxins that can leach out into the environment

Particulates are captured by high-efficiency filtering

Energy recovery incineration is better than simple incineration because:

• It disposes of gas, liquid and solid waste

• It is a practical method of disposing of certain hazardous waste materials (such as biological medical waste).

• Waste ash can be repurposed in roads and concrete (depending on type of ash)

• Waste ash can also be reprocessed to extract recyclable metals and glass

• High-efficiency filters remove many of the emissions

• It reduces the amount of landfill waste 

Incineration accounts for 15% of US municipal solid trash, although environmental concerns and high running costs have made it less popular

A sanitary landfill is an engineered landfill designed to reduce environmental harm. Key features include:

• Impermeable liner (clay + plastic) at the base — prevents leachate from contaminating groundwater

• Leachate collection system — removes and treats contaminated water

• Daily soil cover over the waste — limits odour, pests, and fires

• Landfill gas (methane) collection — captured for flaring or electricity generation

• Final cap at closure — seals in the waste and prevents water infiltration

Despite these controls, sanitary landfills still have several issues:

Sanitary landfills do not accept some items, and their illegal disposal can lead to environmental problems

Used rubber tires can become breeding grounds for mosquitoes that can spread disease when they are not disposed of properly

• Tires can catch fire and release pollutants that cause respiratory issues

As with landfills, sanitary landfills also have issues with odor, vermin, habitat destruction and methane production

Other issues include

• improperly sited landfills near watercourses or groundwater supplies

• inadequate wetness that slows decomposition

• too much water leaking through or around the landfill's waterproof lining

'Ocean dumping,' or dumping solid waste at sea, can harm marine ecosystems and biodiversity through

• Entangling in fishing nets, plastic rings, and other trash can injure or kill animals

• Ingestion of waste by marine life

  • Multiple marine species confuse plastic for food, causing intestinal obstructions and malnutrition

• Plastics degrade slowly into microplastics and enter the food chain by accumulating in the bodies of marine organisms

• Accumulated waste can smother coral reefs, seagrass beds, and other important marine habitats, impacting the organisms that rely on them

• Potential toxin release from degrading barrels of waste oil and radioactive material into the ocean

• Coastal communities are impacted from washed-up debris