Introduction
This lesson explores the complex and persistent issue of plastic waste in landfills, focusing on how plastics behave once buried and the environmental risks they pose over time.
Learners will gain insights into the slow degradation of plastics under landfill conditions—primarily due to low oxygen, lack of sunlight, and stable temperatures—which leads to the generation of microplastics and chemical leachates. The lesson explains the formation and composition of landfill leachate, a contaminated liquid that percolates through waste layers and often carries harmful substances such as bisphenol A (BPA), phthalates, and microplastics into soil and groundwater. It also describes how surface runoff from landfill sites acts as another major pathway for plastic pollution, especially in poorly managed landfills.
Through real-world research findings and field case studies, the lesson highlights the environmental and health implications of landfill plastic pollution—from soil degradation and ecosystem disruption to risks for human health. Learners are also introduced to engineering, regulatory, and technological mitigation strategies, such as improved landfill design, leachate treatment, plastic bans, and international best practices.
The content reinforces the importance of monitoring and managing plastic waste within a circular economy framework to prevent long-term leakage into the environment.
Lesson Learning Outcomes
After completion of this lesson, learners will be able to:
Understand how plastic waste behaves in landfill environments and why degradation is extremely slow under anaerobic conditions.
- Plastics in landfills are shielded from oxygen, light, and microbial activity, making them persist for hundreds of years without breaking down significantly.
Identify the formation process and environmental impact of landfill leachate containing microplastics and chemical additives.
- Learners will explore how rainwater filtering through waste layers becomes chemically contaminated, forming leachate that can affect soils and water bodies.
Explain the role of rainfall, surface runoff, and leachate pathways in transporting plastics from landfills into surrounding ecosystems.
- This includes understanding how stormwater can mobilize and spread plastic particles from landfill surfaces into rivers, fields, and oceans.
Recognize the health risks associated with exposure to leachate contaminants such as BPA and phthalates.
- These toxic substances can interfere with hormones and are linked to diseases including cancers and reproductive disorders.
Analyze how landfill design (e.g., liners, caps, drainage) can mitigate or exacerbate plastic pollution and leakage.
- Proper engineering—such as using HDPE liners and leachate collection systems—can significantly reduce environmental contamination.
Evaluate the effectiveness of leachate treatment technologies and waste management strategies in reducing pollution.
- Technologies like reverse osmosis and biofilters can remove microplastics and toxicants before leachate reaches natural water systems.
Distinguish between engineered and uncontrolled landfills in terms of plastic leakage risk.
- Uncontrolled dumps lack protective barriers, posing higher risks of pollution, especially in low-income or disaster-affected areas.
Investigate current scientific data and case studies regarding microplastic migration in soils and groundwater.
- Students will review evidence showing how plastic particles travel through porous soils and persist in aquifers, affecting agriculture and drinking water.
Propose solutions to reduce plastic leakage from landfills, including policy, design, and behavior change approaches.
- These may include stricter landfill regulations, improved material sorting, public education, and bans on non-recyclable plastics.
Reflect on the long-term environmental legacy of plastic waste in landfills and their role in supporting circular waste systems.
- Learners will consider how landfill plastic impacts future generations and why upstream reduction is more sustainable than downstream control.
