Waste Management and Circular Economy
Exam focus
Waste streams, segregation, treatment options, rules and the shift from linear to circular models.
Core rules
- Waste hierarchy: prevent > reuse > recycle > recover (composting, energy) > dispose (landfill).
- Segregation at source: wet biodegradable, dry recyclable, hazardous, e-waste and biomedical waste.
- Biomedical waste colour codes are yellow (human anatomical, soiled, chemical), red (contaminated recyclable plastics), white (sharps) and blue (glass, metallic implants).
- Composting and vermicomposting are aerobic; biogas from anaerobic digestion produces methane-rich gas and digestate.
- A sanitary landfill needs a liner, leachate collection and gas venting. Open dumping causes leachate, vectors and methane release.
- Circular economy: design out waste, keep materials in use, regenerate natural systems. Extended Producer Responsibility makes producers responsible for end-of-life plastic and e-waste.
Worked example
A city generates 500 t/day of waste; 60% is wet, 25% dry recyclable and 15% inert. Wet waste = 300 t/day. If composting recovers 60% of wet waste as compost, compost = 180 t/day. Apply percentages to the correct fraction, not the total, and use recovery rates to estimate the landfill load.
Traps
- Treating incineration as recycling; it destroys materials and can emit dioxins if poorly run.
- Mixing biomedical sharps into general dry waste.
- Ignoring leachate in landfill design.
- Defining circular economy as just more recycling rather than redesign and reuse.