Lecture Week 4

Solid Waste Management Overview

Introduction to Solid Wastes

Definition: Solid waste refers to all unwanted or discarded material, including:

  • Agricultural: Crop residues and animal manure (largest contribution, ~50% in the USA)

  • Mining: Waste from mineral extraction (second largest, ~33% in America)

  • Industrial: Wastes from industries apart from mining, includes hazardous materials.

  • Municipal Solid Waste (MSW): Commonly known trash; includes packaging, food scraps, etc.

Global Production: Currently 2.01 billion tons/year, projected to hit 3.4 billion tons in 30 years.Per Capita Production:

  • World avg: 0.74 kg/person/day

  • USA: 2 kg/person/day

  • China: 1.2 kg/person/day (HK: 1.53 kg in 2021)Synonyms: Garbage, rubbish, refuse.

Types of Solid Waste

Composition in Hong Kong (2021):

  • Plastics: 21%

  • Food: 30%

  • Metals: 2%

  • Glass: 2%

  • Paper: 20%

  • Others: 25% (bulky and miscellaneous)

Current Waste Management Practices

Key Management Techniques

  • Waste Reduction, Reuse, Recycle (3R): Essential approaches to lower waste generation.

  • Landfill Types:

    • Sanitary Landfill: Isolates waste; leachate can be processed.

    • Secured Landfill: Specifically for hazardous wastes; stricter regulations.

Treatment Methods

  • Open Dumping: Illegal in developed countries; leads to severe health risks and environmental pollution.

  • Sanitary Landfill: Waste is compressed and covered; biogas collected; leachate treated; cheaper, but pollutes if managed poorly.

  • Incineration: Converts waste to ashes and gas; effective in space-limited regions like Japan, but can be costly and produce toxic emissions if not managed properly.

  • Composting and Anaerobic Digestion: Biological methods to convert organic waste into soil amendments or biogas.

Waste-to-Energy (WTE) Plants

  • Amager Bakke, Copenhagen: Significant WTE facility; reduces waste volume while generating energy.

    • Burns 400,000 tons of waste annually and contributes to district heating.

Special Waste Considerations

  • E-Waste:

    • Includes discarded electronic equipment; poses significant environmental hazards if mismanaged.

    • Extended Producer Responsibility (EPR): Producers are responsible for disposal of their products post-consumer use.

  • Leachate Management and Treatment

    • Leachate Overview

      • Definition: Liquid that leaches through a landfill, consisting of contaminants.

      • Key Parameters:

        • Total Organic Carbon (TOC)

        • Chemical Oxygen Demand (COD)

        • Biochemical Oxygen Demand (BOD)

        • Nitrogen parameters (like NH4-N)

    • Treatment Technologies

      • Ammonia Stripping: Utilizes chemical processes to reduce ammonia concentration in leachate.

      • Biological Treatment: Decomposes organic matter to meet regulatory discharge limits.

      • Advanced Techniques: Reverse osmosis, evaporation, and chemical coagulation for hard COD removal.

Waste Management Hierarchy

  • Prioritizes strategies from reduction to recycling and recovery, emphasizing a circular economy approach.

  • Encourages design principles that accommodate waste minimization and product life extension.

Conclusion

An integrated approach is essential for effective solid waste management.Continuous development of innovative methods plays a vital role in sustainable waste handling and environmental protection.