Recycling of solid wastes — A/L Biology

What must I remember about Recycling of solid wastes?

• Solid waste management constitutes a major global environmental and public health imperative, governed by the Waste Hierarchy framework: Refuse, Reduce, Reuse, Repurpose, Recycle, and Recover energy before final disposal.
• Composting of biodegradable municipal solid waste: Aerobic biological decomposition of solid organic wastes (food scraps, yard waste, livestock manure) by succession of microorganisms (mesophilic bacteria -> thermophilic bacteria e.g., Bacillus, Thermus -> actinobacteria and fungi), producing nutrient-rich organic compost humus.
• Sanitary Landfills vs Open Dumps: Open dumps create open vectors, odors, and uncontrolled toxic leachate; Engineered Sanitary Landfills feature impermeable clay and geomembrane liners, leachate collection and treatment systems, and methane gas capture wells.
• Recycling of inorganic wastes: Mechanical and chemical reprocessing of non-biodegradable post-consumer materials (glass, aluminum cans, ferrous metals, plastics: PET, HDPE) reduces raw material extraction, saves energy, and curtails landfill footprint.
• Public health and ecological hazards of mismanaged solid waste: Proliferation of disease vectors (rats transmitting leptospirosis, mosquitoes transmitting dengue/chikungunya), plastic ingestion and microplastic entanglement in terrestrial/marine food webs, and open burning releasing toxic dioxins and furans.

Test yourself (1 minute)

1. Thermophilic stage of composting

   Internal core temperatures rise to 55-65°C due to intense microbial exothermic metabolic activity, effectively pasteurizing the compost by killing human enteric pathogens, weed seeds, and insect larvae.

2. Carbon-to-Nitrogen (C:N) optimum ratio

   Optimum aerobic composting requires a balanced C:N ratio around 25:1 to 30:1; excess carbon slows decomposition, while excess nitrogen leads to foul-smelling ammonia (NH3) gas emissions.

3. Leachate generation & groundwater hazard

   Rainwater percolating through unlined open garbage dumps dissolves toxic organic and heavy metal pollutants into dark toxic liquid called 'Leachate', severely contaminating subterranean aquifers.

Practise Recycling of solid wastes questions today

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 9

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What comes next?

Next in the syllabus

Where does Recycling of solid wastes fit in the syllabus?

Year 2 · Term 3