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Composting of Solid Waste, Objectives & Its Steps

By: Haseeb Jamal / On: Jul 06, 2017 / Solid Waste
Composting of Solid Waste
 
 

Composting of Solid Waste:

  • Composting of Solid Waste is defined as "biological decomposition of biodegradable organic constituents of waste under controlled conditions to a state sufficiently stable for nuisance free storage & handling and for safe use in land applications".
  • About 70% of municipal solid waste is decomposable or compostable.
  • Main organisms involved in composting are:
    • actino-mycetes (filamentous bacteria), fungi and protozoa.

Objectives of Composting of solid waste

  • To transform biodegradable Organic matter into biologically stable material thereby reducing the original volume of the waste,
  • To destroy pathogens, insect eggs and other unwanted organisms and weed seeds that may be present in municipal solid waste.
  • To retain maximum nutrient content; and
  • To produce a product that can be used to support plant growth and as a soil amendment as fertilizer and soil conditioner.

Composting time depends on:

  1. The nature of waste.
  2. Moisture content of solid waste.
  3. Available nutrients in the solid wastes.
  4. Other environmental factors.
  5. Under controlled conditions, can be made more effective and efficient.
  6. Organic matter + O2 + nutrients + microbes ------- New cells + resistant OM + CO2 + H2O + NH3 + SO4 + heat.
  7. Reduces weight/volume of the organic fraction of MSW.
  8. Produces compost ( a humus like material that can be used as a soil conditioner).
  9. To produce methane - Bio Gas.

Also See: Hospital Waste | Types of Hospital Waste

Steps in Composting of solid waste:

PRE PROCESSING

Receiving

  • Sorting/separation: removal of recyclable material, metals, debris, glass etc. -affects the quality of

Size Reduction/Screening:

  • to provide greater surface area for microbes to attack, to improve insulation, to facilitate homogenizing of initially heterogeneous material, to reduce depth for oxygen diffusion.
  • If size is too small, it impedes the diffusion of oxygen and CO2 from the sites being attacked especially during thermophylic stage when Oxygen demand is the highest.
  • Typical range for feed material = ½ - 2 inches.
  • Adjustment for waste properties (e.g C/N ratio)
  • Decomposition and curing/maturation

Types are: Static piles and in-Vessel composting

  • Preparation and marketing of the final compost product: Grinding, screening, air classification, blending with various additives, granulation, bagging, storage and transportation

Windrow Composting

  • Triangular piles 7 feet high and 14-16 feet wide at the base
  • Turning by front end loader or mechanical turner twice per week
  • Composting period 2-6 weeks
 

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