Composting
Definition
Biological transformation of biodegradable waste into water, CO2, energy and a composed matter
Reduce the volume of waste destined for landfill or incineration
For soil amendment, improve soil nutrients, reduces erosion and help suppress plant diseases.
These organic material undergoes microbial decomposition and produces a humus material known as compost
Organic fraction MSW can be composed of protein, amino acids, lipids, celullose, carbohydrate, lignin and ash
Objective
To transform the biodegradability organic materials into a biologically stable material and int he process to reduce the original volume of waste.
To destroy pathogens, insect,eggs, and other unwanted organisms and weed seeds that may present in MSW
To retain the maximum nutrient(nitrogen, phosphorus, and potassium) content.
To produce a product that can be used to support plant growth and as a soil amendment
Properties
A brown to very dark brown colour
A low carbon-nitrogen ratio
A continually changing nature due to the activities of microorganisms
A high capacity for cation exchange and water absorption
Step
Pre processing of MSW
Receiving MSW
Removal of recoverable material
Size reduction
Adjust the waste properties such as carbon-nitrogen ratio, addition of moisture and nutrients
Decomposition of organic fraction of MSW
Windrow
Static pile
In-vessel composting
Preparation and marketing of final product
Fine grinding
Screening
Air classification
Blending with various additive
Granulation
Baging
Storage
Shipping
Facility Design
Process Variables
Particle size
Seeding and mixing requirements
Total oxygen reuirements
Control of pathogens
Moisure content
Respiratory Quotient (RQ)
Techniques
Factors to design composting facilities
Type of waste
System selected
Environmental issues
Cost of implementation
Agitated method
Static method
Applications
Yard waste such as leaves, small tress branches
Organic fraction of MSW such as food wastes, thin plastic, papers
Partially processed commingled MSW which is waste that are not separated before arriving at the processing site
Co-composting of organic fraction of MSW with wastewater sludge
Example of composting
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