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Composting (Decomposition of the organic fraction of the MSW (Windrow…
Composting
Decomposition of the organic fraction of the MSW
Windrow
Oldest method
Constructed by forming the organic material to be composted into windrows
8 to 10 ft high
20 to 25 feet wide at the base
processed by shredding and screening
50 to 60 % moisture content
Temperature mainted at 50C
High rate system, twice per week
offensive odor release once turning the window
3-4 week for accomplished.
The compost is allowed to cure for another 3 to 4 weeks without turning
Residual decomposable organic materials are reduced by fungi
Static Pile Composting
known as Beltsville or ARS process
aerobic composting
composted for 3 to 4 weeks
Compost a wide variety of organic waste
cured for 4 weeks and longer
improve quality
cured compost are shred and screen
improve process and odor control
significant portion of the system in newer facilities are covered or enclosed
In vessel Composting
enclosed container
Mechanical system
minimize odors and process time
Advantageous
Process and odor control
Lower labor cost
Faster throughput
Smaller area requirements
Plug flow
Relationship between particles in the composting mass stays the same
First –in first-out principle
Dynamic system
Composting material is mixed mechanically
Facility design
Process variables
Particle size
Particle size distribution
Seeding and mixing requirements
Required mixing/turning schedule
Control of pathogen
Respiratory quotient (RQ)
Temperature and pH control
Factors to consider in designing of composting facilities
Types of waste
System selected
Environmental issues
Cost of implementation
Techniques
Agitated method
Material to be composted is agitated periodically
introduce oxygen
to control the temperature
to mix the material the material to obtain a more uniform product
Static method
Compost piles are laid on perforated pipes
The air is blown through the composting material
Covered by a layer of screened compost for insulation and odor control