COMPOSTING

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COMPOSTING

• Instructor
  
• Dr Mehdi Mokhtari

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• ?????? -????? ??????? ???????? ??????????????
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• ???????-????? ???????? PH ??? - ?????? ?????
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• Aerobic degradation of biodegradable organic
  waste eg. garden and food waste
• Organic matter O2?CO2 H2O ammonia SO4
  humus minerals
• Fast process- typically 4-6 weeks

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• Degraded product is a stabilised product which is
  added to soil to improve its structure, to act as
  a fertilizer and to retain moisture

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Finished compost

• humus-like, resembling rich topsoil
• resistant to further microbial decomposition

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Composting
Controlled aerobic partial degradation of organic
wastes
Microorganisms Compost or humus
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Factors affecting composting

• Aeration (O2)
• Nutrients
• CN ratio
• Moisture
• Temperature
• pH
• Time

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CN ratio

• Optimum 20 to 301
• Final product 15 to 201
• Microbes diet right at 25 to 301
• gt 301- N limiting, immobilize inorganic N
• gt101 (woody material-) C not available-bioavailab
  ility- composting takes longer

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• C/N ratio
• lt 201 nitrogen lost as ammonia (odors)
• Sources of N P - Organic wastes, manures,
  sludges, etc.
• Sources of C wood wastes, woodchips, sawdust

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• Example C/N Ratios
• Manure - 151 to 201
• Yard wastes - 201 to 801
• Municipal wastes - 401 to 1001
• Wood chips - 4001 to 7001

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Composting
GREENS
-- are rich in nitrogen
BROWNS
-- are rich in carbon
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Temperature

• Optimum 55-60o C (130- 140 oF)
• gt 140 F , kill mesophiles
• Human pathogens- 131o F human pathogens
• Plant pathogens- about the same
• Weed seeds 145 o F kills most
• Well run operations lt 140 oF

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Moisture

• Optimum water content 50 to 60
• lt 50 - composting slows due to microbial
  desiccation
• gt60 - compaction, development of anaerobic
  conditions, putrefaction/fermentation (odors)

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pH

• Optimum range 6.5 8.0
• Bacterial activity dominates
• Below pH 6.5
• Fungi dominate over bacteria
• Composting can be inhibited
• Above pH 8.0
• Ammonia gas can be generated
• Microbial populations decline

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• Level of acidity / alkalinity affects
• Nutrient availability
• Solubility of (potentially toxic) heavy metals
• Overall metabolic activity of microbes

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COMPOSTING TECHNIQUES

• Small-scale home composting
• simple compost heaps
• box or barrel composters
• commercial composter units
• digester units
• Commercial composting
• windrows
• aerated static piles
• in-vessel composting systems

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Reactor In vessel

• Agitated ????? ??????
• Static ????

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windrow
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  3- 2/5 ???? ??? 7/5 6/5 ??? ?? ??? ??? ???? ????
  ?? ?????. ? ??????? ???? ?? 2-1 ????? ??? ??? ?
  ?? ???? ????? ?? ??? ?????? ????? ?? ???.
• ?? ?? 5-4 ???? ?????? ?? ???. ?? ?? ??? ??? ????
  ??? 4-3 ???? ???? ?????? ????? ???

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Details of Windrow
Overhead sprinkler system
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High- rate windrow

• ?????? ????? 2-8/1 ???
• ??? ???? ?? 5-4 ???
• ?????? ???? ????? ???? ?? 2 ??? ???? ?? ????

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• Key organisms
• bacteria
• fungi
• Actinomycetes
• - play active role in decomposing organic
  matter

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Secondary organisms

• earthworms
• insects
• other soil invertebrates
• play a less significant role in decomposition
  process compared to microorganisms
• more important in mechanical breakdown of wastes
  (chewing, burrowing, movement, aeration)

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• Mesophillic phase lt 40o C
• initial decomposition of soluble substrates,
  several days, rapid CO2 loss, decrease in CN
  ratio immobilization of soluble N, S, P
• Thermophillic phase 40-65 oC ( 105-150o F)
• rapid breakdown proteins, cellulose, lignin,
  fats, waxes
• high O2 consumption, CO2 loss, decrease in CN
  ratio
• thermophillic bacteria (Thermus), Bacillus,
  actinomycetes, fungi

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• ????? (????) ?????? compost maturation
• ????? ?????? Compost stabilization

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Aerated Static Pile Composting

• Mixed materials built on bed with aeration pipes
  embedded
• Aeration by mechanical blowers
• Often used in biosolids (sludge) composting

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• ????? ?????? 4-3 ????
• ????? ?????? 4 ???? ? ?????

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Static Pile System
Pile height 3 to 6 m (10 to 20 ft)
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?????? ???????(in Vessel composting)

• ???? ???? ???? ????? ?????? 2-1 ???? ? ???? ????
  ???? ????? 12-4 ???? ?? ????

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In-vessel System

• Better control of temperature and oxygen
• Emissions of VOCs and OH gases can be captured
  and treated if necessary
• Better treatment efficiency due to improved
  mixing and mass transfer
• Less affected by environmental and weather
  conditions
• Capital intensive

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In-Vessel Composting

• More mechanically complex
• More expensive
• Smaller footprint (area)
• Relatively high operations maintenance costs

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In-Vessel Composting
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• 1 ?????? COD
• 2- ???? ??? ????? (Respiratory quotient RQ)
• 3- ?? ?????? ???? ??? ????? ??? ?? ???? ? ????
  ?????? ??? ??? ?? ???.
• 4 ????? ????? ????? ???
• 5 ?????? ?? ??????? ????????? ? ?????
• 6 ??? ???? ???????? ????????
• 7 ??? ???? ??????

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?????? ?????? ?? ?????? (co-composting)

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?????? ? ?????? (Blending Seeding )

• ??? ??????? ???? ????C/N ?????? ???? ????? ????
  ?????. ?????? ??? ??? ????? ?? ???? ????? ?? ????
  ??????????? ????? ?? ?????? ????? ???? . ?????
  ??? ???? 5-1 ???? ???

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• ???? ????? ?? ????? Curing ? ????? Stabilization
  ?????? ?? ?????? ????? ?? 18?2 ??? ?????? ???

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Vermi composting
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• Redworms in vermicompost act in a similar
  fashion, breaking down food wastes and other
  organic residues into nutrient-rich compost.
• Nutrients in vermicompost are often much higher
  than traditional
• garden compost

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• ?????????? ?????
• brandling worms (Eisenia foetida) ???
  ??????? ??????
• red worms or red wigglers (Lumbricus rubellus).
  ??? ????????? ??????

??? ????? ?? ?????? ???? ????? ?? ????? ?????
????? ??????????? ?????????? ????????
Allolobophora caliginosa
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• Food scraps can be continually added to the bin
  for up to 2 to 3 months, or until you notice the
  bedding material (shredded newspapers
• (non-glossy), computer paper, or cardboard)
• disappear. When the bedding disappears, harvest
• the worms and finished compost, then refill the
  bins with new bedding material.

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(E.Foetida)
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• Under optimum conditions, red worms can eat their
  own weight in food scraps and bedding in one day.
• On the average, however, it takes approximately 2
  pounds of earthworms (approximately 2,000
  breeders) to recycle a pound of food waste in 24
  hours. The same quantity of worms requires about
  4 cubic feet of bin to process the food waste and
  bedding (1 cubic foot of worm bin/500 worms).

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• Earthworms eat all kinds of food and yard wastes,
  including coffee grounds, tea bags, vegetable and
  fruit waste, pulverized egg shells, grass
  clippings, manure, and sewage sludge. Avoid
  bones, dairy products, and meats that may attract
  pests, and garlic, onions, and spicy foods.

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Methods of determination of groups earthworms
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The optimum conditions of growth E.foetida
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Why E.Foetida were used for composting?

• wide temperature range tolerance
• microbial activity greatly
• increase rates of mineralization
• high cellulase and lignolase activity
• digest long chains of polysaccharides
• removal of toxic metals
• breakdown of complex chemicals to non-toxic
  forms

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limitation vermicompost process

• not high enough for acceptable pathogen kill
• does not pass EPA rules for pathogen
  reduction

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Red Wigglers
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Backyard Compost
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Backyard Compost BinsGarden Gourmet
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Backyard Compost BinsSimple Bins
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Backyard Compost BinsTumbler
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Potentially toxic elements????5 ????? ?????
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