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Managing Organic Wastes By Composting and Vermicomposting. DENR Environmental Education Workshop November 16, 1999 Presenter: Craig Coker, Division of Pollution Prevention & Environmental Assistance. PRINCIPLES OF COMPOSTING. Principles of Composting. What Is Compost?

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managing organic wastes by composting and vermicomposting

Managing Organic Wastes By Composting and Vermicomposting

DENR Environmental Education Workshop

November 16, 1999

Presenter: Craig Coker, Division of Pollution Prevention & Environmental Assistance

principles of composting3
Principles of Composting
  • What Is Compost?
    • The product resulting from the controlled biological decomposition of organic materials
    • Sanitized through the generation of heat
    • Stabilized to the point where it is beneficial to plant growth
    • Provides humus, nutrients, and trace elements to soils
  • Organic Materials
    • Landfilled wastes (food, wood, textiles, sludges, etc.)
    • Agricultural wastes (plant or animal)
    • Industrial manufacturing byproducts
    • Yard trimmings
    • Seafood processing wastes
    • In short, anything that can be biodegraded
why compost
Why Compost?
  • > 75% of solid waste in NC is organic
  • 12% of landfilled solid waste in NC in 1998 was food wastes/discards
  • Agricultural wastes  potential for nutrient pollution
  • Yard wastes – banned from landfills in 1993
  • Compost benefits to soil – 25 lbs N, 13 lbs P (as P2O5), and 7 lbs K (as K2O) per ton of compost
  • Environmental sustainability
the composting process
The Composting Process
  • Biological decomposition in aerobic environment
  • Decomposition & mineralization by microbes
    • Bacteria, actinomycetes, fungi, protozoans, nematodes
    • Food source – Nitrogen (biodegradable organic matter)
    • Energy source – Carbon (bulking agent)
  • Outputs
    • Heat
    • Water Vapor
    • Carbon Dioxide
    • Nutrients and minerals (compost)
  • Process occurs naturally, but can be accelerated by controlling essential elements
composting essential elements
Composting Essential Elements
  • Nutrients
    • Carbon/Nitrogen (C/N) – 20:1 to 35:1
    • Carbon/Phosphorus (C/P) – 100:1 to 150:1
  • Moisture Content – 50% to 60% (wet basis)
  • Particle Size – ¼” to ¾” optimum
  • Porosity – 35% to 50%
  • pH – 6.5 to 8.0
  • Oxygen concentration - >5%
  • Temperature – 130o F. to 150o F.
  • Time – one to four months
nutrient balance in composting
Nutrient Balance in Composting
  • C/N ratio – target is 30:1
    • > 30:1 – not enough food for microbial population
    • < 30:1 – nitrogen lost as ammonia (odors)
  • Sources of N & P - Organic wastes, manures, sludges, etc.
  • Sources of C – wood wastes, woodchips, sawdust
  • Example C/N Ratios:
    • Food waste 14 – 16 : 1
    • Refuse/trash 34 –80 : 1
    • Sewage sludge 5 –16 : 1
    • Corrugated cardboard 563 : 1
    • Telephone books 772 : 1
  • Mixing components needed to optimize C/N ratio
moisture content
Moisture Content
  • Source of nutrients for microbial protein synthesis and growth
  • Optimum water content – 50% to 60% (wet weight basis)
    • < 50% - composting slows due to microbial dessication
    • >60% - compaction, development of anaerobic conditions, putrefaction/fermentation (odors)
  • Water may be needed during mixing, composting
    • Yard wastes – 40 to 60 gallons per cubic yard
  • Typical moisture contents
    • Food wastes 70%
    • Manures and sludges 72% - 84%
    • Sawdust 19% - 65%
    • Corrugated cardboard 8%
    • Newsprint 3% - 8%
particle size distribution
Particle Size & Distribution
  • Critical for balancing:
    • Surface area for growth of microbes (biofilm)
    • Adequate porosity for aeration (35% - 50%)
  • Larger particles (> 1”)
    • Lower surface area to mass ratio
    • Particle interior doesn’t compost – lack of oxygen
  • Smaller particles (< 1/8”)
    • Tend to pack and compact
    • Inhibit air flow through pile
  • Optimum size very material specific
slide10
pH
  • Optimum range 6.5 – 8.0
    • Bacterial activity dominates
  • Below pH = 6.5
    • Fungi dominate over bacteria
    • Composting can be inhibited
    • Avoid by keeping O2 > 5%
  • Above pH – 8.0
    • Ammonia gas can be generated
    • Microbial populations decline
porosity and aeration
Porosity and Aeration
  • Optimum porosity 35% - 50%
    • > 50% - energy lost is greater than heat produced lower temperatures in compost pile
    • < 35% - anaerobic conditions (odors)
  • Aeration – controls temperatures, removes moisture and CO2 and provides oxygen
    • Airflow needs directly proportional to biological activity
    • O2 concentration < 5% - anaerobic conditions
time and temperature
Time and Temperature
  • Temperature is key process control factor – monitor closely
  • Optimum temperatures: 130o F. – 150o F.
  • Temperatures above 131o F. (55o C.) will kill pathogens, fecal coliform & parasites
  • NC Regulations (BYC, small yard waste and on-farm exempt)
    • Temperatures > 131o F. for 15 days in windrows
    • Temperatures > 131o F. for 3 days in ASP or invessel
  • Optimum temps achieved by regulating airflow (turning) and/or pile size
backyard composting
Backyard Composting
  • Potential diversion – 400 – 800 lbs/year/household
  • Suitable materials
    • Yard trimmings (leaves, grass, shrubs)
    • Food wastes (produce, coffee grounds, eggshells)
    • Newspaper
  • Unsuitable materials
    • Pet wastes
    • Animal remains (meat, fish, bones, grease, whole eggs, dairy products)
    • Charcoal ashes
    • Invasive weeds and plants (kudzu, ivy, Bermudagrass)
backyard composting easy to do
Backyard Composting – Easy To Do!
  • Locate in flat area, shielded from sun & wind
  • Add materials in layers (browns/greens)
  • Turn pile after 1st week, then 2-3 times over next two months
backyard composting cont
Backyard Composting, cont.
  • Can add fresh wastes when turning, but better to start new pile
  • Compost will be ready to use in
    • 4 – 6 months for piles started in Spring
    • 6 – 8 months for piles started in Fall
  • Troubleshooting – see Handout
vermicomposting home wastes
Vermicomposting Home Wastes
  • Vermicompost = worm castings + bedding
  • Nutrient Value - 6600 ppm organic nitrogen, 1300 ppm phosphorus & 1,000 ppm potassium
  • What to feed worms –
    • Vegetable scraps, breads and grains
    • Fruit rinds and peels
    • Tea bags, coffee grounds, coffee filters, etc.
  • What not to feed worms –
    • Meat, fish, cheese or butter
    • Greasy, oily foods
    • Animal wastes
vermicomposting how to do it
Vermicomposting – How To Do It
  • Bin – wooden, plastic or metal with tight-fitting lid
    • 2’ x 3’ x 1’ – good for 2-3 person household
    • Need drainage holes in bottom and air vents on top and sides
vermicomposting how to do it23
Vermicomposting – How to do it
  • Add moist drained bedding to worm bin
    • 1” – 2” strips of newspaper/cardboard/leaves/peat moss/sawdust
    • Fill bin with bedding
  • Start with 2 lbs of redworms/lb daily scraps
    • Eisenia foetida or Lumbricus rubellus
  • Bury food scraps under 4 – 6” bedding
    • Rotate burial around bin to prevent overloading
  • Harvest vermicompost in 3 – 6 months
institutional composting
Institutional Composting
  • University dining halls
  • Industrial/government cafeterias
  • Current programs in North Carolina
    • UNC – Asheville (Earth Tub)
    • UNC – Charlotte (Earth Tub – next year)
    • NIEHS (Worm Wigwam)
    • DENR/Archdale Cafeteria
    • Sampson Correctional Institution (Worm Wigwam)
    • Brown Creek Correctional (Rotary Drum Composter)
    • Several small schoolroom vermicomposting systems
institutional composting25
Institutional Composting

Worm Wigwam (small)

Worm Wigwam (large)

institutional composting26
Institutional Composting

Rotary Drum

Earth Tub

institutional composting27
Institutional Composting
  • Key is efficient source separation of organics
  • Separate collection containers from regular trash
  • Training needed to minimize contaminants (non-compostables like plastics, foils, metals)
commercial composting
Commercial Composting
  • Larger-scale commercial and municipal facilities
  • Feedstocks: manures, agricultural wastes (I.e. cotton gin trash), industrial and municipal wastewater treatment sludges, food wastes
  • Technologies used:
    • Windrows
    • Aerated Compost Bins
    • Aerated Static Pile
    • In-Vessel Systems
  • Produced compost sold for $18 - $20/yd3
slide29

Overview

  • Technology in Composting
    • Materials Handling
    • Biological Process Optimization
    • Odor Control
  • Capital Cost
    • Increases with technology
  • Operational Costs
    • Decrease with technology
  • Footprint (Area Required)
    • Decreases with technology (usually)
windrow composting
Windrow Composting
  • Materials mixed and formed into windrows
  • Windrows 7’ –8’ wide, 5’ – 6’ tall, varying lengths
  • Compost turned and mixed periodically
  • Aeration by natural/passive air movement
  • Composting time : 3 – 6 months
slide31

Windrow Composting, cont.

  • Equipment Needed
    • Grinder/Shredder
    • Tractor/FEL
    • Windrow Turner
      • tractor-pulled
      • self-propelled
    • Screener
  • One Acre Can Handle 4,000 - 7,000 CY Compost Mix
slide33

Aerated Compost Bins

  • Aeration through porous floor plates
  • Composting time : 2 - 3 weeks
  • Curing time : 2 months
  • Durable materials of construction
  • Equipment needed : front end loader
  • Vector/vermin control needed with food wastes
  • Capacities : 3 - 4 days food waste + bulking agent per bin
aerated static pile composting
Aerated Static Pile Composting
  • Mixed materials built on bed with aeration pipes embedded
  • Aeration by mechanical blowers
  • Composting for 21 days, followed by curing for 30 days
  • Often used in biosolids (sludge) composting
slide35

Aerated Static Pile

  • Better suited to larger volumes (landscape debris, sludges)
  • Shorter processing time than with windrows
  • May not be suited to wastes that need mixing during composting, like food wastes
  • Difficult to adjust moisture content during composting if needed
  • Odor control difficult with positive aeration
  • Less land area than windrows, still labor intensive
in vessel composting
In-Vessel Composting
  • More mechanically complex
  • More expensive
  • Smaller footprint (area)
  • Relatively high operations & maintenance costs
commercial composting in nc
Commercial Composting in NC
  • Brooks Contractors, Goldston, NC
    • Windrow composting – eggshells, food waste, yard wastes, cardboard
  • McGill Environmental, Rose Hill, NC
    • Aerated static pile – biosolids, industrial food processing residues, furniture wastes
  • Progressive Soil Farms, Welcome, NC
    • Windrow composting – textile wastes, yard wastes
  • City of Hickory, NC
    • In-vessel composting – biosolids, sawdust
  • Mountain Organic Materials, Asheville, NC
    • Aerated compost bins – manures and sawmill wastes
  • Others: Lenoir, Morganton, Shelby
compost benefits
Compost Benefits
  • Physical Benefits
    • Improved soil structure, reduced density, increased permeability (less erosion potential)
    • Resists compaction, increased water holding capacity
  • Chemical Benefits
    • Modifies and stabilizes pH
    • Increases cation exchange capacity (enables soils to retain nutrients longer, reduces nutrient leaching)
  • Biological Benefits
    • Provides soil biota – healthier soils
    • Suppresses plant diseases
more compost benefits
More Compost Benefits
  • Binds heavy metals and other contaminants, reducing leachability and bioabsorption
  • Degrades petroleum contaminants in soils
  • Enhances wetlands restoration by simulating the characteristics of wetland soils
  • Coarser composts used as mulch provide erosion control
  • Can provide filtration and contaminant removal of stormwater pollutants
  • Biofiltration of VOC’s in exhaust gases
compost utilization examples
Compost Utilization Examples
  • Planting Bed Establishment
    • Apply 3 – 6 yd3 per 1000 sq. feet
    • Rototill to depth of 6 – 8”
    • Mulch and water after plants installed
  • Turfgrass Establishment
    • Apply 2” – 3” layer of compost to soil
    • Rototill 6 – 8” deep
    • Rake smooth, lay sod or spread seed
    • Apply starter fertilizer and/or water as needed
  • Compost Used For Bedding Mulch
    • 2” – 3” layer installed before mulching with pine bark or hardwood bark mulch
summary
Summary
  • Composting is an effective way to manage organic wastes
  • Composting promotes environmental sustainability by converting a waste to a value-added product that improves our environment
  • Composting can be done at home, at school or at work, and by commercial and municipal entities
  • Composting is a mix of the art of the gardener, the science of horticulture, and the discipline of waste engineering…COMPOST HAPPENS!