Managing Organic Wastes By Composting and Vermicomposting

1
Managing Organic Wastes By Composting and
Vermicomposting

• DENR Environmental Education Workshop
• November 16, 1999
• Presenter Craig Coker, Division of Pollution
  Prevention Environmental Assistance

2
PRINCIPLES OFCOMPOSTING
3
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

4
Why Compost?

• gt 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

5
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

6
Composting Essential Elements

• Nutrients
• Carbon/Nitrogen (C/N) 201 to 351
• Carbon/Phosphorus (C/P) 1001 to 1501
• 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 - gt5
• Temperature 130o F. to 150o F.
• Time one to four months

7
Nutrient Balance in Composting

• C/N ratio target is 301
• gt 301 not enough food for microbial population
• lt 301 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

8
Moisture Content

• Source of nutrients for microbial protein
  synthesis and growth
• Optimum water content 50 to 60 (wet weight
  basis)
• lt 50 - composting slows due to microbial
  dessication
• gt60 - 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

9
Particle Size Distribution

• Critical for balancing
• Surface area for growth of microbes (biofilm)
• Adequate porosity for aeration (35 - 50)
• Larger particles (gt 1)
• Lower surface area to mass ratio
• Particle interior doesnt compost lack of
  oxygen
• Smaller particles (lt 1/8)
• Tend to pack and compact
• Inhibit air flow through pile
• Optimum size very material specific

10
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 gt 5
• Above pH 8.0
• Ammonia gas can be generated
• Microbial populations decline

11
Porosity and Aeration

• Optimum porosity 35 - 50
• gt 50 - energy lost is greater than heat produced
  ?lower temperatures in compost pile
• lt 35 - anaerobic conditions (odors)
• Aeration controls temperatures, removes
  moisture and CO2 and provides oxygen
• Airflow needs directly proportional to biological
  activity
• O2 concentration lt 5 - anaerobic conditions

12
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 gt 131o F. for 15 days in windrows
• Temperatures gt 131o F. for 3 days in ASP or
  invessel
• Optimum temps achieved by regulating airflow
  (turning) and/or pile size

13
Time and Temperature, cont.
14
Time and Temperature, cont.
15
COMPOSTINGTECHNOLOGIES
16
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)

17
Types of BYC Systems
18
Types of BYC Systems
19
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

20
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

21
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

22
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

23
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

24
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

25
Institutional Composting
Worm Wigwam (small)
Worm Wigwam (large)
26
Institutional Composting
Rotary Drum
Earth Tub
27
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)

28
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

29
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)

30
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

31
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

32
Aerated Compost Bins
33
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

34
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

35
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

36
In-Vessel Composting

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

37
In-Vessel Composting
38
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

39
Benefits of Compost Utilization
40
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

41
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 VOCs in exhaust gases

42
Typical Compost Characteristics
43
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

44
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 engineeringCOMPOST HAPPENS!