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Download Managing Organic Wastes By Composting and Vermicomposting DENR Environmental Education Workshop November 16, 1999 Presenter: Craig Coker, Division of Pollution

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  • Slide 1
  • Managing Organic Wastes By Composting and Vermicomposting DENR Environmental Education Workshop November 16, 1999 Presenter: Craig Coker, Division of Pollution Prevention & Environmental Assistance
  • Slide 2
  • PRINCIPLES OF COMPOSTING
  • Slide 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
  • Slide 4
  • 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 P 2 O 5 ), and 7 lbs K (as K 2 O) per ton of compost Environmental sustainability
  • Slide 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
  • Slide 6
  • 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 to optimum Porosity 35% to 50% pH 6.5 to 8.0 Oxygen concentration - >5% Temperature 130 o F. to 150 o F. Time one to four months
  • Slide 7
  • 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 waste14 16 : 1 Refuse/trash34 80 : 1 Sewage sludge 5 16 : 1 Corrugated cardboard 563 : 1 Telephone books 772 : 1 Mixing components needed to optimize C/N ratio
  • Slide 8
  • 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 wastes70% Manures and sludges72% - 84% Sawdust 19% - 65% Corrugated cardboard 8% Newsprint 3% - 8%
  • Slide 9
  • 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 doesnt compost lack of oxygen Smaller particles (< 1/8) Tend to pack and compact Inhibit air flow through pile Optimum size very material specific
  • Slide 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 O 2 > 5% Above pH 8.0 Ammonia gas can be generated Microbial populations decline
  • Slide 11
  • 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 CO 2 and provides oxygen Airflow needs directly proportional to biological activity O2 concentration < 5% - anaerobic conditions
  • Slide 12
  • Time and Temperature Temperature is key process control factor monitor closely Optimum temperatures: 130 o F. 150 o F. Temperatures above 131 o F. (55 o C.) will kill pathogens, fecal coliform & parasites NC Regulations (BYC, small yard waste and on-farm exempt) Temperatures > 131 o F. for 15 days in windrows Temperatures > 131 o F. for 3 days in ASP or invessel Optimum temps achieved by regulating airflow (turning) and/or pile size
  • Slide 13
  • Time and Temperature, cont.
  • Slide 14
  • Slide 15
  • COMPOSTING TECHNOLOGIES
  • Slide 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)
  • Slide 17
  • Types of BYC Systems
  • Slide 18
  • Slide 19
  • Backyard Composting Easy To Do! Locate in flat area, shielded from sun & wind Add materials in layers (browns/greens) Turn pile after 1 st week, then 2-3 times over next two months
  • Slide 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
  • Slide 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
  • Slide 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
  • Slide 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
  • Slide 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
  • Slide 25
  • Institutional Composting Worm Wigwam (small) Worm Wigwam (large)
  • Slide 26
  • Institutional Composting Rotary Drum Earth Tub
  • Slide 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)
  • Slide 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/yd 3
  • Slide 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)
  • Slide 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
  • Slide 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
  • Slide 32
  • Aerated Compost Bins
  • Slide 33
  • 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
  • Slide 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
  • Slide 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
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