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? • > 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) – 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

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 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) • < 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%

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 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

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 > 5% • Above pH – 8.0 • Ammonia gas can be generated • Microbial populations decline

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 CO2 and provides oxygen • Airflow needs directly proportional to biological activity • O2 concentration < 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 > 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

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 VOC’s 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 engineering…COMPOST HAPPENS!