TECHNICAL UNIVERSITY OF GABROVO Department of Chemistry and Ecology

1. TECHNICAL UNIVERSITY OF GABROVO Department of Chemistry and Ecology AEROBIC BIODEGRADATION OF WASTE (COMPOSTING)

2. The prototype of the waste separationsystem…

3. Waste: “Waste, rubbish, trash, garbage, orjunk” isany unwanted or undesired material! • Any substance or object which the producer or the person in possession of it, discards or intends or is required to discard. • Waste can exist as: • solid; • liquid; • gas; • waste heat.

4. Waste hierarchy • The waste hierarchy refers to the "3 Rs“: • Reduce • Reuse • Recycle • They classify waste management strategies according to their desirability.

5. Recycling is a key concept of modern waste management and the third component of the waste hierarchy • Plastics • Metals • Glass • Paper RECYCLED WASTE: • Green waste • Food waste • Paper • Biodegradable plastics • Human waste • Manure • Sewage • Slaughterhouse waste BIODEGRADABLE WASTE:

6. WASTE HAS TO GOSOMEWHERE ! BUT WHERE ? INSTEAD OF HERE … Landfill.Unsightly. Unpopular. Unsustainable. Generating bio aerosols, offensive odor and landfill gas (methane). 21 times more powerful than carbon dioxide in terms of climate change effects! .

7. Incineration. There’s a place for it. But what placewants it? ‘Not in my backyard’. Moregases. Moreodor. More public distress. HERE …

8. Untreated waste spread on land. Imagine blood,guts and similar – spread or sprayed on fields –untreated. Since 2003, illegal. But it does happen OR HERE …

9. TREATED ORGANIC WASTE CAN SAFELY GO HERE … Agriculture. To enrich the earth…

10. HERE … Sport. To improve our recreational environment…

11. Horticulture. To give us pleasure… OR HERE…

12. July 2003EULandfill Directive and Animal By-Products (ABP) Regulationcame into force • NowMost organic waste iscurrently landfilleduntreated • In the close futurethe revised EU Sludge Directiveand the new Bio Waste Directive will both require organic waste to be treated!!!

13. Landfilling Anaerobic digestion: What is the answer? Methane (greenhouse gas) Aerobic decomposition (composting)

14. COMPOSTING • Composting is the process ofcontrolledaerobicdecomposition ofbiodegradableorganic matter • During composting, microorganisms break down organic matter into carbon dioxide, water, heat, and compost:

15. Materials for composting: • Food and drink industry waste; • Paper, card, timber and other biodegradable waste; • Household waste; • Organic sludge including sewage; • Agricultural waste. • : Wastes from meat, dairy products, and eggs should not be used in household compost: • they attract unwanted vermin; • they do not appropriately decompose in the time required.

16. Microorganisms are key to composting ! Main composting agents (decomposers) I. Microorganisms 1.1.Classification according to the O2 consuming: • Aerobic – use oxygen for their metabolism • Anaerobic– they are active in environment without oxygen

17. 1.2. Classification according to the thermal living conditions:

18. 1.3. Microorganisms growth during the composting process:

19. Heterotrophic Autotrophic Aerobic Anaerobic A. Bacteria • strong ability of growth in moist medium • large spectrum of activity • active in a large range of pH values • difficult to adapt in acid medium

20. B. Fungi Fermentingfungi Yeast • ability to live in medium with low moisture; • competitors of heterotrophic bacteria • active in a large range of pH: 2 – 9; • low requirements considering the nitrogen content

21. C. Actinomycetes • Aerobic and thermophilic; • They are assimilated by bacteria and fungi; • use organic nitrogen; • Active in neutral and slightly alkaline media; • Act in the ending phase of the composting process.

22. II. Other agents: • Duckweeds (algae) • Cyanophytes • Prothozoe • Enzymes

23. Stages of the composting process I. First stage: active (thermophilic) • performed by aerobic microorganisms; • decomposition of organic matter; (organic acids, aminoacids, saharides) occurs; • consuming of O2 and release of CO2 and energy; • high rate of composting process; • temperature - up to 55-60° С.

24. Temperature changing during the first stage for biomass with low and high degree of fermentation:

25. II. Second stage: cooling • Decomposing of more complicated organic molecules; • Most of the microorganisms die from lаck of “food”; • Lower rate of the process; • Temperature - up to 40-45° С; • Duration – few weeks :humification! Waste appearance before and after composting process

26. III. Third stage: maturation • Temperature is equal to the ambient; • A completely disinfected high quality compost is formed as a result

27. Composting Control parameters • Porosity of substrate (free volume) – defined by the spaces inside the biomass occupied by air and water. 1.1. General porosity Pg -the relation of empty spaces volume Vv and the whole biomass volume Vt: Pg = Vv / Vt , % 1.2. Free air space (FAS),Vf - the biomass volume, which is occupied by the air: • Porosity depends on: • Particle size distribution; • Level of humidity; • Height of the pail. (Vv –Va) / Vt Va – volume, occupied by water

28. 1. The particle size distribution, bulk density, and porosity of a compost mixture are group of factors that can lead to anaerobic conditions. 2. These physical characteristics of the compost mixture can interact with high moisture levels to reduce oxygen transport. Effective cross sectional area as a function of particle size distribution, shape, and packing density

29. 2. Moisture Water is one of the important elements for the microorganisms’ activity because: • is necessary for the nutrient substances exchange through the cell membrane; • forms transport medium for extracellular enzymes; • creates medium for soluble substances; • is important for chemical reactions performance < 40% moisture –degradation will proceed at a slow rate(under 25 -30% it stops); > 65% moisture - О2distributes very difficult in the biomass (anaerobic conditions established) Optimal moisture: 50 – 60%

30. The effect of aqueous film thickness on anaerobic odor production

31. Metabolic Regions as a function of moisture content

32. In a properly moist compost matrix, the particles (brown) are surrounded by aqueous films (blue), but are separated by air filled pores (white) Anaerobic zones (purple dots) are created as increasing water content fills small pores, so oxygen must diffuse farther through water.

33. 3. Quantity of oxygen C6H12O6 + 6O2→ 6CO2 + 6H2O + 2 800 KJ/mol To treat 1kgorganic matter 1,6 kg of O2are required ! • Oxygen requirement during the composting process: • First stage – 5-15% • Second stage – 1-5% • Air: 10 – 100 N.m3/h • O2 could be supplied by means of: • Mechanical mixing; • Forced ventilation (aeration ) Result: Complete mineralization? Humification? yes no

34. 4. Temperature: Temperature is a key parameter determining the success of composting process! Heat is produced as a by-product of the microbial breakdown of organic material • Defines the thermophilic stage of the composting process; • Easy to monitor • Provides disinfection of the product - at 55C almost all pathogenic are killed; • Kills the weeds’ seeds at 65C and more : t > 70C kills also bacteria responsible for composting process! First stage: 55-65C Second stage: 35 - 45C t< 25C end of the composting process Values of released energy for main substances: Glucosis 19 kJ/g Lipides 39 kJ/g Proteines 23 kJ/g M. KolevaERASMUS’07

35. Temperature and pH profiles during composting

36. 5. Ratio C/N, C/P and C/S  naturally existing in biomass C,N,P,K 4.1. C/N: 30 atoms C : 1 atom N Important: balanced ratio C/N C – source of energy for heterotrophic microorganisms; N – important for syntesis of protheins • Excess of N that leads to release of NH3 • NH3 is stimulated by:  t ,  N, pH C/N < 30 1/3 used by microorganisms C 2/3 converted to CO2 • Inhibited decomposing process; • Increased composting time • Optimal ratio C/N: • at the start 25 -30 • At the end < 20 (10:1) C/N > 30 Carbon-to-nitrogen ratios may need to be adjusted depending on thebioavailability of these elements !!! 4.2. C/P: P acts as a catalyst of biochemical reactions! Optimal ratio: 100 < C/P< 200 4.3. C/S: Optimal ratio: 100 < C/S< 300

37. Typical C/N ratios for common compost materials Source: Dickson, N., T. Richard, and R. Kozlowski. 1991. Composting to Reduce the Waste Stream: A Guide to Small Scale Food and Yard Waste Composting

38. 6. pH I st period:pH value decreases The reason: generation of CO2 II nd period:pH value increases up to 8-9 The reason:generation of NH3 • Optimal values of pH are: • at the beginning pH 5.5  8 • at the end: pH  7 Compost microorganisms operate best under neutral to acidic conditions! pH max  8.5

39. Let’s summarize : Factors Leading to Anaerobic Conditions 1. Inadequate porosity Oxygen is consumed much more rapidly 3. Excess moisture oxygen cannotmove into a pile 2. Excessive pile size the correct pile size balances the heat generated by microbial decomposition 4. Rapidly degrading substrate reduces oxygen penetration

40. Compost Compost isthe aerobicallydecompo-sed remnants of organic materials Compost is used: • in gardening and agriculture as a soil amendment; • for erosion control, land/stream reclamation, wetland construction, and as landfill cover; • as a seed starting medium generally mixed with a small portion of sand for improved drainage

41. There are several ways to determine the degree of compost’s stability achieved: • Oxygen uptake rate. • Low degree of reheating incuring piles. • Organic content of thecompost. • Presence of nitrates and the absence ofammonia and starch in the compost. • Indexes of compost stability: • Germination index (GI):shows the presence of phytotoxic substances in compost: • Compost is phytotoxic if GI > 30% • Nitrogen mineralization index (NMI): Based on the valuation of organic nitrogen biodegradation: • For mature compost NMI < 3.5%! • Respiration index (RI):Based on the consumption of O2: • the higher the RI, the lower the compost stability; FINISHED COMPOSTPRODUCT • Humification index (HI): HI = NH/ (HA+FA) • NH- non humified fraction; HA – humic acids; FA – fulvic acids M. KolevaERASMUS’07

42. Composting technics and equipment

43. Types of composting 1. According to the method of aerobic composting: B. Passive (or cold) composting A. Active (or hot) composting • allows aerobic bacteria to thrive • kills most pathogens and seeds • Aerobic bacteria produce less odour and fewer destructive greenhouse gases than their anaerobic ; • temperature reachesabove 55°C (131°F) • more slow than the hot one; • many pathogens and seedsdormant in the pile; • done in most domestic garden; • temperatures never reach above 30°C (86°F) 2. According to the technical performance: A. Enclosed: B. In exposed piles • home container composting; • industrial in-vessel composting) • industrial windrow composting

44. Home container composting

45. Industrial In-vessel composting Types of in-vessel compostingreactors: • vertical plug-flow • horizontal plug-flow • agitated bin Flow diagram of a typical in-vessel composting facility

46. BioChamber™ • Fully-enclosed, automated, thermophilic composting • Capable of processing between 1 and 800 or more* tons/day • Modular, scalable, stackable design • Accelerates waste conversion through effective monitoring of temperature, oxygen  and moisture levels • Programmable 7 - 21 day waste stabilization time • Advanced remote monitoring and control • Strict odor control and captures 100% of all leachate for beneficial reuse • Effective elimination of pathogens and weed seeds • Elimination of vectors (rats, bugs, birds, etc.) as required by law • Smallest footprint and lowest cost per/ton processing capacity in the industry • Ideal for both urban and rural settings Aself-contained, automated, in-vessel thermophilic composting system designed to convert food waste (including meat, dairy & fish waste), animal manure, sewage sludge (biosolids) and other biodegradable waste

47. BioTower™ (BioSystem Solutions, • Advanced"Smart-Silo" ThermophilicVerticalComposting System • Utilizing less space per processing • provides automated loading, turning and compost discharge to reduce labor cost and increase worker safety

48. Containerized in-vessel drum compostsystems(Willcam Inc., USA) • daily output volumes: 16, 35 or 50 cubic yards

49. Containerized Stationary • Stationary and containerized in-vessel compost systems(Engineered Compost Systems, USA) • processing 1 to 200 tons per day ; • computer controlled aeration system • minimized odor generation

50. In-vessel composting • Advantages • The composting process can be more closelycontrolled. • The effects of weather are diminished. • Less bulking agent may be required. • The quality of the resulting product is moreconsistent. • Less manpower is required tooperate thesystem and staff is less exposed to thecomposting material. • Process air can be more easily collected fortreatment to reduce odor emissions. • Less land area is required. • Public acceptance of the facility may bebetter. ? Yes not or • Disadvantages • In-vessel composting is generallymore costly than other composting methods. • Moreequipment maintenance isnecessary. • Thelarge amount of carbonaceous materialcreates thepotential forfires in storage areas as well as in the activecomposting mass.