TECHNICAL UNIVERSITY OF GABROVO Department of Chemistry and

TECHNICAL UNIVERSITY OF GABROVO Department of Chemistry and Ecology

The prototype of the waste separation system…

“Waste, rubbish, trash, garbage, or junk” is any 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.

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

Recycling is a key concept of modern waste management and the third component of the waste hierarchy Plastics Metals Glass Paper Green waste Food waste Paper Biodegradable plastics Human waste Manure Sewage Slaughterhouse waste

WASTE HAS TO GO SOMEWHERE ! 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!

HERE … Incineration. There’s a place for it. But what place wants it? ‘Not in my backyard’. More gases. More odor. More public distress.

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 …

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

HERE … Sport. To improve our recreational environment…

OR HERE… Horticulture. To give us pleasure…

July 2003 EU Landfill Directive and Animal By-Products (ABP) Regulation came into force Now Most organic waste is currently landfilled untreated In the close future the revised EU Sludge Directive and the new Bio Waste Directive will both require organic waste to be treated!!!

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

Composting is the process of controlled aerobic decomposition of biodegradable organic matter During composting, microorganisms break down organic matter into carbon dioxide, water, heat, and compost:

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.

Main composting agents (decomposers) Microorganisms are key to composting ! I. Microorganisms 1. 1. Classification according to the O 2 consuming: Aerobic – use oxygen for their metabolism Anaerobic– they are active in environment without oxygen

1. 2. Classification according to thermal living conditions: Temperatu Microorg re range anisms of activity, о. С Ø Psychr ophiles 0 - 30 Ø Mesop 30 – 45 hiles 45 – 50 Ø Therm ophiles

1. 3. Microorganisms growth during the composting process: Microorganism s Populations according to thermal conditions <40 о. С 40 70 о. С 108 104 106 109 104 108 106 103 107 BACTERI A Mesophiles Thermophiles ACTINOMI CETES Thermophiles FUNGI Mesophiles Thermophiles

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

B. Fungi Fermenting fungi Yeast ability to live in medium with low moisture; competitors of heterotrophic bacteria active in a large range of p. H: 2 – 9; low requirements considering the nitrogen content

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.

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

I. First stage: active (thermophilic) performed by aerobic microorganisms; decomposition of organic matter; (organic acids, aminoacids, saharides) occurs; consuming of O 2 and release of CO 2 and energy; high rate of composting process; temperature - up to 55 -60° С.

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

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

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

Composting Control parameters 1. 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: (Vv –Va) / Vt Particle size distribution; Va – volume, Level of humidity; occupied by water Height of the pail.

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

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

The effect of aqueous film thickness on anaerobic odor production

Metabolic Regions as a function of moisture content

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.

3. Quantity of oxygen C 6 H 12 O 6 + 6 O 2 → 6 CO 2 + 6 H 2 O + 2 800 KJ/mol To treat 1 kg organic matter 1, 6 kg of O 2 are required ! Oxygen requirement during O 2 could be supplied the composting process: First stage – 5 - 15% Second stage – 1 - 5% Air: 10 – 100 N. m 3/h by means of: Mechanical mixing; Forced ventilation (aeration ) Result: Complete mineralization? Humification?

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 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 First stage: 55 -65 C responsible for composting process! Second stage: 35 - 45 C Values of released energy for main substances: t< 25 C end of the composting process 19 k. J/g Lipides M. Koleva ERASMUS’ 07 Glucosis 39 k. J/g Proteines 23 k. J/g

Temperature and p. H profiles during composting

5. Ratio C/N, C/P and C/S naturally existing in biomass 4. 1. C/N: Importan t: balanc ed ratio C /N 30 atoms C : 1 atom N C – source of energy for heterotrophic microorganisms; N – important for syntesis of protheins C 1/3 used by microorganisms 2/3 converted to CO 2 C/N > 30 ng composi ed de • Inhibit process; ing compost ed • Increas time • Excess of N that leads to release of NH 3 C/N < 30 • NH 3 is stimulated by: t , N, p. H Carbon-to-nitrogen ratios may need to be adjusted Optimal ratio C/N: • at the start 25 -30 • At the end < 20 (10: 1) depending on the bioavailability 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

Typical C/N ratios for common compost materials Materials High in Carbon C/N* autumn leaves 30 -80: 1 straw 40 -100: 1 wood chips or sawdust 100 -500: 1 bark 100 -130: 1 mixed paper 150 -200: 1 newspaper or corrugated cardboard 560: 1 Materials High in Nitrogen C: N* vegetable scraps 15 -20: 1 coffee grounds 20: 1 grass clippings 15 -25: 1 manure 5 -25: 1 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

6. p. H I st period: p. H value decreases The reason: generation of CO 2 II nd period: p. H value increases up to 8 -9 The reason: generation of NH 3 Compost microorganisms operate best under neutral to acidic conditions! Optimal values of p. H are: at the beginning p. H 5. 5 8 at the end: p. H 7 p. H max 8. 5

Factors Leading to Anaerobic Conditions 1. Inadequate porosity oxygen cannot move into a pile 2. Excessive pile size the correct pile size balances the heat generated by microbial decomposition 3. Excess moisture reduces oxygen penetration Oxygen is consumed much more rapidly 4. Rapidly degrading substrate

Compost is the aerobically decomposed 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

There are several ways to determine the degree of compost’s stability achieved: Indexes of compost stability: Germination index (GI): • Oxygen uptake rate. shows the presence of phytotoxic • Low degree of reheating in curing substances in compost: piles. • Organic content of the compost. Compost is phytotoxic if GI > 30% • Presence of nitrates and the absence of ammonia and starch in the Nitrogen mineralization compost. index (NMI): Based on the valuation of organic nitrogen biodegradation: For mature compost NMI < 3. 5%! Respiration index (RI): Based on the consumption of O 2: FINISHED COMPOST PRODUCT the higher the RI, the lower the compost stability; Humification index (HI): HI = NH/ (HA+FA) NH- non humified fraction; HA – humic acids; FA – fulvic acids M. Koleva ERASMUS’ 07

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 reaches above 55°C (131°F) more slow than the hot one; many pathogens and seeds dormant in the pile; done in most domestic garden; temperatures never reach above 30°C (86°F) 2. According to the technical performance: A. Enclosed: home container composting; industrial in-vessel composting) B. In exposed piles industrial windrow composting

Home container composting

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

Bio. Chamber™ A self-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 • 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

Bio. Tower™ (Bio. System Solutions, • Advanced "Smart-Silo" Thermophilic Vertical Composting System • Utilizing less space per processing • provides automated loading, turning and compost discharge to reduce labor cost and increase worker safety

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

Containerized 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

Advantages The composting process can be more closely controlled. The effects of weather are diminished. Less bulking agent may be required. The quality of the resulting product is more consistent. Less manpower is required to operate the system and staff is less exposed to the composting material. Process air can be more easily collected for treatment to reduce odor emissions. Less land area is required. Public acceptance of the facility may be better. or ? Disadvantages In-vessel composting is generally more costly than other composting methods. More equipment maintenance is necessary. The large amount of carbonaceous material creates the potential for fires in storage areas as well as in the active composting mass.

Industrial Windrow composting Benefits: Compost reduces the amount of waste to be disposed. Easy to use and operate. Can handle a large volume of material. Low operating costs. Less equipment and maintenance needed than other methods. WT-3000 Water Trailer (Midwest Bio-Systems, USA) PT-120 10 foot Pull-type Compost Turner (Midwest Bio-Systems, USA) Disadvantages: Large amount of land for composting. May attracts scavengers. Odors may be produced. Requires large adjacent areas due to odor and vectors. Rainwater runoff maintenance. Compost can become anaerobic under rainy conditions.

Increases water holding capacity. Increases aeration and drainage for clay soils. Provides organic nitrogen, phosphorus, and potassium. Provides essential plant micronutrients. Can reduce the need for pesticides. Composting is an environmentally beneficial activity !