“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.
Plastics Metals Glass Paper Green waste Food waste Paper Biodegradable plastics Human waste Manure Sewage Slaughterhouse waste Recycling is a key concept of modern waste management and the third component of the waste hierarchy
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!.
Incineration. There’s a place for it. But what place wants it? ‘Not in my backyard’. More gases. More odor. More public distress. HERE …
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…
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!!!
What is the answer? Anaerobic digestion: Aerobic decomposition (composting) Landfilling Methane (greenhouse gas)
Composting is the process of controlled aerobic decomposition of biodegradable organic matter aerobicbiodegradable 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:meatdairy productseggs they attract unwanted vermin; they do not appropriately decompose in the time required.
Main composting agents (decomposers) 1.1. Classification according to the O 2 consuming: Aerobic – use oxygen for their metabolism Anaerobic– they are active in environment without oxygen Microorganisms are key to composting ! I. Microorganisms
1.2. Classification according to the thermal living conditions: Microorganisms Temperature range of activity, о С Psychrophiles Mesophiles Thermophiles 0 - 30 30 – 45 45 – 50
1.3. Microorganisms growth during the composting process: Microorganisms Populations according to the thermal conditions <40 о С 40 - 70 о С BACTERIA Mesophiles Thermophiles ACTINOMICETES Thermophiles FUNGI Mesophiles Thermophiles 10 8 10 4 10 6 10 9 10 8 10 3 10 7
A. A. Bacteria Heterotrophic Autotrophic Aerobic Anaerobic 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
B. Fungi 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 Fermenting fungi Yeast
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
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. I. First stage: active (thermophilic)
Temperature changing during the first stage for biomass with low and high degree of fermentation:
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 II. Second stage: cooling
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. Pg = Vv / Vt, % Vf 1.2. Free air space (FAS), Vf - the biomass volume, which is occupied by the air: (Vv –Va) / Vt Va – volume, occupied by water Porosity depends on: Particle size distribution; Level of humidity; Height of the pail. 1.1. General porosity Pg - the relation of empty spaces volume Vv and the whole biomass volume Vt:
Effective cross sectional area as a function of particle size distribution, shape, and packing density 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.
2. Moisture 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 Optimal moisture: 50 – 60% < 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) Water is one of the important elements for the microorganisms’ activity because:
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 + 6O 2 → 6CO 2 + 6H 2 O + 2 800 KJ/mol To treat 1kg organic matter 1,6 kg of O 2 are required ! Oxygen requirement during the composting process: First stage – 5 - 15% Second stage – 1 - 5% Air: 10 – 100 N.m 3 /h O 2 could be supplied by means of: Mechanical mixing; Forced ventilation (aeration ) Complete mineralization? Humification? Result:
4. Temperature: : t > 70 C kills also bacteria responsible for composting process! 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 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 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 M. Koleva ERASMUS’07
5. Ratio C/N, C/P and C/S naturally existing in biomass naturally existing in biomass 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 30 atoms C : 1 atom N C/N > 30 Inhibited decomposing process; Increased composting time C/N < 30 Excess of N that leads to release of NH 3 NH 3 is stimulated by: t, N, pH 4.1. C/N: Important: balanced ratio C/N 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 Optimal ratio C/N: at the start 25 -30 At the end < 20 (10:1) Carbon-to-nitrogen ratios may need to be adjusted depending on the bioavailability of these elements !!!
Materials High in CarbonC/N* autumn leaves30-80:1 straw40-100:1 wood chips or sawdust100-500:1 bark100-130:1 mixed paper150-200:1 newspaper or corrugated cardboard560:1 Materials High in NitrogenC:N* vegetable scraps15-20:1 coffee grounds20:1 grass clippings15-25:1 manure5-25:1 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
6. pH : I st period: pH value decreases The reason: generation of CO 2 II nd period: pH value increases up to 8-9 The reason: generation of NH 3 Optimal values of pH are: at the beginning pH 5.5 8 at the end: pH 7 pH max 8.5 Compost microorganisms operate best under neutral to acidic conditions!
Factors Leading to Anaerobic Conditions 1. Inadequate porosity 3. Excess moisture 4. Rapidly degrading substrate 2. Excessive pile size oxygen cannot move into a pile the correct pile size balances the heat generated by microbial decomposition reduces oxygen penetration Oxygen is consumed much more rapidly
Compost is the aerobically decompo- sed remnants of organic materials 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 Compost is used:
There are several ways to determine the degree of compost’s stability achieved: Oxygen uptake rate. Low degree of reheating in curing piles. Organic content of the compost. Presence of nitrates and the absence of ammonia and starch in the compost. FINISHED COMPOST PRODUCT 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 O 2: 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: A. Active (or hot) composting B. Passive (or cold) composting allows aerobic bacteria to thrive kills most pathogens and seeds Aerobic bacteria produce less odour and fewer destructive greenhouse gases than their anaerobic ; greenhouse gases 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: home container composting;container composting industrial in-vessel composting)in-vessel composting industrial windrow compostingwindrow composting A. Enclosed:B. In exposed piles
Flow diagram of a typical in-vessel composting facility vertical plug-flow horizontal plug-flow agitated bin Types of in-vessel composting reactors: Industrial In-vessel composting
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 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
Advanced "Smart-Silo" Thermophilic Vertical Composting System BioTower™ ( BioSystem Solutions, 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
Stationary and containerized in-vessel compost systems (Engineered Compost Systems, USA)Engineered Compost Systems processing 1 to 200 tons per day ; computer controlled aeration system minimized odor generation Containerized Stationary
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. 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. or ?
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. 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. PT-120 10 foot Pull-type Compost Turner (Midwest Bio-Systems, USA ) WT-3000 Water Trailer (Midwest Bio-Systems, USA) Industrial Windrow composting
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 !