Compost Project

College of Engineering Department of Civil Engineering Composting of Organic Wastes and Production of Organic Fertilizers 2009

Submitted by: Mohammed Khaire Younes Water and Environmental Engineering

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Introduction:

Composting is the transformations of raw organic materials into biologically stable, humic substances suitable for a variety of soils and plant uses. Essentially, composting is controlled decomposition, the natural breakdown process that occurs when organic residue comes in contact with soil. Composting is an ancient technology. There are Roman and biblical references to composting and numerous accounts of farmer composting practices in subsequent millennia. (1) George Washington, the nation’s first president, was also the nation’s first recognized composter. (2,3) Washington was acutely aware of the degradative effects of farming on the soil resource, and he built a "dung repository" to make compost from animal manure so he could replenish the soil’s organic matter. Sir Albert Howard was probably the first agricultural scientist to bring a scientific approach to composting, almost 75 years ago in India. (4) His Indore process involved stacking alternate layers of animal manure, sewage sludge, garbage, straw, and leaves. Stacked material was turned occasionally over 6 months or longer, and leachate from the decomposing residues was recycled to maintain adequate moisture in the piles. Current composting practices use essentially the same principles that Howard promulgated.

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As agriculture became increasingly mechanized after World War II, use of synthetic fertilizers replaced the practice of applying manure or compost to soil to maintain soil fertility, and composting fell into disuse. In recent years there has been resurgence in composting initiatives at various levels as urban and rural areas face increasing landfill costs and decreasing landfill space. In a recently released study of composting trends in the United States, (5) 85% of the nation’s municipal waste stream was identified as organic. (6) This translates to approximately 177 million tons of organic waste per year, mostly as food scraps, yard trimmings, and paper. It does not include organic waste generated from agricultural and industrial sectors, including food processing, paper production, biotechnology, forest products processing, and livestock production. If all of these materials were composted, the estimated potential market demand for finished compost would greatly exceed the amount of compost produced. Markets include agriculture, silviculture (forestry), residential retail, nursery sod and ornamentals production, and landscaping. •

Advantages of aerobic hot composting process:

a) Stabilizes volatile nitrogen. Composted organic matter contains nitrogen in a more stable form (nitrate) that is more usable by plants. b) Kills most pathogens and weed seeds (if piles are above 131°F for 15 days). c) Introduces a wider population of microbes than found in the raw ingredients d) Reduces volume of wastes (by approximately 50%) 3

e) Allows for use of raw materials that shouldn’t be put directly in soil (e.g., sawdust, raw manure) f ) Degrades many contaminants since most pesticides are petroleum- (carbon)-based and thus digestible. Although not a solution to soil contamination, organic matter also has a high capacity to bind heavy metals. g) Guarantees that most of the end product will be humus and slowly decomposing material that will become humus in the soil h) Recycles organic matter on farm and reduces off-farm inputs •

Benefits of compost in the soil

a) Improves soil structure and soil aggregate stability resulting in better drainage, aeration/gas exchange, erosion resistance, workability (tilth). Microbes secrete gluelike compounds that help bind soil particles together. b) Increases moisture retention (100 pounds of humus can hold 195 pounds of water) c) Slow release of nutrients and increased availability of others. Cation Exchange Capacity (CEC) is increased thus increasing availability of Ca, Mg, and K. Also, humic acids help dissolve minerals in the soil, making more minerals available to plants. d) Increases the population and diversity of microbes in soil that continually make nutrients available to plants. Provides food for microbes. e) Helps buffer soil pH. Compost pH is optimally 6.5–7. f ) Promotes disease suppression (different microbes suppress fusarium, pythium, phytopthora, rhizoctonia) g) Plays key role in soil fertility management in organic systems 4

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Potential Disadvantages of composting:

a) Cost and time: Many farmers and gardeners don’t make their own compost because of the labor and expense b) Space needed for composting can take up available production land c) Odor or other impacts on neighbors can create challenges in urban/suburban areas d) Regulations: Regulations on leachate and testing if commercial composter or certified •

Chemistry, Physics, and Biology of Composting:

Since composting is a microbially mediated process, providing the proper environmental conditions for microbes to decompose raw organic materials is crucial for success (Fig 1). The three most important factors for making good compost are the chemical makeup of the raw ingredients or feed stocks (quality and quantity of carbon and minerals, pH), the physical size and shape of the feed stocks and the porosity of the pile, and the population of organisms involved in the composting process (macrofauna and mesofauna; micororganisms including bacteria, actinomycetes, fungi). Compost "happens" either aerobically or anaerobically when organic materials are mixed and piled together. Aerobic composting is the most efficient form of decomposition and produces finished compost in the shortest time.

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Fig 1. Schematic of composting process. Carbon, chemical energy, protein, and water in finished compost are less than that in the raw materials; the finished product has more humus. The volume of the finished compost is approximately 50% less than that of the raw materials. Microbes break down organic compounds to obtain energy to carry on life processes. Under aerobic conditions, the "heat" generated in composting is a by-product of biologic "burning," or aerobic oxidation of organic matter to carbon dioxide. If the proper amounts of food (carbon), water, and air are provided, aerobic organisms will dominate the compost pile and decompose the raw organic materials most efficiently.

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Optimal conditions for rapid, aerobic composting include: 1. carbon-nitrogen (C:N) ratio of combined feed stocks between 25:1 and 35:1

The carbon-to-nitrogen ratio refers to the proportion of carbon to nitrogen by weight in any organic matter. Different types of organic matter have different carbon-to nitrogen or C:N ratios. For example, wood, which is very high in carbon, has a C:N ratio of 500:1 while grass clippings have a C:N ratio of 17:1. C:N ratio of a material can change due to many factors: Plant growth, storage, how fertilized, what an animal was fed. Numbers on a chart are approximations.The optimum C:N ratio for biological activity is between 25:1 and 30:1. Compost piles should ideally start with an overall C:N ratio in this range. Finished compost will be 14:1 to 17:1. Much of the carbon in the pile is released as CO2 as decomposers metabolize organic matter. •

Nitrogenous materials:

Compost materials with low C:N ratios are often called nitrogenous, sometimes “greens”,there is a range of nitrogenous materials as demonstrated on the C:N ratio charts, C:N ratio of a material can change. •

Carbon materials

Compost materials with high C:N ratio are called carbonaceous, sometimes “browns”Carbon materials can be more or less complex as shown on C:N chart (e.g., wood chips), can have C:N ratio of 400:1, straw 70:1, brown leaves 40:1), High carbon materials can be stored easily to use later (e.g., store brown leaves or straw stubble from fall to mix with the abundance of greens in the spring), Carbon materials can be bulkier and thus can provide aeration in a pile

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Factors to consider when estimating C:N ratio of different materials

i. Stage of growth/age of material ii. Storage/treatment iii. Where grown, how fertilized iv. With manures, grain-fed animals will have higher N manure Table: 1 Range of C:N ratio added for some animal manure % C/N

%N

%P

%K

Diary

19

0.5

0.2

0.6

Sheep

nd

1.4

0.5

1.2

Turkey

11

1.5

0.6

nd

Hens

11

1.6

0.5

0.4

Broiler

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4.2

1.7

nd

2. Moisture content:

Low moisture content impedes the composting process, because microbes need water. Low moisture also makes compost piles more susceptible to spontaneous combustion, because moisture content regulates temperature. Moisture content in excess of 60% means pore spaces in the compost pile are filled with water rather than air (oxygen), leading to anaerobic conditions. Feedstocks with different moisture-holding capacities can be blended to achieve ideal moisture content. Carbonaceous materials such as newspaper and wood by-products such as sawdust are often used as bulking (drying) agents.

3. Microorganism:

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The supply of carbon relative to nitrogen (C:N ratio) determines whether net mineralization or immobilization of nitrogen will occur. Mineralization is conversion of organic nitrogen to mineral forms (i.e., ammonium and nitrate); immobilization is incorporation of nitrogen into microbial biomass. As a general rule, if the C:N ratio is greater than 20:1, microbes will immobilize nitrogen into their biomass. If C:N is less than 20:1, nitrogen can be lost to the atmosphere as ammonia gas, causing odor. In general, green materials have lower C:N ratios than woody materials or dead leaves do, and animal wastes are more nitrogen rich than plant wastes are. The complexity of the carbon compounds also affects the rate at which organic wastes are broken down. The ease with which compounds degrade generally follows the order carbohydrates > hemicellulos > cellulose = chitin > lignin. Fruit and vegetable wastes are easily degraded because they contain mostly sugars and starches. In contrast, leaves, stems, nutshells, bark, and tree limbs and branches decompose more slowly because they contain cellulose, hemicellulose, and lignin. 4. Other Environmental Considerations:

A minimum oxygen content of 5% should be maintained for aerobic composting. As microbial activity increases in the compost pile, more oxygen is consumed. If the oxygen supply is not replenished, composting can shift to anaerobic decomposition, which often results in foul odor. Bacterial decomposers prefer pH in the range of 6.0 to 7.5, and fungal decomposers prefer pH of 5.5 to 8.0. Certain materials, such as paper processing wastes and cement kiln dust, can increase pH, and raw animal wastes and processed food wastes can lower pH. If compost pH exceeds 7.5, gaseous loss of ammonia is more likely. The particle size of organic wastes for composting is important for microbial activity and airflow in the compost pile. Smaller particles

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have more surface area per unit volume; therefore, microbes have greater access to their substrate. Thus, grinding of feed stocks before composting can accelerate the composting process. However, if particles are too small, airflow (and oxygen availability) within the compost pile will be restricted, resulting in anaerobic conditions. Ambient air temperature can affect microbes in the compost pile and hence the rate at which the raw materials decompose. In temperate climates, composting is fastest in spring to fall; microbial activity can come to a standstill in winter. The size and configuration of the compost pile affect oxygen content and temperature. For a pile to heat up and stay hot, the minimum volume should be 1 cubic yard. Small piles are able to maintain higher internal oxygen concentrations than large piles can, but large piles retain higher temperature better than small piles do. The ideal pile height for aerobic composting is no greater than 5 to 6 feet.

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The Composting Process:

Mesofauna such as mites, sow bugs, worms, springtails, ants, nematodes, and beetles do most of the initial mechanical breakdown of organic materials into smaller particles. Mesophilic bacteria, fungi, actinomycetes, and protozoa (microbes that function at temperature between 10°C and 45°C (50°F - 113°F) initiate the composting process, and as temperature increases as a result of oxidation of carbon compounds, thermophiles (microorganisms that function at temperature between 45°C and 70°C [113°F - 157°F] ) take over. Temperature in a compost pile typically follows a pattern of rapid increase to 49°C to 60°C (120°F - 140°F) within 24 to 72 hours of pile formation and is maintained for several weeks (Fig 2). This is the active phase of composting, in which easily degradable compounds and oxygen are consumed, pathogens (e.g., Escherichia coli, Staphlococcus aureaus, Bacillus subtilus, Clostridium botulinum) and weed seeds are killed, and phytotoxins (organic compounds toxic to plants) are eliminated. During the thermophilic, active composting phase, oxygen must be replenished by mixing, forced aeration, or turning of the compost pile. 11

Fig 2. Steaming Compost pile during active thermophilic phase of composting, when compost temperature can reach as high as 66 Co As the active composting phase subsides, temperature gradually declines to around 38°C (100°F). Mesophilic organisms recolonize the pile, and the "curing" phase begins. The rate of oxygen consumption declines to where compost can be stockpiled without turning. During curing, organic materilas continue to decompose and are converted to biologically stable humic substances (mature or finished compost). Curing is a critical and often neglected stage of composting. (1) A long curing phase is needed if the compost pile has been managed poorly (too little oxygen, too little or too much moisture) and the compost is unfinished or immature. Immature compost can contain high levels of organic acids and have a high C:N ratio, extreme pH value, or high salt content, all of which can damage or kill plants when the compost is amended to pots or soil. There is no clearly defined duration for curing; common practice in commercial composting operations is to cure for 1 to 4 months, and homeowner compost piles can cure for as long as 6 to 9 months. Compost is considered finished or stable after temperature in the pile core reaches near-ambient levels and oxygen concentration in the middle of the pile remains greater than 5% for several days. These measurements should be made when the compost pile has at least 50% 12

moisture content and a minimum critical volume of 1 cubic yard to retain heat. Dinel et al (7) loosely define compost maturity as the state when compost is dominated by bioresistant organic compounds or humic substances. •

Qualities of Finished Compost

Just as beauty is in the eye of the beholder, the end use market defines compost quality to a large extent. Numerous chemical, physical, and biologic parameters are used to evaluate compost quality. Aside from temperature requirement to kill pathogens (55°C [130°F] for at least 72 hours) and general acceptance of US Environmental Protection Agency biosolids rules (EPA 503) for trace metal concentrations or Jordanian Standards 962/2000,. In general, characteristics such as color, odor, pH, salt content, particle size, presence of undesirable materials (e.g., glass, plastics), heavy metal content, and biologic activity are used to define compost quality for specific end uses (Table 1). It is also important to characterize total and plant-available carbon and nutrients (e.g., nitrogen, phosphorus, potassium, calcium, magnesium, micronutrients) if the compost will be used for crop production.

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Table 2. Compost Quality Guidelines Based on End Use

Characteristic

________________End Use of Compost_________________ Potting Media Top Dressing Potting Grade Amendment Grade* Grade

Soil Amendment Grade* Improvement of agricultural soils, restoration of

Growing medium Formulating growing Recommended without additional Uses blending

Primarily turf top

disturbed soils,

dressing

establishment and

media for potted plants (pH <7.2) maintenance of landscape plants (pH <7.2)

Color

Dark brown to

Dark brown to

Dark brown to

black

black

black

No objectionable

No objectionable

No objectionable

odor

odor

odor

<1/2

<1/4

<1/2

Dark brown to black

Odor

Good, earthy smell

Particle size (in) <1/2

Should be identified Should be

Should be

5.0-7.6

identified

identified

<2.5

<6.0

<5.0

pH

Soluble salt content (mmhos/cm) 14

<20.0

Not more than 1%

Not more than 1%

Not more than 5%

by dry weight of

by dry weight of

by dry weight of

combined glass,

combined glass,

combined glass,

plastic, other

plastic, other

plastic, other

foreign particles

foreign particles

foreign particles

1/8 - 1/2 in

1/8 - 1/2 in

Not more than 1% by dry weight of Foreign Materials

combined glass, plastic, other foreign particles 1/8 - 1/2 in Not to exceed EPA Not to exceed EPA

Not to exceed EPA

Not to exceed EPA standards for

standards for

standards for

unrestricted use

unrestricted use

unrestricted use

(US EPA 503

(US EPA 503

(US EPA 503

Regulations for

Regulations for

Regulations for

Biosolids)

Biosolids)

Biosolids)

<200

<200

<400 EPA

standards for Heavy metals

unrestricted use (US EPA 503 Regulations for Biosolids)

Respiration rate

<200

(mg/kg per hour)# Potential end uses of compost include potting mixes for container crops grown in greenhouses and nurseries, soil amendments for field nursery and sod production, turf and highway greens establishment, landscaping, homeowner gardens, agronomic (i.e., cash grains) and horticulture (e.g., fruits, vegetables) crop production, silviculture (e.g., forestry, paper raw materials), remediation of contaminated sites (e.g., brown fields, mine spoils), and landfill cover. In all cases, compost can replace materials such as peat, topsoil, and synthetic fertilizer. High-value markets (e.g, nurseries, landscaping, turf, horticulture crops) require high-quality compost, whereas low-value markets (e.g., grain crops, site remediation, landfill cover) cannot justify the cost of

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high-quality compost production. The lower value markets can tolerate immature compost if applied several months prior to planting. Potential markets range in size from 0.6 million cubic yards for landfill cover and surface mine reclamation to close to 900 million cubic yards for agricultural and horticultural applications (Table 2). Benefits of compost addition to soil have been noted extensively in recent literature and include increased soil organic matter content, increased water retention in sandy soil, increased cation exchange capacity, restoration of soil structure (i.e., aggregate stability), reduction of fertilizer requirement by at least 50% (8), disease suppression of certain pathogens (9), reduction of heavy metal bioavailability, and bioremediation of xenobiotic-contaminated soils. (10, 11) •

Garden and Kitchen Waste

Landfill banning of municipal organic wastes such as leaves and grass clippings in the late 1980s, along with increased homeowner interest in recycling and organic gardening, has been a boon for home composting. Home composting is one of the most cost-effective organic materials management strategies because it eliminates the costs of collection and processing. (12) There are approximately 1,000 home composting programs in use in the United States, and the number is growing by leaps and bounds. (13) Municipal home composting programs include bin subsidization and distribution, composting workshops, master composter programs (analogous to master gardener), and educational brochures. Homeowners are composting garden and food wastes along with leaves and grass clippings. Numerous composting bins are available for use inside the home (e.g., worm bins or vermicomposters, food scrap composting bins) and in the backyard. Although these bins can differ in construction material (e.g., plastic, wood), 16

configuration, and size, all enable the homeowner to compost organic waste using chemical and biological principles. Organic waste suitable for home composting includes grass clippings, hay, straw, sawdust, wood chips, kitchen waste (e.g., fruit and vegetable peels and rinds, tea bags, coffee grounds, eggshells), leaves, and animal manure (e.g., chicken, cow, horse). It is best to combine dry, high-carbon materials (e.g., woody materials, straw, hay) with wet, high-nitrogen materials (e.g., grass clippings, food scraps, manure) to optimize the C:N ratio, moisture content, particle size, and pile porosity. By following the general guidelines for good aerobic composting, homeowners can minimize foul odor production and vector attraction. Homeowners should not compost meat scraps, fatty food waste, milk products, and bones, because these attract pests to the compost pile or bin. Weed plants can be composted if they have not gone to seed. It is best not to compost treated-wood waste, pet waste, and diseased plants, because their toxic substances and pathogens may not be destroyed in the composting process. Under most home composting conditions, it is difficult to achieve the high temperatures required to kill pathogens and weed seeds. As home composting has become more prevalent, numerous sources of information have become available.

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Large-Scale Composting of Industrial and Agricultural Wastes

Fig 3. Common feed stocks in large-scale commercial composting include food processing wastes such as (A) cull potato and (B) dairy cow waste and straw bedding mixed with sawdust. Commercially available compost is derived from a variety of organic by-products, including animal manure, food processing waste, biosolids (sewage sludge), yard debris, and wood processing byproducts (Fig 3). These materials are generated in large volume and are composted by either the waste generator or a commercial composter. In either case, states regulate large-scale composting; most facilities must obtain composting permits to ensure minimal negative environmental impact. As with home composting, commercial composting must respect the same set of biophysical conditions for proper aerobic composting. Because large volumes of organic wastes are involved, management of compost piles is intensive. In most cases, raw materials are either piled in long windrows outside or placed in long beds in climate-controlled buildings. Compost piles must be aerated either passively or actively (Fig 4). The most prevalent composting techniques used by large-scale composters are forced-air static piles, passively aerated static piles, and turned windrows (using either tractorpulled or self-propelled windrow turning machines.) Some large-scale composting operations use completely enclosed in-vessel equipment to achieve maximum control of temperature, oxygen, and moisture.

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Fig 4. Techniques for large-scale composting include (A) mixing poultry litter and agriculture by-products in a feed mixer for passive aeration composting, (B) using a tractor-pulled windrow turner to mix cannery wastes with sawdust and municipal leaves, and (C) turning poultry litter using a self-propelled windrow turner

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The current Jordanian compost situation and animal manure market:

Livestock growers are cleaning the habitat surfaces with a changing frequency according to the type of animals raised. The manure is cleared from the cowsheds and the chicken houses and transferred to a storage area in the farm or near it. The size of the storage area depends on the number of livestock raised. As the demand for organic materials is higher than the supply, the manure is sold to traders. Depending on the size of the farm, loading the manure from the storage areas is conducted manually or with the help of a tractor. The traders pay the farm owners for the manure. The price for poultry manure is higher (68 JD per M³) than that of cattle manure (3-4 JD per M³) (these prices are according to the case study provided by the ministry of agriculture) and these prices are for the manure in the field without the loading and transportation cost which they may reach from 150% to300% of the manure price. Many other factors are controlling the manure prices; from these factors is the season. The demand for manure is periodic in high season the demands in the maximum phase therefore the manure will reach the maximum price, while in winter (the low season for manure) the price will be too low. In low season the farmers are storing the manure in storage and these quantities in storage which will be called the buffers quantities. The prices are also depending on the scale of the production where high scale producers are selling the manure with lower price than the low scale producers, where the loading and transportation cost will be much lower. The farmers buy the manure from the traders paying 7-8 JD per M³ of cattle manure and about 10-12 per M³ of poultry manure which is about the double prices of what the traders are paying. Based on the price of the treated manure in Jordan the treated animal waste can be estimated delivered to the farmer

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between 20-25 JD but this treated manure is not treated in a scientific method its just a mixing of untreated manure with different ratios.

Livestock Growers

Inhabitants

Traders

Environment

Agricultural

Farms The presentation of the data shows that all the participants included in this particular branch are satisfied (traders and farmers). The livestock growers receive a high value for their manure, an additional income is achieved. The customers of the fresh manure pay a low price for untreated manure. There is no awareness of the use of compost carrying out a program for the treatment of manure necessitates a publicity campaign explaining the advantages of the use of compost. The only factor that suffers in the present system is the

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environment. The use of untreated manure causes an environmental hazard and damages the quality of life in the agricultural areas, where the manure is stored and used. As in the present situation the damage is only environmental and the inhabitants, the solution of the problem necessitate the involvement of the State. The livestock growers will continue to receive the present value for the manure, the traders will market the product buying the compost from the treatment sites and supplying it to the users. Beside the using Manure direct from the Traders, there are 6 factories that are doing compost from animal manures; the production potential per year is estimated to be about 40,000 ton per year (about 120,000 m3). Actually none of them used advance Technology to assure that the specification for compost are done (see Table 3). Table 3: agricultural area (dunam) and market potential (cubic meter) in Jordan Valley. Type of plant

Area in dunams

Vegetables in

Amount of manure per dunams in m3

Market Potential (m3)

13,854

3

41,562

Vegetables in open area

180,577

2

361,154

Orchards

97,026

1

97,026

Total

291,457

greenhouses

22

499,742

Table 4: of organic fertilizer factories, the production potential and their location in Jordan Name of the factory

Production potential

Location

The international establishment for fertilizers technology

tons/day 30

The Jordanian- agricultural company for organic fertilizers production

tons/day 80

Duleil

The Jordanian international industrial company

tons/day 60

Alhalabat palace

Doghmosh establishment for agriculture and trade businesses

tons or 400-500 upon request

Tneeb

Khaled Al-Darabani company

ton/ year 5,000

Alkastal

Der Alla factory

ton per 20,000 year

Der Alla

None of these manufacturers is using the advanced technology or following the standard quality for composting the manure, and due to no authorities controlling and supervision, the current situation is good in some points but in the other hand it has many disadvantages need to be controlled. No improvement in the current situation will be achieved without the authorities help. From this situation we became with the idea of compost production according to the standard quality and to lay out Jordanian quality for compost production, in cooperation with the ministry of environment, ministry of agriculture and the German supporter.

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Conclusion

Composting of organic wastes is an environmentally sound means of diverting organic waste from landfills and producing valuable soil amendments. Composting is a microbially mediated process that requires a specific set of chemical and physical conditions. Compost can be produced on a variety of levels ranging from home composting to large commercial operations. Compost can be used in agriculture, horticulture, and silviculture production, as well as landscaping, home gardens, and remediation of contaminated sites. States and municipalities could adopt goals for reducing or eliminating organic waste land filling so that composting becomes more widespread and more economically viable. In addition, the United States could develop federal guidelines for compost quality standards to maximize beneficial use of finished compost.

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References 1. Rynk R. On-Farm Composting Handbook, NRAES-54. Ithaca, NY: Natural Resource, Agriculture, and Engineering Service, Cooperative Extension; 1992:1-186. 2. Arner R. George Washington: the composter of our country. Washington Post. Sunday "Free for All," September 10, 1995:A-20. 3. Pogue DJ, Arner R. George Washington, the revolutionary farmer: American’s first composter. City Farmer Web site, Canada’s Office of Urban Agriculture, February 13, 1997;1-3. Available at: www.cityfarmer.org (accessed May 1999). 4. Howard A. An Agricultural Testament. London, England: Oxford University Press: 1943:39-52. 5. US Environmental Protection Agency. Organic Materials Management Strategies. EPA530-R-97-003. Washington, DC: US Government Printing Office; 1998:1-53. 6. Sparks K. Organics take a number. Resource Recylcing. 1998;17:32-35. 7. Dinel H, Schnitzer M, Dumonet S. Compost maturity: chemical characteristics of extractable lipds. Comp Sci Util. 1996;4:16-25.

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8. Werner W, Scherer H, Olfs HW. Influence of long-term application of sewage sludge and compost from garbage with sewage sludge on soil fertility criteria. Z Acker Planzenblau. 1988;160:173-180. 9. Hoitink HAJ, Stone AG, Han DY. Suppression of plant diseases by composts. Hortscience. 1997;32:184-187. 10. Barker AV. Composition and uses of compost. In Rechcigl JE, McKinnon HC, eds. Agricultural Uses of By-Products and Wastes. ACS Symposium Series 668. Washington, DC:1997;140-162. 11. Al jaar ,Mustafa Feasibility study about production and Demands for Manure in Jordan

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