Environmental Microbiology

Composting – Methods, Types, Factors, Importance

What is Composting? Compost is a mixture of organic materials used as a plant fertiliser and to improve the physical, chemical, and...

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This article writter by MN Editors on October 12, 2022

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Composting - Methods, Types, Factors, Importance
Composting - Methods, Types, Factors, Importance

Contents

What is Composting?

  • Compost is a mixture of organic materials used as a plant fertiliser and to improve the physical, chemical, and biological qualities of soil. It is typically produced by decomposing plant matter, food scraps, recycling organic materials, and composting manure.
  • Rich in plant nutrients and helpful organisms such as bacteria, protozoa, nematodes, and fungi, the resulting mixture is ideal for plant growth.
  • Compost enhances soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, hence decreasing reliance on commercial chemical fertilisers.
  • Compost provides nutrients as fertiliser for crops, acts as a soil conditioner, increases the humus or humic acid content of the soil, and introduces beneficial bacteria that suppress pathogens in the soil and minimise soil-borne diseases.
  • At its most basic, composting involves a mixture of “greens” (green trash) and “browns” (brown waste).
  • Greens are nitrogen-rich materials like leaves, grass, and food wastes. Browns are carbon-rich woody materials such as stalks, paper, and wood chips. The materials decompose into humus over the course of several months.
  • Composting can be a multi-step, tightly monitored process with measured water, air, carbon- and nitrogen-rich material inputs.
  • The decomposition process is facilitated by shredding plant materials, adding water, and providing adequate aeration by regularly turning the mixture in an open pile or “windrow” procedure.
  • Fungi, earthworms, and other detritivores decompose organic matter further.
  • Aerobic bacteria and fungi control the chemical reaction by turning the inputs into heat, carbon dioxide, and ammonium.
  • Food and other compostable materials make up around 20% of waste in landfills, and these products take longer to biodegrade in the dump. Therefore, composting is an integral aspect of waste management.
  • Composting is an environmentally superior option to putting organic waste in landfills because it minimises methane emissions from anaerobic decomposition and delivers economic and environmental co-benefits.
  • Compost can also be used for land and stream reclamation, wetland building, and landfill cover, among other applications.
  • Certain proportions of these substances will allow microorganisms to function at a rate that will cause the compost pile to heat up.
  • Active management of the pile (e.g., stirring the compost heap with a pitchfork) is required to maintain the proper levels of oxygen and moisture.
  • Maintaining high temperatures of 130–160 °F (54–71 °C) until the materials are broken down is dependent on the air/water balance.
  • The optimal carbon-to-nitrogen ratio for composting is about 25:1. Hot composting focuses on maintaining heat to accelerate decomposition, resulting in faster production of compost.
  • Carbon-to-nitrogen ratios of 30 carbon units or less are optimal for rapid composting. Above 30, the substrate becomes nitrogen-deficient. Below 15, it is likely to emit ammonia instead of nitrogen.
  • Almost all plant and animal remains include carbon and nitrogen in varying proportions. Depending on the species, the typical ratio of fresh grass clippings to dry fall leaves is around 15:1 and 50:1, respectively.
  • Composting is a continuing and dynamic process that requires constant addition of new carbon and nitrogen sources and active control.

Important ingredients required for function of Microorganisms

  • Carbon is required for energy; the microbial oxidation of carbon generates the necessary heat for later composting steps. High carbon content materials are typically dark and dry.
  • Nitrogen is required for the growth and reproduction of more organisms to oxidise carbon. High nitrogen materials tend to be green and moist. They may also contain vibrant fruits and veggies.
  • Oxygen is essential for oxidising carbon, the process of breakdown. Aerobic bacteria require oxygen concentrations greater than 5% to execute the actions required for composting.
  • The correct amount of water is required to maintain activity without generating anaerobic conditions.

Mechanism of Composting

Organisms can decompose organic materials in compost if the proper mixture of water, oxygen, carbon, and nitrogen is present. There are two basic groups of decomposers: chemical decomposers, which execute chemical processes on organic waste, and physical decomposers, which reduce trash to smaller bits by grinding, tearing, chewing, and digesting.

Chemical decomposers

Bacteria 

The most abundant and significant microorganisms in compost are bacteria. Bacteria convert carbon and nitrogen into plant-available nutrients, including nitrogen, phosphorus, and magnesium. Depending on the composting phase, mesophilic or thermophilic bacteria may predominate.

  • Mesophilic: Mesophilic bacteria convert organic matter into thermophilic compost through oxidation. The subsequent curing process makes the new compost more bioavailable to plants.
  • Thermophilic: Thermophilic bacteria do not reproduce and are inactive between 5 and 25 degrees Celsius (23 and 77 degrees Fahrenheit), nevertheless they are widespread in soil. Once the mesophilic bacteria have begun to degrade organic materials and raise the temperature to the appropriate range, they become active. It has been demonstrated that they penetrate soils via rainwater. They are extremely widespread due to numerous characteristics, including the resilience of their spores. In common mixtures, thermophilic bacteria survive at temperatures of 40–60 °C (104–140 °F). Large-scale composting methods, such as windrow composting, may exceed this temperature, hence potentially destroying beneficial soil microbes and pasteurising the waste.
  • Actinomycetota: Actinomycetota are required to breakdown paper products such as newspaper, bark, etc., as well as other difficult-to-decompose big molecules such as lignin and cellulose. Actinomycetota is credited with the “pleasant, earthy aroma of compost.” They make carbon, ammonia, and nitrogen available to plants as nutrients.

Fungi 

  • Mold and yeast help break down things that bacteria cannot, such as cellulose and lignin in wood.

Protozoa 

  • In addition to contributing to the biodegradation of organic waste, protozoa consume inactive bacteria, fungi, and microorganisms.

Physical decomposers

  • Ants – construct nests, making the soil more permeable and delivering nutrients to various regions of the compost.
  • Beetles – The larvae of beetles feed on rotting vegetables.
  • Earthworms – Earthworms absorb partially decomposed organic matter and excrete worm castings, making nitrogen, calcium, phosphorus, and magnesium accessible to plants. In addition to increasing aeration and drainage, the tunnels they build as they go through the compost improve the compost’s aeration.
  • Flies — consume nearly all organic matter and contribute bacteria to the compost. Mites and thermophilic conditions that are inappropriate for fly larvae control their population.
  • Millipedes — decompose plant matter.
  • Rotifers — consume plant matter.
  • Snails and slugs – feed on fresh or living plant matter As they can harm plants and crops, they should be removed from compost prior to use.
  • Sow bugs — feed on decaying wood and plant matter.
  • Springtails – Feed on mushrooms, mould, and rotting plants.

Phases of composting

Under optimal conditions, composting progresses through three significant phases:

  • Mesophilic phase: an initial mesophilic phase in which mesophilic bacteria perform degradation at moderate temperatures.
  • Thermophilic phase: as the temperature rises, a second thermophilic phase begins in which diverse thermophilic bacteria carry out breakdown at higher temperatures (50 to 60 °C; 122 to 140 °F).
  • Maturation phase: as the supply of high-energy molecules dwindles, the temperature begins to fall, and mesophilic bacteria resume their predominance.

Compost Ingredients

  • To survive, organisms that breakdown organic waste require nitrogen, carbon, air, and water.
  • Since all biodegradable materials include carbon and various amounts of nitrogen, it is only necessary to use the proper combination of materials to establish the optimal carbon-to-nitrogen ratio and to maintain the proper air and water levels to obtain optimal outcomes.
  • The optimal ratio of carbon to nitrogen in a compost pile is 25 to 30 parts carbon to 1 component nitrogen. If your pile contains an excessive amount of carbon-rich materials, it will become drier and take longer to decompose.
  • An excess of nitrogen-rich materials might result in a compost pile that is slimy, moist, and smelly. As needed, carbon-rich or nitrogen-rich material can be added to remedy these issues.

“Greens” for Nitrogen

  • Nitrogen is one of the fundamental building components of life and is required for plant and animal growth and reproduction.
  • The ratio of nitrogen to carbon is often higher in fresh organic material (often referred to as greens). The presence of many greens in a compost pile ensures that decomposers can develop and reproduce rapidly.
  • Fresh grass clippings, food scraps, and coffee grounds are examples of greens that can be added to a home compost pile.

“Browns” for Carbon

  • Carbon, which is present in larger concentrations in brown plant matter, is a chemical that is vital to all forms of life.
  • Carbon serves as a food source for decomposers, keeping them alive while they decompose organic matter.
  • Included among the brown materials that can be added to a compost pile are dead leaves, branches, twigs, and paper.
  • A rule of thumb for achieving the optimal carbon-to-nitrogen ratio in your home compost is to add two to four parts brown materials for each part green materials.

Oxygen and Water

  • Decomposers, like all other living organisms, require oxygen and water to exist. To expedite the composting process at home, you must ensure that your composting system has sufficient air and water.
  • As stated previously, if you are not in a hurry to produce finished compost, you do not need to maintain your trash; decomposition will still occur, albeit at a considerably slower rate.
  • Optimal air movement can be obtained by layering materials, ensuring materials are tiny (preferably no thicker than a finger), and constantly turning piles (or adding another type of aeration system).
  • As for moisture, the ideal residential compost pile will be about as wet as a sponge that has been squeezed dry. If you include food waste in your pile, it will likely be sufficiently moist; if not, simply add water.

Factors Affecting The Composting Process

Certain environmental conditions significantly affect the rate of decomposition. Composting organisms require food (carbon and nitrogen), air, and water. When given the proper conditions, they will generate compost rapidly. In addition to surface area/particle size, volume and temperature can affect the rate of decomposition by organisms.

Food Factor

  • Carbon and nitrogen supply food for organisms in the form of organic matter. As previously mentioned, bacteria use carbon as a source of energy and protein for growth and reproduction. Carbon and nitrogen amounts vary among organic substances.
  • Carbon-rich substances are typically brown and dry, such as leaves, straw, and wood chips. Materials containing nitrogen are typically wet and green, such as new grass clippings and food waste.
  • Remember that fresh, juicy materials are typically higher in nitrogen and will disintegrate more rapidly than older, drier, and woodier tissues that are higher in carbon.
  • The optimal combination for fast breakdown is a C:N ratio ranging between 25:1 and 30:1. If the ratio of oxygen to carbon exceeds 30:1, heat production decreases and decomposition is slowed. You may have observed that a mound of leaves or wood chips can remain undisturbed for a year or more.
  • When there is an excess of nitrogen, your pile will likely emit odorous ammonia gas. Additionally, excessive nitrogen can induce an increase in pH, which is harmful to certain microbes.
  • The C:N ratio is not required to be precise. The values in Table 1 are computed based on dry weight. Without knowing the moisture content of the employed materials, it is difficult to obtain an exact C:N ratio.
  • The art of composting includes blending ingredients to obtain an optimal C:N ratio. A basic rule of thumb is to formulate a volume-based recipe with between one-fourth and one-half high-nitrogen ingredients.

Composting Methods

AirCompost needs to be aerated or it creates an anaerobic environment for bacteria which produces unpleasant odours and attracts verminWaterEssential to keep the compost moistVegetable MatterEssential to obtain organically rich compostWormsDigest decomposed matter and release worm castings that provide plants with the nutrients they need for growthCarbon-nitrogen mix (brown and green waste)Essential to create the right temperature for creating compost from green waste and to kill seeds and diseaseBacteria (EMO’s)Will decompose the food before the worms eat itSoldier FliesNot essential but devours waste food quicker than worms or bacteriaOther Beneficial BugsCockroaches and other insects that help in the decomposition process (including maggots if putting meat in a compost pile – not recommended for most composters except the Compot.
Elements Generally Required In Most Systems In Order To Produce Compost.

1. Open Air Composting

  • Organic yard debris like grass clippings, leaves, twigs, etc. can be composted utilising the open-air approach.
  • They are brought, sifted to remove any unwanted items, and then shredded.
  • Once finished, the shredded waste is stacked in neat rows outside. Naturally occurring microorganisms then devour them, releasing heat and steam through the windows.
  • Regular turning of the rows is necessary to provide sufficient oxygen for the microorganisms to thrive.

Advantages of Open Air Composting

  • Farmers that have a lot of green waste to mulch with animal manure can benefit greatly from open air composting.
  • Chickens benefit greatly from outdoor piles for the purpose of foraging and catching food.
  • If you have the time, an outdoor composting system is ideal.
  • The price tag is more reasonable.

Disadvantages of Open Air Composting

  • Worms are attracted to open-air composting, although some may leave if the conditions are unfavourable.
  • Similarly to how pH is essential, temperature is also a crucial element. If the necessary temperature is not attained, it will not disintegrate and may become a huge mess.
  • Due to the mild temperatures, both snakes and rats are able to nest and reproduce in these systems. It must be turned frequently for aeration.
  • Large quantities of green waste are required to produce a little amount of compost. If they are packed with the incorrect materials, they may emit an objectionable stench. The same phenomenon occurs when there is no compost turning. 
  • Composting in the open air necessitates a large amount of garden space and demands the dispersal of materials around the garden.
composting
composting

2. Direct Composting

  • Direct Composting involves digging a pit or trench and burying food leftovers.
  • It is likely the oldest and most effective way of composting, but like all other systems, it has limitations.
  • The primary disadvantage is that it takes a long time to disintegrate unless everything is chopped apart.

Process

  1. Create a hole around 12 inches (30 centimetres) deep and place your kitchen scraps within.
  2. Mix in at least as much brown debris (shredded leaves, paper, ashes, nut shells, used potting soil) and cover the top of the hole with soil that has been removed.
  3. As with any sort of composting, avoid composting meats, peanut butter, dairy, fatty meals, sick plants, carnivore faeces, charcoal fire ashes, and glossy paper.
  4. In as little as a month, your subterranean stew should transform into nutrient-rich compost that can be used to feed neighbouring plants or enrich a future garden bed.
  5. Make the hole in an empty area of the garden where you have no plans to plant this year. 
  6. Alternately, dig composting trenches between your vegetable or flower rows. The following year, plant where the compost has developed, and compost where the plants grew the year before. In big garden plots, a three-year crop rotation, compost trench, and path can be established.

Advantages of direct composting

  • There is no need to turn the compost. Once the leftovers and brown material have been buried, your work is complete.
  • Also, there is no need to transport the completed compost. Wherever it is buried is where it will enrich the soil.
  • At this deep root level, plants benefit from receiving their dose of compost nutrients.
  • Direct composting eliminates the risk of unpleasant odours and unattractive mounds.

Disadvantages of direct composting

  • Animals, including the family dog, the local raccoon, and a hungry bear, may dig into your compost and destroy your garden as a result (this can be a problem with compost piles and bins too). The remedy is the same as it is for any of the larger garden pests: ensure that your beds are protected by sturdy, high, and tight fences.
  • With direct composting, the compost is produced on-site. In most circumstances, it is impractical to dig it up and use it elsewhere in the garden.

3. Tumbler Composting

  • Tumbler Composting is available commercially or as a do-it-yourself project in a variety of sizes and configurations ranging from single to double units.
  • This is an excellent system provided you are somewhat strong and willing to turn it daily or every few days.
  • Others find it difficult, especially as they advance in age. However, you can obtain motorised ones that facilitate turning.
  • You often need two of these systems so that you may let one rest for a few months before emptying it. While this is occurring, you fill the second container.
  • If you have a considerable amount of green and brown waste to dispose of and the space to accommodate this system, it may be an excellent option. However, similar to the bay system, a small amount of soil requires a substantial volume of garbage.
  • If you’re only adding green and brown garbage, a bay system would suffice, but you’ll need to keep an eye out for snakes and rats nesting in the warm compost due to a lack of space.

Pros And Cons Of Tumbler Composting

  • Worms are frequently added, which may be ineffective because they will die if the temperature rises.
  • The correct mixture is essential, as the tumbler can become a foul-smelling slushy mess or a solid mass.
  • While the first one decomposes, the second one is being filled.
  • Equally unfavourable are excessive and insufficient degrees of rotation.
  • Only particular foods can be introduced, and decomposition takes a lengthy period.
  • It takes a huge amount of green garbage to produce a tiny amount of compost. It involves constant, laborious labour that some individuals find too difficult.
  • However, it is terrific workout for some individuals.
  • It is noticeable and occupies yard space, particularly if you have two.
  • Inconsistent turning may lead the contents to clump into a large mass, making it extremely difficult to turn and empty.
  • Unless insulated, they will only function in the summer.
  • If infested with Soldier flies, it might be unpleasant for some individuals to open the door and be met with a swarm of flies. Identical to a worm farm
  • The Soldier Flies may make the air stink.
  • Depending on the size, this is a great option for your green garbage, but it may be too little.
  • Green waste must be shredded in order to fit certain containers and to decay more rapidly.
  • If you do not turn them, the acid produced by food waste can corrode the bottom of metal containers. A frequent occurrence when people fail to turn them off
  • They have been known to emit foul odours depending on the contents.
  • Similar to an open-air system, you would need to monitor the heat produced inside.
  • Small containers can be purchased instead of large containers, so conserving room. Double containers can be obtained so that you can alternate between filling and resting one.
  • After a few months of resting, it produces wonderful compost.
  • You cannot dispose of ALL kitchen waste with these systems. Only fruit, vegetables, and paper or cardboard
  • If you do none of these things and simply put your garbage in and allow it to sit and degrade, it will function, but it will be difficult and time-consuming to finally turn and empty.
  • Similar to the open-air method, you need two to three bins, depending on the amount of waste, for them to function effectively.
composting Methods
composting Methods

4. Worm Farm Composting

  • For many, Worm Farm Composting is the most popular and favoured method of composting due to its capacity to cultivate worms, produce compost and compost tea, and keep rodents out of the compost.
  • Worms create castings that are rich in nutrients but contain less nitrogen than other composting methods.
  • Worm farms can be used even if there is no garden available.
  • Copper, which is poisonous to your worms, leaches from metal containers.
  • Using plastic containers to collect the juice necessitates the addition of a drain or a method for rotating the containers to collect the worm tea.
  • They must be maintained out of the sun, frost, and rain, and in a location that is neither too hot nor too cold.
  • Worms are temperamental creatures that will attempt to leave their containers if they are unhappy with their environment.
  • It is recommended to utilise local worms in your region.

Pros And Cons Of Worm Farm Composting

  • It is necessary to introduce worms and give bedding to preserve the worms.
  • If conditions are not optimal, worms perish from overheating or freezing.
  • Produces exquisite juice, which must be collected lest worms drown.
  • They do generate lovely worm tea and compost, however.
  • No onions, meat, oil, dairy products, eggs, or citrus may be added.
  • Preferably, the worms should not be overfed.
  • Decomposition requires time; worms only consume degraded food.
  • For faster breakdown, it is beneficial to cut the food into small pieces, which requires a little extra effort.
  • As there are no heated zones, weed seeds and tubers are not killed.
  • Soldier Fly larvae can enter your worm farm and either kill the worms or crowd them out, leaving you with no worms. During the winter, when soldiers hibernate (depending on the climate), there is nothing to breakdown their excrement if it is too cold.
  • When trays are full, it can be difficult to rotate and empty them.
  • Worms will perish if not fed, as they are unable to roam around a garden in search of food.
  • If you go for the holidays, you must arrange for someone to feed your pets.
  • It is visible and occupies a minimal amount of space in your garden.
  • Suitable for a garage in a modest townhouse without a backyard.
  • Worm farming is a rewarding and efficient approach for producing worms and compost, according to many.

5. Emo Composting

  • EMO Composting, also known as Effective Microorganisms, is a system typically used for indoor composting, but it can be utilised by anyone who prefers this way of composting or who is in an apartment.
  • Bokashi is the most popular product that uses EMOs, although other indoor systems can also use it, and some systems also use a carbon filter in the lid to filter odours.
  • Typically, you need two of them so that one can rest while the other is filled.
  • You can collect juice to utilise in your garden.
  • But you cannot use the Bokashi System for everything in your kitchen.
  • Numerous online retailers offering the Bokashi System sell EMO.
  • If you so choose, you can employ EMOs in other systems to enhance the composting process.

Pros and Cons of EMO Composting

  • It requires Efficient Microorganisms (EMOs for fermentation / breakdown)
  • This necessitates collection, but is beneficial for your plants.
  • Oil, water, milk, juice, and bones should not be added, although the business has stated that they may be included.
  • Once it is full, it must sit until all of the material has decomposed. Therefore…
  • While the first one decomposes, you must fill the second one. This may be an issue in a unit, however it depends on the available space.
  • When waste is initially buried, it is acidic and cannot be placed near plants since it could harm their roots.
  • It takes seven to ten days for the garbage in the garden to neutralise. This is not an issue if the waste is buried in an acceptable location.
  • You must keep the lid covered during decomposition to avoid attracting insects.
  • If it is improperly closed, it can present a problem with insects inside the home.
  • Bacteria alone are used to decompose garbage, thus the process is not incredibly quick.
  • It occupies space in your kitchen, shed, or balcony. It requires a new hole to be dug every time it is emptied, which isn’t a problem provided you have enough room.
composting Methods
composting Methods

6. Combination Composting

  • Combination Composting, also known as Compot Composting, combines open-air composting, direct composting, vermicomposting, and EMO composting.
  • All components of composting are utilised, and the method is suitable for the majority of residential situations.
  • For certain individuals, it too presents obstacles. For me, though, the obstacles are fewer and the rewards are greater.
  • All of your kitchen waste can be composted, not just portion.
  • Consequently, you have over fifty percent less rubbish to place in your council bin each week.
  • It is quicker and less labor-intensive than most other composters.
  • And it enriches the soil with all of your household garbage.

Pros and Cons of Compot Composting

  • Throw away all kitchen trash, including meat, dairy, citrus, eggs, onions, oil, coffee, and tea bags.
  • It will compost all biodegradable materials.
  • Perfect for animal waste — puppy doos etc. – gone in 20 minutes (not in your veggie garden)
  • Decomposes incredibly rapidly – with the aid of the Black Soldier Fly
  • There will be worms. You should not add worms unless your soil is extremely poor.
  • Your worms won’t perish. They take care of themselves, so you may enrich your garden without exerting any effort. You do not need to feed your worms while you are on vacation.
  • By planting a few around your garden, it will provide nourishment to all of the different areas.

7. Commercial Composting

  • Commercial composting differs from home composting and utilises distinct ingredients.
  • Compost is produced in long rows utilising materials such as sawdust, pine bark, sand, ferrous sulphate, and sometimes some ammonium sulphate.
  • It is typically bagged after six weeks and is turned every three to four days.
  • The nutritious value of inexpensive commercial compost is minimal.
  • There are, however, little independent commercial compost companies that produce a product of higher quality than the huge commercial compost companies. However, they are more pricey.
  • The adage “you get what you pay for” holds true with commercial compost.
  • The less expensive commercial compost is an excellent filler for raised garden beds or for backfilling a Compot in sandy or clay soil.
  • Or it can be used with composted soil to fill raised garden beds or possibly a potted plant.
  • If you are using commercial compost to grow plants, you should use a high-quality propagation mix.

Pros and Cons of Commercial Composting

  • Different manufacturers employ different ingredients, thus some may be good while others are not and are frequently not sufficiently decomposed before use.
  • If you require big quantities, commercial compost is ideal for filling a new garden bed or a raised garden bed because it is often inexpensive and consistent between brands.
  • It varies by brand, so you must experiment with various brands to discover one you like, as it may not be quality compost.
  • Depending on the quality of the ingredients and the manufacturer, the price can vary.
  • Typically, small independent producers generate more expensive, superior compost.
  • In the end, nothing beats generating your own compost. You are aware of what goes in and what comes out. No additional chemicals or fertiliser. Consequently, if you cultivate your own vegetables, you are aware of what goes into the soil. It is difficult to tell exactly what is in your food if you purchase it commercially unless you get certified organic compost.
composting Methods
composting Methods

8. Mechanical Composting

  • Mechanical Composting is an effective method of composting that employs electricity to generate the necessary heat and rotation of the contents to produce semi-composted trash in less than 24 hours.
  • This system is ideal for restaurants, hotels, motels, hospitals, schools, and kindergartens, as well as any other major institution that generates large amounts of garbage from several individuals.
  • It is a manageable in-house system as opposed to sending waste to municipal dumps. However, you must further compost the trash, thus you need someone to collect the remaining contents for further composting in a garden bed or bay composting system.
  • There are also small systems that may be suitable for private residences, but they can be rather costly and will, of course, incur continuing electrical costs. Like all composters, they have advantages and disadvantages, but they generate semi-composted soil rapidly.

Pros and Cons of Mechanical Composting

  • They are quick and effective.
  • Produce a great deal of heat.
  • Create an earthy aroma.
  • Require a well-ventilated outdoor space or a space with an exhaust fan.
  • Depending on the size necessary, occupy a great deal of room.
  • Are expensive to acquire and maintain.
  • They demand electricity, resulting in extra costs.
  • Regularly remove and store compostable waste for pickup.
  • Therefore, additional storage space is required.
  • This trash is not entirely digested and hence requires more composting.
  • Someone must still collect the rubbish to further compost it.
  • Produces semi-composted soil that smells like composted soil within 48 hours.
  • Excellent option for schools, kindergartens, restaurants, hotels, and motels, among others.

Factors affecting aerobic composting

1. Aeration

  • Composting requires a great deal of oxygen, especially during the first phase. O is derived from oxygen, making aeration essential for aerobic composting. Where there is insufficient oxygen, the growth of aerobic microorganisms is restricted, resulting in a slower rate of decomposition.
  • In addition, aeration eliminates surplus heat, water vapour, and other gases trapped in the pile. In hotter areas, where the risk of overheating and fire is greater, heat removal is especially crucial.
  • Therefore, adequate aeration is essential for effective composting. It can be attained by managing the physical quality of the materials (particle size and moisture content), the pile size and ventilation, and by assuring adequate turning frequency.

2. Moisture

  • The metabolic activity of microorganisms requires the presence of water. Materials for composting should retain a moisture content between 40 and 65 percent.
  • Composting proceeds more slowly when the pile is too dry, and anaerobic conditions are created when the moisture content exceeds 65 percent.
  • In practise, it is recommended to begin the pile with a moisture content of 50 to 60 percent and end with a moisture content of 30 percent.

3. Nutrients

  • As primary nutrients, carbon (C), nitrogen (N), phosphorous (P), and potassium (K) are required by microorganisms. The C:N ratio of raw materials is especially significant.
  • However, ratios between 20:1 and 40:1 are equally acceptable. Where the ratio exceeds 40:1, the growth of microorganisms is restricted, leading to a longer composting time.
  • A C:N ratio of less than 20:1 results in the underutilization of nitrogen, with the excess being lost to the atmosphere as ammonia or nitrous oxide, which can cause odour issues. The final product should have a C:N ratio between 10:1 and 15:1.

4. Temperature

  • There are two temperature ranges involved in the composting process: mesophilic and thermophilic.
  • At later phases of composting, when thermophilic organisms take over, the optimal temperature range may be between 50 and 70 degrees Celsius.
  • Aerobic composting is characterised by high temperatures, which indicate active microbial activity.
  • Pathogens are often eliminated at temperatures of 55 °C or above, whereas the threshold temperature for eliminating weed seeds is 62 °C. Temperature can be controlled by turning and aeration.

5. Lignin content

  • Lignin is one of the primary components of plant cell walls, and its intricate chemical structure renders it extremely resistant to microbial destruction (Richard, 1996). This characteristic of lignin has two repercussions.
  • One is that lignin affects the bioavailability of the other cell-wall elements, resulting in a lower real C:N ratio (ratio of biodegradable C to N) than is typically reported. The second is that lignin acts as a porosity enhancer, which provides conditions that are favourable for aerobic composting.
  • Consequently, while the addition of lignin-decomposing fungus may in some situations enhance accessible C, expedite composting, and reduce N loss, in others it may result in a greater real C:N ratio and poor porosity, both of which lengthen the composting period.

6. Polyphenols

  • Tannins that are hydrolyzable and condensed are polyphenols (Schorth, 2003). Tannins that are insoluble and condensed bind cell walls and proteins, making them physically or chemically inaccessible to decomposers.
  • Tannins that are soluble, condensed, and hydrolyzable react with proteins to inhibit their microbial breakdown and consequently N release.
  • As inhibitory factors, polyphenols and lignin are getting more attention. Palm et al. (2001) advise using the content of these two compounds to classify organic wastes for more efficient on-farm exploitation of natural resources, including composting.

7. pH value

  • Although the natural buffering effect of the composting process allows for a wide range of acceptable pH levels, the pH should not exceed eight.
  • At higher pH values, greater quantities of ammonia gas are produced and may be lost to the atmosphere.

8. Techniques for effective aerobic composting

  • Simple replication of composting techniques does not always provide prospective composters with the correct answer. This is due to the fact that composting occurs in a variety of locales and climatic conditions, utilising different materials with distinct physical, chemical, and biological qualities.
  • A comprehension of the principles and technological alternatives, as well as their suitable application, may be beneficial in supplying the compost pile with the optimal environment.

9. Improved aeration

  • To create a uniformly high-quality final product, the entire pile must receive a enough amount of oxygen so that aerobic microorganisms can develop uniformly.
  • The methodologies discussed in this paper employed the following techniques.

10. Pile size and porosity of the material

  • In the sections on passive composting of manure piles and turning windrows, the size of the pile is discussed in detail. When the pile or windrow is very huge, anaerobic zones form in its centre, hence slowing the process in these areas.
  • Too-small heaps or windrows may not generate a high enough temperature to evaporate moisture, destroy pathogens and weed seeds, and remove excess moisture.
  • The appropriate size of piles and windrows must also take into account the physical quality (porosity) of the materials and the method of pile formation.
  • While porous materials allow for larger heaps, heavy loads should not be placed on top, and materials should be kept as loose as possible.
  • Climate also plays a role. In order to minimise heat loss, larger stacks are appropriate for cold weather. In a warmer environment, however, the same piles may overheat and, in extreme situations (75 °C and above), catch fire.

11. Ventilation

  • Ventilation is complementary to efforts to optimise pile size. Diverse ventilation methods exist. The simplest way is punching many holes in the pile.
  • The high temperature method of Chinese rural composting entails placing a number of bamboo poles into the heap and then removing them a day later, leaving the heap with air holes.
  • More air is supplied to the base of the pile, where O deficit occurs most frequently, to increase aeration. In addition to the previously described vertical poles, Ecuadorian on-farm composting utilises a lattice of old branches at the pile’s base to increase the pile’s surface area in contact with the air. In warm seasons, the composting duration is shortened to two to three months.
  • This technique is also utilised in the quick composting process created by the Institute of Biological Sciences (IBS) in the Philippines, where the platform must be elevated 30 centimetres above the ground.
  • The passively aerated wind-rows technology employs a more complex technique. It involves incorporating perforated pipes within the pile. As the pipe ends are opened, air flow is induced and oxygen is continuously delivered to the pile.
  • The aerated static pile method takes this aeration system one step further; a blower provides air flow to create negative pressure (suction) within the pile, and outside air is provided.

12. Turning

  • Turning is the only method for increasing aeration once the pile is established and decomposition has begun. Turning frequency is critical for composting time.
  • The Indian Bangalore method requires six to eight months to develop, whereas the Indian Coimbatore method (turning once) and the Chinese rural composting pit method (turning three times) require only four and three months, respectively.
  • The Berkley quick composting method, which requires daily turning to complete the process in two weeks, is an extreme example.
  • In certain instances, turning not only distributes air throughout the pile, but also prevents overheating by eliminating all microorganisms and halting decomposition. However, excessive rotation may result in a decrease in temperature.

13. Inoculation

  • Some composters find that greater aeration is sufficient for increased microbial activity, while others may require inoculation with microorganisms.
  • Composting inoculum species are predominantly fungus, including Trichoderma sp. (IBS fast composting and composting weeds) and Pleurotus sp (composting Coir Pith and composting weeds).
  • This article also contains information on “effective microorganisms” (EMs) (EM-based quick compost production process). The inoculums are an economical option for both farmers with limited resources and those with market access.
  • Using inoculums collected from compost pits (pit method of the Indian Indore method), acquiring the commercial product and multiplying it on the farm (EM-based rapid compost production process), and utilising native inoculums acquired from soils or plant leaves could minimise production costs.

14. Supplemental nutrition

  • Frequently, the approaches described above must be supplemented by the administration of nutrients. To adjust a high C:N ratio, one of the most typical approaches is to use inorganic fertilisers, notably nitrogen.
  • Similarly, P is sometimes used since the C:P ratio of the material mixture is also seen crucial (the ratio should be between 75:1 and 150:1). Molasses is commonly used for this purpose.

15. Shredding

  • Downsizing, or breaking up the resources, is a tried-and-true method that is commonly utilised. It enhances the accessible surface area for microbial action and improves aeration.
  • This technique is especially effective and essential for tougher materials such as wood.

16. Other measures

  • The practise of adding lime is one example of additional steps stated in this document. Lime is believed to degrade the lignin structure of plant materials and increase the population of microorganisms.
  • In certain instances, however, liming is not advised since the pile may become excessively alkaline, resulting in a substantial N loss.

17. Location

  • The optimal site for compost is a dry and shady area. If you live in a wet region, avoid storing your compost pile or bin under eaves or in low-drainage areas, as the compost may become overly wet.
  • If you reside in a sunny area, locate a shady position for your plants so they don’t dry out too quickly and you don’t have to water them frequently.
  • To begin, add tiny layers of alternating greens and browns, concluding with a layer of browns. (You can continue to add materials until you reach the optimal height of three feet.) If necessary, wet the compost pile as you layer.
  • Then, let the pile alone for four days to allow initial decomposition to commence, following which you may frequently aerate your pile or bin by turning it with a pitchfork or garden fork and monitoring the moisture level on a regular basis.

18. Size

  • The recommended size for a compost container or pile is 3 feet cubed. To generate a high enough temperature for aerobic organisms to survive, a substantial amount of waste is necessary.
  • However, heaps greater than 5 cubic feet may not enable sufficient air to reach the decomposers in the middle and may be more difficult to turn.
  • Before putting larger food or yard scraps to your bin or pile, chop them into smaller bits. The rate of decomposition is proportional to the size of the fragments. A decent rule of thumb is to not include items that are thicker than a finger.

19. Surface area

  • The increased surface area of smaller raw material particles makes nutrients and energy more accessible to microbes.
  • However, smaller particles might diminish the air space inside the composting mass, necessitating a balance; particle sizes ranging from 18 to 2 inches in diameter often give satisfactory results.

20. Retention time

  • The amount of time necessary to turn raw materials into compost is dependent on the six parameters listed above.
  • Proper moisture content and C:N ratio, as well as frequent aeration, lead to the quickest composting time.
  • If there is insufficient moisture, low temperatures, a high C:N ratio, large particles, a high proportion of woody materials that are resistant to decomposition, and insufficient aeration, the process will be hindered.
  • Depending on the process and materials, active composting can last between two weeks and nine months; curing typically takes an additional one to four months. The required composting period is ultimately determined by the planned application of the compost.

What to compost

  • Fruits and vegetables
  • Eggshells
  • grinds for coffee and filters
  • Tea bags
  • Nut husks
  • newspaper, paper, and cardboard shredded
  • Yard waste consisting of grass, leaves, branches, and twigs
  • Houseplants
  • Forage and straw
  • Sawdust
  • Woodchips
  • Rags of cotton and wool
  • Lint from dryers and vacuum cleaners
  • Fur and hair
  • Ashes from the fire

What not to compost

  • Certain types of tree leaves and twigs, such as those of the black walnut, can be toxic to plants due to the compounds they produce.
  • Coal and coal ash, as they may include plant-harming chemicals.
  • Dairy products, eggs, fats and oils, as well as meat or fish bones and leftovers, due to the possibility for odour problems that attract insects and rodents.
  • Avoid planting diseased or insect-infested plants, as the disease or insects may survive and spread to healthy plants.
  • Pet waste (including dog and cat excrement and used cat litter) may include parasites, bacteria, or viruses that are dangerous to humans.
  • As the pesticides could harm composting organisms, yard trimmings treated with chemical pesticides cannot be composted.

Role of Microorganisms in Composting

Bacteria

  • Bacteria are the smallest and most abundant organisms in compost, comprising 80 to 90 percent of the billions of bacteria typically present in one gramme of compost.
  • Bacteria are primarily responsible for breakdown and heat production in compost. They are the most nutritionally varied group of compost organisms, utilising a wide array of enzymes to chemically decompose a variety of organic substances.
  • Bacteria are unicellular and can take the form of rod-shaped bacilli, spherical cocci, or spiral-shaped spirilla. Many are motile, which means that they can move under their own power.
  • At the onset of the composting process (0 to 40 degrees Celsius), mesophilic bacteria predominate. The majority of these organisms are also found in topsoil.
  • Above 40 degrees Celsius, thermophilic bacteria take over the compost. Bacillus-affiliated microorganisms dominate the microbial communities at this phase. The diversity of bacilli species is rather high at temperatures between 50 and 55 degrees Celsius, but it falls substantially at temperatures of 60 degrees Celsius or above.
  • When environmental conditions become unfavourable, bacilli create endospores, which are highly resistant to heat, cold, dryness, and lack of sustenance.
  • They are pervasive throughout the natural world and become active anytime environmental conditions are favourable.
  • Bacteria of the genus Thermus have been isolated at the highest compost temperatures. Composters often question how microorganisms that can endure the high temperatures observed in active compost arose in nature.
  • Thermus bacteria were initially discovered in Yellowstone National Park’s hot springs and may have evolved there.
  • In nature, thermophilic conditions also exist in deep sea thermal vents, manure droppings, and accumulations of decomposing vegetation, all of which have the same circumstances as a compost pile for heating up.
  • Once the compost has cooled, mesophilic bacteria prevail once more. The amount and types of mesophilic microorganisms that recolonize compost as it grows are dependent on the spores and organisms present in the compost as well as the surrounding environment.
  • In general, the longer the curing or maturation process, the greater the diversity of the microbial population that it supports.

Actinomycetes

  • Actinomycetes, creatures that resemble mushrooms but are actually filamentous bacteria, are responsible for soil’s distinctive earthy odour. They lack nuclei like other bacteria, but develop multicellular filaments like mushrooms.
  • Complex organic compounds such as cellulose, lignin, chitin, and proteins are degraded significantly by these organisms during composting. Their enzymes allow them to chemically degrade resistant detritus including woody stems, bark, and newspaper.
  • Some species develop during the thermophilic phase, but others become significant during the cooler curing phase, when only the most durable compounds survive in the last phases of humus formation.
  • Actinomycetes produce long, thread-like filaments with branching that resemble grey spider webs extending across compost. These filaments are most frequently observed in the outer 10 to 15 centimetres of the compost pile near the conclusion of the composting process. Occasionally, they form as circular colonies that develop gradually in diameter.

Fungi

  • Fungi, which include moulds and yeasts, are responsible for the breakdown of numerous complex plant polymers in soil and compost.
  • Fungi are vital in compost because they degrade stiff material, allowing bacteria to continue the decomposition process once the majority of the cellulose has been consumed.
  • They can attack organic leftovers that are too dry, acidic, or poor in nitrogen for bacterial breakdown. They spread and multiply rapidly by forming many cells and filaments.
  • The majority of fungus are categorised as saprophytes because they feed on dead or dying matter and derive their energy from decomposing the organic materials of deceased plants and animals.
  • During both the mesophilic and thermophilic phases of composting, fungi are abundant. When temperatures are high, most fungus inhabit the compost’s outer layer. On the surface of compost, compost moulds develop both as invisible filaments and as grey or white fuzzy colonies.

Protozoa

  • Protozoa are one-celled tiny creatures.
  • They are present in compost’s water droplets but play a minimal function in breakdown.
  • Protozoa derive their nutrition from organic materials in the same manner as bacteria, but they are also secondary consumers, consuming bacteria and fungi.

Rotifers

  • Rotifers are minute multicellular organisms found in compost films of water. They consume organic materials, as well as bacteria and fungi.

Other Organisms

  • Ants – Ants are omnivorous, consuming mushrooms, seeds, sweets, and other insects, among other things. They contribute to the process of composting by introducing fungi and other creatures into their nests. As they labour, ants can enrich compost with phosphorus and potassium by redistributing minerals.
  • Millipedes – Millipedes have segmented bodies with two pairs of walking legs on each segment (except the front few segments). Millipedes aid in decomposition of plant matter by feeding on soft, rotting plants. They will form a ball when threatened.
  • Centipedes – Centipedes are segmented, flat worms with one set of legs in each segment. They are third-level consumers that feed primarily on insects and spiders.
  • Sow bugs – Sow bugs have a flat, oval body with ten pairs of legs and distinct segments. They are primary consumers that consume decaying wood and other decaying vegetation. Comparable to sow bugs in appearance, pill bugs curl into a ball when disturbed.
  • Springtails – Springtails are little insects characterised by their capacity to leap in response to a disturbance. They rarely exceed one-fourth of an inch in length and range from white to blue to black in hue. Springtails mostly consume fungus, although they also consume moulds and rotting plants.
  • Flies – Flies are two-winged insects that feed on nearly all forms of organic matter. In addition, they transport germs through the air and deposit it wherever they land. Although flies are typically not a problem with compost piles, you can reduce their population by placing a layer of dry leaves or grass clippings on top of the pile. Additionally, bury food scraps eight to twelve inches deep within the mound. Temperatures that are thermophilic destroy fly larvae. Mites aid in limiting the population of fly larvae.
  • Beetles – The insects known as beetles have two pairs of wings. The rove beetle, the ground beetle, and the feather-winged beetle are frequent types seen in compost piles. The feather-winged beetle consumes spores of fungi. Immature grubs feed on rotting plants. Adult rove and ground beetles feed on slugs, snails, and other small creatures.
  • Snails and slugs – Snails and slugs are slow-moving mollusks. Snails feature a shell with a spiral shape, an unique head, and retractable legs. Slugs lack a shell and are bullet-shaped with antennas on the front of their bodies. They mostly consume living plant matter, but will also consume plant trash. Check for them in finished compost before applying it to your garden, since their presence could be detrimental.
  • Spiders – Arachnids are third-level consumers with eight legs that feed on insects and tiny invertebrates. They can be quite useful for pest control in the garden.
  • Earthworms – Of the big physical decomposers in a compost pile, earthworms are the most essential. In their gizzards, earthworms digest organic stuff with the aid of small stones. Their digestive secretions are loaded with hormones, enzymes, and other fermenting compounds that continue the process of decomposition. The worms leave behind dark, fertile castings. Each day, a worm can produce its own weight in castings. These castings are abundant in plant nutrients such as nitrogen, calcium, magnesium, and phosphorus that would otherwise be inaccessible to plants. Earthworms thrive in compost and significantly improve its quality. Either the presence of earthworms in compost or soil indicates healthy microbial activity.

Types of Composting

1. Onsite Composting

  • Organizations who intend to compost small quantities of food scraps can do it on-site.
  • Composting can considerably decrease the amount of food that is discarded as waste. On-site composting of yard trimmings and small amounts of food scraps is possible.
  • Animal products and huge amounts of food waste are incompatible with on-site composting.
  • Changes in climate and seasons will have little impact on on-site composting. Changes, such as the approach of the rainy season, may necessitate minor alterations.
  • Food leftovers must be properly disposed of to prevent odours and the attraction of insects and animals.
  • On-site composting requires minimal time and equipment. Education is essential. To encourage households and businesses to compost on their own sites, local communities may provide composting demonstrations and seminars.
  • Composting can take up to two years, however manual rotation can shorten the duration to three to six months.
  • Due to the presence of weed and grass seeds, however, compost should not be utilised as potting soil for houseplants.
  • Leaving grass clippings on the lawn is referred to as “grasscycling.” Similar to composting, these cuttings will disintegrate naturally and restore some nutrients to the soil.
  • You can collect leaves and use them as mulch to maintain moisture around trees and shrubs.

2. Vermicomposting

  • To generate compost, red worms in bins consume food scraps, yard clippings, and other organic waste.
  • Worms transform this material into castings, a high-quality compost. Worm bins are simple to manufacture and commercially available.
  • One pound of mature worms (about 800 to 1,000 worms) can consume up to a half-pound of organic matter daily. The size of the bins can correspond to the amount of food waste that will be transformed into castings.
  • Typically, three to four months are required to make useable castings. The castings are suitable for use as potting soil.
  • Worm tea, the other output of vermicomposting, is a high-quality liquid fertiliser for houseplants and gardens.
  • Ideal for residents of apartments and small offices.
  • Vermiculture can be used in schools to teach youngsters about conservation and recycling.
  • It is essential to maintain the worms alive and healthy by giving the ideal environment and enough food.
  • Prepare bedding, bury waste, and separate worm castings from worms.
  • Worms are sensitive to climate change.
    • Extreme heat and intense sunshine are detrimental to the health of the worms.
    • The optimal temperatures for vermicomposting vary from 55 to 77 degrees Fahrenheit.
    • In hot, dry regions, the trash can should be placed in the shade.
    • Indoor vermicomposting can prevent many of these issues.

3. Aerated (Turned) Windrow Composting

  • Composting in aerated or rotated windrows is suitable for enormous volumes, such as those created by entire communities, collected by local governments, and processed by high-volume food-processing firms (e.g., restaurants, cafeterias, packing plants).
  • It will produce a substantial amount of compost, which may require marketing support. Local governments may wish to provide compost to citizens for a nominal or no fee.
  • This technique of composting includes arranging organic waste into rows of long piles called “windrows” and regularly aerating them by turning them manually or mechanically.
  • The optimal pile height and width are four to eight feet and fourteen to sixteen feet, respectively. This size of pile generates sufficient heat and maintains temperatures. It is tiny enough to allow oxygen to reach the centre of the windrow.
  • This approach permits the composting of large quantities of different wastes, such as yard trimmings, oils, liquids, and animal byproducts (such as fish and poultry wastes).
  • Composting in windrows frequently necessitates huge tracts of land, durable equipment, a constant supply of manpower to maintain and operate the facility, and the willingness to experiment with different material combinations and turning frequencies.
  • In a warm, arid region, windrows are occasionally covered or sheltered to avoid water evaporation.
  • During rainy seasons, the shape of the pile can be altered so that water runs off the top rather than being absorbed.
  • Composting in windrows can operate in frigid areas. Frequently, the exterior of a windrow may freeze, while its interior can reach 140° F.
  • Leachate is a byproduct of the composting process. This can contaminate groundwater and surface water supplies in the area. It must be gathered and treated.
  • Composting in windrows is a large-scale activity that may be subject to regulatory enforcement, zoning, and siting regulations. The microbial and metal content of compost should be determined in a laboratory.
  • Similarly, odours must be managed. The public should be informed of the operation and provided with a means to address any animal or odour complaints.

4. Aerated Static Pile Composting

  • Aerated static pile composting generates compost comparatively quickly (within three to six months).
  • It is intended for a reasonably homogeneous mixture of organic waste and works well for larger generators of yard trimmings and compostable municipal solid trash (e.g., food scraps, paper products), such as municipalities, landscapers, and farms.
  • However, this method does not work well for composting animal byproducts or food processing grease.
  • In the process of aerated static pile composting, organic waste is mixed in a big pile. To aerate the pile, layers of loosely heaped bulking agents (e.g., wood chips, shredded newspaper) are added so air may flow from the bottom to the top.
  • The piles can also be positioned over a network of pipes that deliver or remove air from the pile. Timers or temperature sensors may be used to trigger air blowers.
  • In a warm, arid area, it may be required to cover or protect the pile to avoid the evaporation of water.
  • The centre of the pile will maintain its warmth in the cold. Using passive air flow rather than active rotation may make aeration more challenging. Occasionally, placing the aerated static piles indoors with enough ventilation is also a possibility.
  • Since there is no physical turning, constant monitoring is required to guarantee that the exterior of the pile reaches the same temperature as the centre.
  • By applying a thick layer of completed compost over the pile, any odours may be mitigated. If the air blower removes air from the pile, filtering the air via a biofilter built from completed compost will also eliminate any odours.
  • Purchase, installation, and maintenance of equipment such as blowers, pipelines, sensors, and fans may necessitate a large financial investment and technical support.
  • A controlled air supply makes it possible to create enormous piles that use less area than the windrow approach.

5. In-Vessel Composting

  • In-vessel composting can process enormous quantities of trash without requiring as much room as windrow composting, and it can accommodate nearly any sort of organic waste (e.g., meat, animal manure, biosolids, food scraps).
  • This process involves placing organic materials in a drum, silo, concrete-lined trench, or similar apparatus. This enables effective management of environmental factors such as temperature, humidity, and ventilation.
  • For the purpose of aerating the substance, it is mechanically twisted or mixed. The size and capacity of the vessel is variable.
  • This technique produces compost in a matter of weeks. Due to the requirement for the microbial activity to balance and the pile to cool, it will take a few more weeks or months before it can be used.
  • Some are small enough to fit in the kitchen of a school or restaurant.
  • Some are comparable to the size of a school bus in size. Large food processing facilities frequently employ them.
  • This technology can be used throughout the year due to the careful, and frequently electronic, climate control.
  • Use is possible in severely cold conditions with insulation or indoors.
  • There is hardly any odour or leachate created.
  • This approach is costly and may necessitate technical skill for proper operation.
  • Utilizes significantly less area and effort than windrow composting.

Composting Steps – layring

The suggested approach for starting a compost pile is layering. Layering is comparable to preparing lasagna in that consistent, thin layers of material are added in a repetitive pattern. Once the compost pile is active, more materials can be added to the centre of the pile or mixed in when the pile is turned.

Begin your compost pile on bare ground, after removing any sod or existing plants. Contact with soil will offer the necessary bacteria for composting. Do not set the pile on asphalt or concrete. If poor drainage under the pile is a concern, you may also place a pallet underneath it.

Compost Layer 1

Add a 6- to 8-inch layer of mixed brown and green organic debris. Do not pack the items, as this restricts airflow and oxygen that germs require.

Compost Layer 2

Add a starter material, such as animal manures (see the allowed types list), fertilisers, or commercial starters. By providing nitrogen for the bacteria and other microbes, these materials assist to heat the pile. Choose one of the options below:

  • 1- to 2-inch coating of fresh manure from a grain-eating animal, 1 cup of 10-10-10 or 12-12-12 fertiliser per 25 square feet, or a commercial starter according to the instructions on the label.

Compost Layer 3

Add a 1- to 2-inch layer of finished garden compost or topsoil. This is performed in order to introduce microorganisms into the pile. Avoid using soil that has been recently treated with insecticides, as well as sterile potting soil.

Importance of Composting

1. Reduces the Waste Stream

  • Composting is an excellent method for recycling the organic waste we produce at home. Together, food scraps and yard garbage account for more than 28 percent of our waste.
  • Not only is food waste a substantial environmental burden, but its processing is also expensive.
  • The ability to compost at home allows us to remove some of this trash from landfills and transform it into something useful for our yards.

2. Cuts Methane Emissions From Landfills

  • Typically, when organic matter decomposes, it undergoes aerobic decomposition, meaning it is broken down by oxygen-dependent microbes.
  • When biodegradable waste is placed in a landfill, it is buried behind a mountain of other trash, cutting off the decomposers’ oxygen source.
  • The trash is then subjected to anaerobic decomposition, where it is broken down by organisms that can survive without oxygen.
  • Biogas is produced as a byproduct during anaerobic decomposition. Both methane and carbon dioxide are powerful greenhouse gases, but methane is 28 to 36 times more effective than carbon dioxide at trapping heat in the atmosphere over a century.
  • Although most modern landfills include methane capture systems, these systems do not capture all of the gas; landfills remain the third-largest source of methane emissions produced by humans.
  • Due to the landfill-centric architecture of our solid waste system, only about 6 percent of food waste is composted. However, states, towns, and individual businesses and vendors can pioneer zero-waste efforts to raise composting and recycling rates within their boundaries and prevent trash generation.

3. Improves Soil Health and Lessens Erosion

  • Compost is an indispensable tool for enhancing agricultural systems on a broad scale. Compost includes three essential plant nutrients: nitrogen, phosphorus, and potassium.
  • In addition, it contains trace quantities of calcium, magnesium, iron, and zinc.
  • Composting provides an organic alternative to the use of synthetic fertilisers that contain hazardous chemicals. Compost can boost the soil’s water retention capacity, productivity, and resilience, according to research.

4. Conserves Water

  • The addition of organic matter increases the soil’s ability to hold water. In fact, each 1 percent increase in soil organic matter increases water retention by 20,000 gallons per acre. By utilising compost to promote healthy soil, farmers can reduce their water consumption while still achieving greater crop yields compared to farming on damaged soil.

5. Reduces Personal Food Waste

  • The most effective method to reduce consequences from food waste is to prevent waste from occurring in the first place, therefore NRDC uses its Save the Food campaign and other tools to educate people on how to shop for, cook, and store food to avoid waste.
  • Nevertheless, even if we do all necessary to reduce food waste, there will still be unusable food scraps (e.g., a banana peel). Composting is an excellent alternative to throwing away these waste products.

What is Windrow composting?

  • This is the process of producing compost from organic materials or biodegradable waste, such as animal manure and agricultural wastes.
  • This method is suitable for manufacturing big quantities of compost. Due to poor waste management procedures in the world, vegetable waste with a high moisture content and a biodegradable nature are the leading cause of environmental problems.
  • Consequently, composting and vermicomposting could be regarded as the most effective alternative processes for treating these organic fractions.
  • Windrow composting entails the aerobic bioconversion of organic waste to stable compost with the production of heat, water vapour, and carbon dioxide (CO2), whereas pile composting can only be employed for limited amounts of input materials.
  • At the outset of the Windrow composting process, however, significant volumes of materials can be composted in windrows measuring between 2 and 4 metres in width and 2 to 3 metres in height.
  • The use of windrow compost or any other compost can significantly reduce the need for ammonia-based fertilisers.

What is Bio Compost?

  • The bio-compost consists of decomposed and recycled plant material used as fertiliser or manure.
  • Bio-compost is regarded as the most important component of organic farming. It is nutritionally dense.
  • Bio-compost is an organic, eco-friendly fertiliser. Bio-compost is produced from decomposed and enriched sugar industry waste containing a variety of plants and human-friendly bacteria and fungi.

Aerobic Composting 

  • Aerobic composting is the breakdown of organic materials by oxygen-dependent microbes.
  • The bacteria primarily responsible for composting are naturally existing and reside in the organic matter’s surrounding wetness.
  • Airborne oxygen diffuses into the wetness, where it is absorbed by bacteria. As a result of aerobic digestion, the byproducts are heat, water, and carbon dioxide (CO2).
  • CO2 can be categorised as a greenhouse gas, but because it is a byproduct of composting, it is not counted as an emission.

The aerobic composting process 

  • The process of aerobic composting begins with the development of the pile. In many instances, the temperature reaches 70-80 °C during the first several days.
  • Initially, mesophilic organisms (optimum growth temperature range = 20-45 °C) proliferate fast on carbohydrates and amino acids that are easily available. They produce heat through their metabolism and elevate the temperature to a degree where their own activities are inhibited.
  • Then, a few thermophilic fungi and several thermophilic bacteria (optimum growth temperature range = 50-70 °C or higher) continue the process by increasing the material’s temperature to at least 65 °C.
  • This peak heating phase is crucial to the compost’s quality because the heat eliminates bacteria and weed seeds.
  • The active composting phase is followed by a curing phase, during which the temperature of the pile steadily falls.
  • The beginning of this phase is determined when turning the pile no longer reheats it. Another type of thermophilic fungi begins to grow at this stage.
  • These fungi play a significant role in the degradation of cellulose and hemicellulose plant cell wall components.
  • Curing the compost mitigates the dangers associated with utilising immature compost, such as nitrogen (N) deficit, oxygen (O) deficiency, and the harmful effects of organic acids on plants.
  • Eventually, the temperature returns to the surrounding environment.
  • Upon completion of the composting process, the pile is more homogenous and less biologically active, although mesophilic organisms recolonize the compost. The colour of the material transforms from dark brown to black.
  • The particles shrink in size and acquire a uniform, soil-like consistency. The process raises the amount of humus, decreases the ratio of carbon to nitrogen (C:N), neutralises the pH, and boosts the material’s exchange capacity.
The aerobic composting process 
The aerobic composting process 

Solid line = temperature; broken line = mesophilic fungi population; dotted line = thermophilic fungi population; left y-axis = fungal populations (logarithm of colony forming units (cfu) per gram of compost plated onto agar); right y-axis = temperature in centre of compost. a, b, c and d = heating phases. Source: http://helios.bto.ed.ac.uk/bto/microbes/thermo.htm

Anaerobic Composting

  • Anaerobic composting is the breakdown of organic matter by microorganisms that do not need oxygen to thrive.
  • In an anaerobic composting system, the bulk of the initial material’s chemical energy is released as methane.
  • The technique generates very strong scents and just a little amount of heat, so decomposition takes significantly longer and does not reach temperatures high enough to safely destroy plant infections, weeds, and seeds. Usually, external or artificial heat is provided to counteract these constraints.

Suitable Water Requirements For Composting

  • For aerobic composting (composting that takes place in the presence of oxygen), the maximum moisture content should be maintained at a level that enables aerobicity during the whole composting process.
  • Materials containing more fibres, such as straw and wood chips, can hold a higher moisture content (over 60%) without generating anaerobic conditions, but materials with less structural strength, such as paper, grass clippings, soil, and manure, should contain less total moisture.
  • It is often assumed that the optimal moisture content for on-farm composting is between 50 and 60 percent by weight, despite the fact that the ideal moisture content of the compost pile changes depending on the pile ingredients. When a handful of blended materials is squeezed, it should feel moist.
  • A moisture content that is too low can deprive microorganisms of the water required for their metabolism, so slowing down the composting process.
  • The pore spaces in the compost pile will be filled with water rather than air if the moisture level is too high, resulting to anaerobic conditions. Moisture also influences pile temperature.
  • Dryer piles tend to heat and cool more quickly than their wetter counterparts. The ideal moisture content can be achieved by blending materials with varying moisture percentages.
  • If the original ingredients are too dry to attain the ideal moisture level, additional water can be added during the blending process.
  • A laboratory for assessing manure and compost can detect moisture. Moisture metres are also available from equipment dealers.
  • However, a more practical and straightforward method is to employ the “squeeze test.” Squeeze a handful of the liquid using a gloved hand. It is too wet if more than a few drips of water come out. If it appears to be extremely dry, moisture must be added.

Suitable Ph Levels For Composting

  • The pH, a measure of the acidity or alkalinity of compost pile materials, influences the growth and activity of microbes and the destiny of N compounds.
  • The ideal pH range for bacteria is 6.0 to 7.5 while for fungus it is 5.5 to 8.0. When the pH of compost surpasses 7.5, ammonia gaseous losses are more likely to occur.
  • Certain substances, like dairy manure and paper production wastes, can increase pH, whereas food processing wastes can decrease pH.
  • However, maintaining pH within an ideal range is challenging and is typically avoided. Throughout the heap and during the composting process, the pH fluctuates.
  • The pH of finished compost typically falls between 6.5 and 7.5. It is possible to measure pH by sending samples to a laboratory.

Suitable Temperature Levels For Composting

  • Temperatures within compost piles influence the growth and activities of microorganisms and, consequently, the rate at which raw materials disintegrate.
  • Higher temperatures accelerate the decomposition of organic matter, destroy weed seeds, and eliminate infections. However, temperatures above 160 degrees Fahrenheit can impede microbial activity.
  • For composting, thermophilic temperatures (105 to 160 F) are the most effective and efficient. The ideal temperature range is estimated to be between 130 and 150 F.
  • Throughout the composting process, the temperature should be periodically monitored using a thermometer and adjusted as necessary.
  • Common techniques for modifying temperatures include aeration, turning, altering the moisture content and size of the piles, and aeration.

What Is The Oxygen Demand?

  • Composting can occur both aerobically and anaerobically. Nevertheless, aerobic composting is the most effective method.
  • Aerobic microorganisms can thrive at O2 concentrations as low as 5%, despite the fact that the environment contains 21% O2, although O2 values greater than 10% are regarded optimum in compost piles.
  • As bacteria oxidise carbon for energy, they consume O2 and release carbon dioxide. As the compost pile’s microbial activity grows, more oxygen will be consumed.
  • Without enough oxygen, the process will become anaerobic and emit foul odours. To keep aerobic organisms alive, compost must be aerated either passively or actively.
  • The most frequent form of aeration for on-farm composting is material turning. Oxygen monitoring equipment is accessible but pricey.
  • Temperature, smells, and moisture are simple to measure and provide an excellent indication of active decomposition and sufficient ventilation.
  • A noticeable bad stench (e.g., rotten eggs) typically indicates anaerobic conditions have developed in a compost pile.

Advantages of Composting

  • Composting is beneficial for enriching soil, retaining moisture, and preventing plant diseases and pests.
  • It decreases the demand for synthetic fertilisers.
  • Reduces landfill methane emissions and reduces carbon footprint.
  • When organic materials, such as sawdust or straw, are applied directly to the soil, nitrogen availability often decreases. Composting mitigates this effect.
  • Composting can also be used to recycle kitchen trash, crop leftovers, weeds, and manures. Composting is possible with numerous types of local organic waste, including apple pumice, lakeweeds, leaves, and grass clippings.
  • Due to ammonia loss during the composting process, compost has less nitrogen than biosolids from other stabilisation methods. However, nitrogen in compost is released slowly and is available to plants over an extended period, which is more in line with plant absorption requirements.
  • Windrow and aerated static pile composting require rather wide spaces, and odour control is a prevalent issue.
  • The windrow and aerated static pile composting processes are affected by ambient temperature and meteorological variables.

References

  • https://www.agrifarming.in/what-is-compost-types-of-compost-compost-methods
  • https://www.fast-growing-trees.com/pages/factors-that-affect-composting
  • http://ecoursesonline.iasri.res.in/mod/page/view.php?id=621
  • https://www.nrdc.org/stories/composting-101
  • https://www.livescience.com/63559-composting.html
  • https://www.sciencedirect.com/topics/engineering/composting-process#:~:text=Composting%20is%20a%20process%20that,material%20in%20presence%20of%20air.
  • https://extension.illinois.edu/soil/composting
  • https://en.wikipedia.org/wiki/Compost
  • https://www.epa.gov/sustainable-management-food/types-composting-and-understanding-process
  • https://home.howstuffworks.com/composting.htm
  • https://www.ecepl.com/organic-waste-composting-process/
  • https://www.vineyardteam.org/files/resources/Commercial%20compost%20production%20process.pdf
  • https://directcompostsolutions.com/8-methods-composting/
  • https://content.ces.ncsu.edu/large-scale-organic-materials-composting
  • http://compost.css.cornell.edu/microorg.html
  • https://bmcmicrobiol.biomedcentral.com/articles/10.1186/1471-2180-10-94
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Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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