Composting is currently the most environmentally sustainable approach to deal with organic waste and is the foundation of a more circular economy.
Composting is the natural, biological decay of organic matter by fungi, bacteria, worms, and other organisms. Successful composting involves managing the decomposition process so that it is relatively quick, clean, and safe.
Poorly managed composting may produce foul odours, encourage pests and vermin, spread plant and animal pathogens, and cause environmental contamination.
Organisms that decompose organic matter require the following fundamental sources and conditions to maximise their processes and efficiency:
- A suitable ‘food’ source
- A suitable temperature
- Oxygen (if decomposing aerobically)
Biological decomposition of organic matter can occur in either an aerobic (oxygen-rich) or anaerobic (oxygen-poor) environment.
Commercial composting is large-scale composting which is designed to handle a very high volume of organic waste. It optimises the process to ensure rapid biodegradation of organic material.
Few cities in the US, have already taken the lead to composting over the last decade. The goal initiated in San Francisco in 2002 was diverting 75% of its waste from landfills by 2010 and achieving “zero waste” by 2020.
The process of composting
The composting process includes four primary components: organic matter, moisture, oxygen, and bacteria.
Organic matter includes plant materials and some animal manures.
Organic materials used for composting consist of a mixture of brown organic material such as dried leaves, twigs, and manure and green organic material such as lawn clippings and fruit rinds.
Brown materials supply carbon, while green materials produce nitrogen. The best proportion is 1 part green to 1 part brown material.
Shredding, chopping, or mowing those materials into smaller pieces helps speed up the composting process.
For piles with mostly brown material (dead leaves), adding a handful of commercial 10-10-10 fertiliser to supply nitrogen speeds the composting process.
Moisture is crucial to help the composting process.
Compost should be similar to the wetness of a wrung-out sponge.
The materials will decompose very slowly if the pile is too dry. Adding water during dry periods or an enormous amount of brown organic material can help fasten the process.
If the pile is too wet, add dry brown organic materials. Or, turn the pile and mix the materials.
Oxygen is expected to help the breakdown of plant material by bacteria.It is crucial to turn the compost pile so that materials at the edges are brought to the pile’s centre to receive oxygen.
Turning the pile is essential for complete composting and odour controlling.
A span of two weeks is required before turning the pile to allow the centre of the pile to heat up and decompose.
Once the pile has cooled in the centre, decomposition of the materials has occurred. Regular turning will hasten the composting process.
Bacteria and other microorganisms are essential in the composting process.
The bacteria present will break down the plant material into useful compost for the garden by supplying organic materials, water, and oxygen.
As the bacteria decompose the materials, it releases heat that is concentrated in the centre of the pile. Adding finished compost supplies more bacteria and speeds the composting process.
In addition to bacteria, larger organisms like insects and earthworms are active composters. These organisms can break down large materials in the compost pile.
There are three fundamental stages in the composting process in which various types of microorganisms rise.
The first stage is usually only several days in length, during which Mesophilic microorganisms (microorganisms that thrive in temperatures of about 20°C to 45°C) start to break down the biodegradable compounds physically.
Heat is a natural result of this process, and temperatures quickly rise to over 40°C.
Mesophilic microorganisms are substituted by thermophilic microorganisms (microorganisms that thrive in higher temperatures) during the second stage, which can last a few months.
The thermophilic microbes work to separate the natural materials into more refined pieces. Higher temperatures are more helpful for separating proteins, complex carbohydrates, and fats.
Also, during the second stage, temperatures keep on rising. If not closely watched, the compost pile can get so hot that it can eventually kill off all the helpful microorganisms.
Procedures such as aeration and turning over the compost pile help keep temperatures about 65°C, as well as give extra oxygen and new hotspots for the thermophilic microorganisms to break down.
The third stage, which usually lasts a few months, begins when the thermophilic microorganisms utilize the available supplies.
At this stage, temperatures begin to drop enough for mesophilic microorganisms to resume control of the compost pile and finish breaking down the remaining organic matter into usable humus.
What can be put in a compost?
Good things to compost include fruit waste, vegetable peels, tea bags, and grass cuttings. These are quick to break down and provide necessary nitrogen as well as moisture.
It’s also acceptable to include cardboard egg boxes, dried leaves, and scrunched up papers. These are slower to decay but provide vital fibre and carbon and also permit significant air pockets to form in the mixture. Crushed eggshells can be included to add helpful minerals.
Methods of composting
There are several methods of composting that are commonly used: :
Organisations that will compost limited quantities of wasted food can compost onsite.
Yard trimmings and small quantities of food scraps can be composted onsite. Animal products and large amounts of food scraps are not suitable for onsite composting.
Onsite composting is an opportunity to use wood waste in ways that keep most of the organic material in its original ecological system and enhance conservation.
- Types of Waste and Waste Generators: Onsite composting is suitable for converting yard trimmings and food scraps into compost that can be implemented onsite. This method should not be used to compost animal products or a large number of food scraps.
Households, small commercial foundations, and organisations like universities, schools, and hospitals can leave grass cuttings on the lawn-known as grasscycling. The cuttings will decompose naturally and give back nutrients to the soil. Onsite composters additionally may keep leaves in piles for eventual use as mulch around trees and bushes to hold dampness.
- Climate or Seasonal Considerations: Climate and seasonal fluctuations don’t present considerable challenges to onsite composting because this method includes a small amount of organic excess typically.
- Requirements: Onsite composting requires very little time and equipment.
- Results: The transformation of organic material to compost can take up to two years, but manual turning can considerably rush the process by three to six months. The resulting natural fertiliser can be applied to lawns and gardens to condition the soil and restore nutrients.
Compost should not be used for houseplants because of weed and grass seeds.
Aerated (Turned) Windrow Composting
Organic waste is made into rows of long piles called “windrows” and aerated by turning the pile occasionally by either manual or mechanical methods.
The ideal pile height, which is somewhere in the range of 4 and 8 feet, allows for a pile large enough to generate adequate heat and sustain temperatures yet small enough to enable oxygen to flow to the windrow’s core.
- Types of Waste and Waste Generators: This method can oblige large volumes of mixed wastes, including yard trimmings, oil, fluids, and animal byproducts such as fish and poultry wastes, but only with regular turning and careful monitoring. This method is appropriate for giant quantities, such as that generated by entire communities and gathered by local governments or high volume food-processing businesses like restaurants and cafeterias.
- Climate or Seasonal Considerations: In a warm, dry atmosphere, windrows are covered or put under a shelter to block water from evaporating. In rainy seasons, the shapes of the pile can be modified so that water runs off the top of the pile instead of being absorbed into the pile. Also, windrow composting can operate in cold environments. Often the outside of the pile might freeze, but in its centre, a windrow can reach 60°C.
- Requirements: Windrow composting requires large land plots, vital equipment, a constant supply of labour to maintain and operate the facility, and tolerance to try different things with different materials combinations and turning rates.
- Results: This method will produce massive compost measures, which may need help to market the end-product.
Organic materials are placed into a drum, pit, concrete-lined tube, or similar equipment where the environmental conditions, including temperature, moisture, and aeration-are closely controlled.
The apparatus usually has a component to turn or shake the material for appropriate aeration. In-vessel composters differ in size and volume.
- Types of Waste and Waste Generators: In-vessel composting can handle a lot of waste without occupying too much space. It can also accommodate any natural waste like meat, animal manure, biosolids, and food pieces. Some in-vessel composters can fit into an institution or restaurant kitchen, while others could be big to accommodate large food processing mills.
- Climate or Seasonal Considerations: In-vessel composting can be utilized all year in basically any atmosphere because the environment is carefully controlled by electronic means. This method can also be used in freezing weather if the equipment is insulated or the processing takes place indoors.
- Requirements: In-vessel composters are costly and might need technical assistance to operate accurately.
- Results: Conversion of organic material to compost can take as little as a few weeks. However, once the compost comes out of the vessel, it still requires a few more weeks or months for the microbial activity to stabilise and the pile to cool.
Through this method, red worms or field worms are placed in bins with organic matter to disintegrate it into a high-value compost called castings.
Worm bins are easy to assemble and can be modified to suit the volume of food scraps produced.
- Types of Waste and Waste Generators: Worms eat almost anything in a typical compost pile like food scraps, plants, and paper. Vermicomposting can be ideal for apartment tenants or small offices that want to obtain some of the benefits of composting and decrease solid waste.
- Climate or Seasonal Considerations: Worms are sensitive to fluctuations in climate. Extreme temperatures and direct sunlight are not healthy for the worms. The optimal temperatures for vermicomposting range from 12°C to 23°C.
In hot, dry areas, the bin should be placed under the shade. However, by vermicomposting indoors, many of the problems posed by hot or cold environments can be avoided. The primary constraint is to keep the worms alive and healthy by providing the proper conditions and sufficient food.
- Requirements: Vermicomposting has only a few basic needs, among them: worms, worm bedding such as shredded newspaper or cardboard, and a bin to accommodate the worms and organic matter. The support system includes preparing bedding, covering bins, and separating worms from their casts.
- Results: One pound of mature worms (around 800-1,000 worms) can eat up to half a pound of organic material each day.
It usually takes three to four months for the worms to produce harvestable castings, which can be used as fertilised soil. Vermicomposting likewise creates compost or “worm” tea, a high-quality liquid fertiliser for house plants or gardens.
Aerated Static Pile Composting
In aerated static pile composting, organic waste is combined in one large pile rather than rows.
To aerate the pile, layers of loosely piled building agents like wood chips, shredded newspaper is combined so that air can pass from the base to the highest point of the pile.
The piles can be placed over a network of pipes that deliver air or draw air out of the pile. A timer or a temperature sensor might activate air blowers.
- Types of Waste and Waste Generators: Aerated static piles are reasonable for a generally homogenous blend of organic waste and function well for larger quantity generators of yard trimmings and compostable civil solid waste such as food and scraps, which may include local governments, landscapers, or farms.
However, this method does not work well for composting animal byproducts or grease from food processing industries.
- Climate or Seasonal Considerations: Like windrow composting, in a warm, dry atmosphere, aerated static piles are sometimes covered or put under a shelter to restrict water from evaporating.
In the cold, the core of the pile will hold its warm temperature, but aeration might be more difficult in the cold since this method includes passive air flowing instead of active turning. Some aerated static piles are located indoors with proper ventilation.
- Requirements: This method typically requires blowers, pipes, sensors, and fans, which might involve high costs and technical assistance. Having a controlled supply of air enables large piles, which entail less ground than the windrow method.
- Results: This method creates compost relatively quickly-within 3 to 6 months.
What are commercially compostable products?
A product is commercially compostable when it has the word ‘compostable’ on it. The work requires increased temperatures and specifically formulated microbial conditions to be transformed into beneficial compost.
This is where materials like PLA (polylactic acids) made from a corn-starch or sugar-cane base come into place. These materials hold many of the necessary characteristics of traditional petroleum-based plastics but can be composted at the end of their lives.
For a product to be labelled as compostable, the materials must disintegrate by 90% within 90 days of being in a commercial facility.
Also, the products must create zero toxicity during the degradation process. If it does not meet the requirements, it can’t be certified as compostable.
The difference between home compostable and commercially compostable products
Home composting produces the same results as commercial composting but at a smaller scale. However, it is difficult and could even be impossible to generate ideal conditions at home. It takes continued levels of heat to ensure the breakdown of molecular bonds.
It is difficult to compost fats, oils, grease, meat, fish, and dairy at home because it is tough to generate enough heat in a pile.
There is not enough carbon and yard waste to absorb moisture and break items down correctly.
Attempting to compost those items at home increases the likelihood of attracting unwanted pests like rats, skunks, possums, and raccoons. Those animals are attracted to the smell and can turn the efforts into a burden.
Opting to send the food waste to an industrial composting facility is a convenient, hygienic, and environment-friendly alternative.
A commercial compost facility optimises the process to ensure rapid biodegradation of organic material. Commercial composting methods consist of chippers, grinders, and mixers.
These pieces of equipment assure that all items reach ideal composting conditions. Organics are screened beforehand, and large items or non-organics are removed.
The leftover bits are thus more manageable for the microbes to break down naturally.
Commercial compost facilities can monitor and control temperature, moisture, and airflow to encourage bacterial activity. The heat involved kills dangerous bacteria as well.
In a commercial composting bin, the following can be composed:
- Raw mussel shells
- Chicken bones
- Dairy products
- Cooked food
- Produce stickers
- Glossy or coated paper
- Treated wood
- Fast-growing weeds or plants
- Certain types of plant waste (black walnut leaves)
- Coal and coal ash
- Diseased or infested plants
- Any plant matter that has been treated with chemicals
- Along with everything from home composting
At home compost pile, the following can be composed:
- Paper towels
- Paper bags
- Q-tips (with no plastic)
- Seafood shells
As landfill spaces decrease, there will surely be more demand for composting organic waste.
Additionally, as tipping fee increases and it grows to be costly to landfill the wastes, composting may turn out to be an engaging economic alternative as well as a value-added opportunity.
US states like Oregon and Washington are encouraging laws that will require all businesses to compost their organic waste, including food waste. As agricultural practices proceed to weaken soils and deplete organic matter, compost will maintain soil fertility.
Compost also plays a vital role in more environmentally controlled and aware agricultural systems.
For many livestock, poultry, and sustainable and alternative agriculture operations, compost and composting may be the best choice and the opportunity for added income.