In this article we will discuss about:- 1. Introduction to Compositing 2. History of Composting 3. Types of Compost and Their Benefits 4. Role of Microbes 5. Vermicomposting.
- Introduction to Compositing
- History of Composting
- Types of Compost and Their Benefits
- Role of Microbes in Composting
1. Introduction to Compositing:
Using organic waste in agriculture has manifold relevance to today’s rural and urban environment. It is extremely useful for organic farming and is also an important technology for solid waste management. The use of organic waste materials in agriculture is not new. From centuries of experience farmers are composting organic matter for obtaining fertilizers.
Compost is organic matter that is decomposed and recycled as a fertilizer. It is a green technology which converts organic waste into useful fertilizers. Compost is a key ingredient of organic farming.
Compost is the end product of a number of biological degradation processes of organic material, which can vary from dead leaves to kitchen waste and agricultural residue. When the organic waste material is well decomposed, the odorless and pathogen free black -brown mixture can be used to enrich the soil. Good compost resembles humus that is made naturally in the soil from plant and animal residues.
When waste is not managed properly, it can cause serious health and environmental risks. The overall goal of municipal waste management is to improve and safeguard public health and reduce waste.
2. History of Composting:
The Egyptians were one of the first civilizations to recognize the role of earthworms in soil. Under Cleopatra’s rule, the removal of earthworms from Egypt was considered a crime. Scholars such as Aristotle and Charles Darwin advocated the role of earthworms in decomposing organic matter into rich humus. Earthworms are often referred to as ecosystem engineers.
In 1940, Sir Albert Howard developed a composting method by mixing three parts of green matter such as plant leaves, to one part of brown matter, such as animal manure.
Howard believed that compost was a natural way of producing plant fertilizer and which provided a good source of nutrients to plants.
3. Types of Compost and Their Benefits:
Composting is the natural breakdown of organic matter to produce a crumbly nutrient-rich soil. It is a naturally occurring process of decomposition found in nature, which takes several months to a year approximately. Human beings speed up this natural process by different composting methods. Modern methods of composting are a multi-step, closely monitored process with measured inputs of raw materials.
Composts can be made from the following:
i. Food waste.
ii. Leaves and garden waste.
iii. Crop residue.
iv. Farm Yard Manure (FYM) of cow, horse, sheep or poultry.
v. Mushroom compost.
In India the above wastes are regularly generated in large quantities from domestic garbage, garden, industry and the agriculture sector. Crop residues are the bulk of organic waste that is generated as part of agricultural activity. Three quarters of total crop residues in India are produced by three crops viz. rice, wheat and oilseeds.
Composting technology has been recognized as an eco-friendly and cost effective method to convert wastes of plant and animal origin into a product that nourishes plants.
Composting offers several other benefits such as enhanced soil fertility and soil health, thereby increasing agricultural productivity and improved soil biodiversity.
Composting is a popular method of waste disposal as it is a low cost and low infrastructure set-up and also produces valuable compost. United Nations Environment Program (UNEP) defines composting as “the biological decomposition of biodegradable solid waste under predominantly aerobic conditions to a state that is sufficiently stable for nuisance-free storage and handling and is satisfactorily matured for safe use in agriculture”.
Composting is a decomposition process in which the organic matter is progressively broken down by a succession of populations of living organisms. The breakdown products of one population serve as the substrate for the succeeding population.
Composting of organic waste is undertaken by the following methods:
(a) Windrow Composting:
It is the most common method of composting in India; it involves the stabilization of organic solid waste through aerobic decomposition. It can efficiently handle large quantities of waste.
(b) Mechanical Biological Treatment Plants (MBT):
They use mechanical and biological operations to handle mixed waste.
It is a composting method using earthworms.
4. Role of Microbes in Composting:
The composting process is dependent on micro-organisms to break down organic matter into compost. There are many types of micro-organisms found in the compost pile, out of which the most common are bacteria, actinomycetes, fungi and protozoa. The most numerous of all the microorganisms found in compost are bacteria.
Composting is a microbiological process which progresses from the mesophilic stage (20-40°C) to the thermophilic stage (above 40°C) and then passing to gradual cool stable stage. Mesophilic bacteria initiate the decomposition of organic substances such as proteins, sugars and starch.
The heat produced during microbial ‘metabolism raises the internal temperature. As the temperature rises above 40°C, the mesophilic micro-organisms become less and are replaced by thermophilic microbes. At high temperatures, many pathogens and weeds are destroyed.
Aeration, watering or turning of the compost pile prevents excessive heating. For normal functioning of microbes, wet the pile frequently so that moisture content is above 40%.Bacteria require oxygen to function therefore aerobic conditions should be there in the compost pit.
The microbial populations during the thermophilic phase are dominated by members of the genus Bacillus and Actinomycetes. During composting Actinomycetes play an important role in degrading complex compounds such as cellulose, lignin, chitin, and proteins? In compost, fungi are also important, because they break down cellulose and lignin, enabling bacteria to continue the decomposition process of simpler compounds.
Fungi are numerous during both mesophilic and thermophilic phases of composting. At the highest compost temperatures, bacteria of the genus Thermus are active and breakdown complex organic compounds.
These organisms are known as biogeochemical agents as they change the chemistry of biological waste and release useful chemicals. The organic matter is finally converted into carbon dioxide, ammonium and nutrients. Ammonium is the form of nitrogen used by plants. When available ammonium is not used by plants, it is further converted by bacteria into nitrates through the process of nitrification.
Compost is also rich in macronutrients such as NPK (Nitrogen, Phosphorus and Potassium) and several micronutrients.
The higher the content of NPK nutrients, the greater the fertilizer value of the compost. The NPK values for compost depends on the type and the initial C/N ratio of the organic waste used.
Organic chemicals such as pesticides and polychlorinated bi-phenyls and heavy metals should not be present in the waste as they make compost undesirable for land application.
Vermicomposting in recent years has gained importance because of its higher economic value over traditional methods of composting. Vermicomposting was originally developed to remove unwanted organic materials from the agricultural and industrial wastes. Worms are an integral part of this composting system.
Vermicomposting is also known as vermiculture. It is faster than other forms of composting and resulting earthworm castings are rich in microbial activity and plant growth regulators. It is the process of turning organic debris into worm castings. These worm castings are very important for the fertility of the soil. Earthworms through a type of biological alchemy, are capable of transforming garbage into gold.
Types of Earthworms:
Earthworms are found throughout the world. These invertebrates are small (10-300mm long) tube shaped organisms that live in or on top of the soil. Worms start their life as a cocoon deposited in the soil by adult worms. Worms can live from a few months to 10 years, but they usually do not reach the latter age because of the environmental hazards to which they are exposed.
Worms have a relatively simple digestive system that runs along the length of their body. Organic matter is ingested from the mouth and is then passed through a gizzard where strong muscles contract and grind up the organic matter. Enzymes are then released by the stomach to break down organic matter and release energy that the worm can use.
Worms have a symbiotic relationship with microorganisms in their digestive system. The microorganisms help the worm digest organic matter while the worm gives the microorganisms a place to live. In turn, both the microorganisms and the worm benefit from this relationship. Vermicasts are the organic material that has passed through the earthworm’s digestive system and is excreted.
Vermicasts contain more micro-organisms, inorganic materials, and organic matter than that present in regular soil. There are approximately 4,400 different species of earthworms which have been identified worldwide.
They are mainly divided into two types, Burrowing and Non-burrowing:
a. The burrowing types such as Pertima elongate and Pertima asitica live deep in the soil.
b. They are pale, 20 to 30 cm long and live for 15 years.
c. These type of earthworms come up to the soil surface only at night.
b. They make holes in the soil up to a depth of 3.5m and produce a large amount of casts by ingesting 90% soil and 10% organic waste.
a. The non-burrowing earthworm Eisenia foetida and Eudrilus eugeniae live in the upper layer of soil surface.
b. They are red or purple in color and 10 to 15cm long. Their life span is only 28 months.
c. These earthworms eat 10% soil and 90% organic waste materials.
d. They convert the organic waste into vermicompost faster than the burrowing earthworms.
e. They can tolerate temperatures ranging from 0 to 40°C and 40-60% moisture level in the pile.
The species of earthworm used most often to produce vermicompost are –
(i) Red wiggler (Eiseniafoetida)
(ii) Lumbricus rubellus
(iii)European night crawler (Eisenia kortensis)
Eisenia foetida has a fast rate of decomposition that is why it is usually chosen as the worm for vermiculture, it reduces the time needed to make compost. Also, it consumes more organic matter and less soil.
Role of Earthworms:
The earthworms perform different roles in the soil such as that of a Turner, Mixer, Aerator and Accelerator.
Earthworms take nutrients down through the soil profile, bringing them into closer contact with plant roots.
Earthworms are also responsible for mixing soil layers and incorporating organic matter into the soil. Charles Darwin referred to earthworms as ‘nature’s ploughs’ because of this mixing of soil and organic matter. This improves the fertility of the soil by allowing the organic matter to be dispersed through the soil and the nutrients held in it to become available to bacteria, fungi and plants.
Earthworms improve soil aeration. Their movement in the soil creates channels which improve soil aeration. These burrows create pores through which oxygen and water can enter and carbon dioxide can leave the soil. Also, earthworm casts cement soil particles together, make the soil well aggregated, improve soil porosity and thereby improve the soil aeration.
Earthworms play an important role in accelerating the process of decomposition. Earthworms do this by eating organic matter and breaking it down into smaller pieces allowing bacteria and fungi to feed on it to release the nutrients.
Earthworms consume various organic wastes and reduce the volume by 40-50%. Each earthworm’s weight is about 0.5 to 0.6 gm, eats waste equivalent to its body weight and produces cast equivalent to about 50% of the waste it consumes in day .The worm casting contains a high percentage of both macro and micro nutrients. The C/N ratio of the soil is also improved by the activity of earthworms.
A study conducted by Delhi University students revealed that there is a drastic change in organic matter and nutrient content in the beginning and end of the vermicompost process. The organic matter is reduced at the time of harvest of vermicompost whereas the nitrate produced on decomposition is high in ready compost.
Requirements for Earthworm:
Earthworms are very sensitive organisms and only grow and multiply when the environment is optimum. They are usually found where there is enough organic matter and disappear when organic matter is in short supply. Earthworms are sensitive to pH and prefer neutral pH. It is therefore not advisable to put tomatoes and citric food items in the compost pile.
Earthworms can be killed by extreme temperature; they function normally between 10 to 40 degrees Celsius. Earthworms need moisture for survival and die in dry conditions. As they lose 20 percent of their body weight each day in mucus and castings, they need moisture to stay alive. They need 40 percent water and when the pit is water logged they are not comfortable and move out. The vermicompost pit should be in a shady cool place.