Dimensions of particles influence the rate of organic matter breakdown. The quantity of the particle’s mass exposed to the microbe’s attack is determined fr om the ratio of mass to the surface area. Greater the surface area accessible to the microbe, the less difficult it is for microbes to show their activity. This is because the major task is carried at the boundary between the particle surface and air. Microbes are capable of digesting more, produce a large amount of heat, and reproduce more rapidly with a small amount of substance. Besides, smaller pieces speed up the process of breakdown of organic material. These materials can be tom, cut, beaten, or even perforated to amplify their surface area. Various methods are utilized for these purposes. For example, a lawn trimmer is utilized to chop leaves in a garbage container. Various types of shredders and drippers are accessible in the market for shredding woody materials and foliage. However, safety goggles should be for grating and chopping purposes. Hands must be taken care off while the machine is working. Kitchen leftovers can be cut with the aid of a table knife. Some determined citizens utilize meat grinders to make “garbage soup” from the leftovers of foodstuff and then pour the blend or mixture into their garbage heaps.
The most important environmental factors that influence the rate and degree of decomposition in composting are temperature, pH, moisture, nutritious food, and aeration. Deficiency in any of these aspects slows down the composting process. Thus, the scarce factor becomes the rate-limiting factor.
The temperature within the compost heap acts as an important factor in the maintenance of microbial growth and activity. Consequently, temperature also affects the rate at which the raw materials decay. Higher temperatures result in a quicker breakdown of organic matter. However, exceptionally high temperatures can slow up the activity of microbes. Composting is most advantageous when the temperature of the composting substance is within the two ranges, i.e., Mesophilic (80-120°F) or Thermophilic (105-150°F). Mesophilic temperatures permit successful composting, but most experts advise maintaining temperatures between 110 and 150°F for composting. The process of composting is influenced at temperatures higher than 65°C. This is on account of the reason that microbes associated with the sporeforming phase, form spores above 65°C. Other microbes either nimble into the resting stage or get killed. An alternate way is to resort to those measures which are premeditated to evade temperatures greater than 60°C.
The growth of microbes is also influenced by the alkalinity or acidity of the waste material. The pH values of 6.0-7.5 are preferred by bacteria for decomposition, whereas fungi prefer pH ranging from 5.5 to 8.0. However, gaseous losses like that of ammonia take place if pH exceeds 7.5. There are few materials like wastes from the paper industry, cement factories, and daily farms, which can enhance pH values. The initial pH levels do not cause hindrance to most of the microbes. Therefore, there is no need of buffering in the initial stages. In fact, it may have an unfavorable result in microbial gr owth. Nonetheless, the addition of lime proves beneficial in a few cases. It enhances the physical features of the compost, possibly by absorbing moisture.
The preferable moisture values of the compost mass range between 45-60% by weight. Low moisture content will hamper the process of composting, as it will divest microbes of water required for their metabolism. This, hi turn, will inhibit the activity of the microbes. Extreme desiccation makes piles prone to unprompted combustion (Fernandes and Sartaj, 1997). However, if the compost mass is highly hydrated, it may block the pile’s air spaces, creating an anaerobic situation. Many compounds need anaerobic conditions for their breakdown, like halogenated hydrocarbons. There are various methods, which can be utilized to measure anaerobic conditions. Manure and composting test laboratories are there to evaluate moisture content. Moisture can be evaluated by manure and compost-testing laboratory. Besides, moisture meters are also available in the market. Nonetheless, a more realistic and simple approach is the ‘squeeze test.’ In this test, the mixture is pressed in a gloved hand. If more than a small number of drops of water come out, it means the sample is too much drenched. If it appears to be very dehydrated, more moisture needs to be incorporated. The degree of dampness of compost mass depends on the organic waste’s organization. Leaves require less moisture content when compared with wheat or com stalks. Similarly, food leftovers or grass cuttings need less moisture content. If a compost pile is dried up, it should be hydrated immediately. Few substances like straw, dead leaves, and hay are slowly moistened till they get glistened. Such substances have a propensity to discard or adsorb water only on their exterior surface. It should be noted that if the pile gets saturated with water, it should be turned and restacked.
Composting can take place under both anaerobic and aerobic situations. Nevertheless, aerobic composting is proficient than anaerobic. Even though the air contains 21% oxygen, aerobic microorganisms can thrive even at 02 concentrations of 5%. However, the O, concentrations of more than 10% are considered as most advantageous in the composting process. The organization of the constituents of the waste decides the degree of aeration. Besides, the techniques used for aeration also govern the amount of aeration required under aerobic conditions. Aeration is essential for successfiil composting. It can be either active or passive. With an increase in microbial activity, more, and more O, utilized. If the O, supply is not properly replenished, the process of composting may shift to an anaerobic state. This will, in turn, slow down the composting process. Good aeration enhances aerobic composting. If the heaps are too large, soaked, or have less porosity, aerobic bacteria cannot get adequate O,, and anaerobic bacteria take charge. However, a stinking smell may be generated in such processes. Few by-products of anaerobic respiration like sulfur compounds are well known for this. The odors’ types and intensities depend on the type of feedstock and operating circumstances required in the composting process. Since these odors create a lot of annoyance to the people, therefore it is necessary to control them. Such problems may arise, especially in the regions where the composting process is carried out near a human population. Various methods are used to deal with the stinking smell arising out of composting. One of the most widely used methods is bio-filtration. This is an efficient method to lessen the intensity of odors produced due to the dispensation of organic matter.
During composting, microbes break down the complex organic material into simpler forms to obtain energy. This energy is utilized to cany out various life processes and acquire nutrients to continue their populations. Among all the substances needed for microbial decomposition, C and N are the most significant. Carbon acts as a source of energy and growth for microbial cells. Nitrogen is a vital constituent of enzymes, proteins, nucleic acids, coenzymes, etc., that is necessary for cell development and function.
Many microbes have been shown to be linked with composts. It is obvious that the microbial community, as a whole, plays a vital role in the decomposition of organic materials. Bacteria (especially mesophiles and thennophiles) and other microbes like fungi are the chief living organisms involved in composting’s preliminary active phases. Mostly, minute forms like rotifers, amoeba a few protozoans are foremost to come into sight at the composting site. Ultimately, bigger forms like snails and earthworms (Eisenia foetida and Lumbricus terestris) become abundant. The compost mass gets reasonably matured once the earthworms come into play. The usage of earthworms in the process of composting has led to the emergence of vermicomposting. Bigger organisms take part in the physical transformation of organic matter into compost. However, they are vigorous in the later stages of composting, like in chopping, chewing, mixing, and digesting of compostable mass. Thus, they break larger particles into smaller pieces, and transform them into a more digestible state for microbes.
RAPID COMPOSTING METHODS
The composting process takes a lot of time, which may range from 100-180 days. Substantial research has, therefore, been carried out to speed up the process of composting, by the introduction of suitable microbes with good proficiency in decomposing of organic matter. Presently, the compost producers use microbial inoculants for the quick decomposition of biodegradable material and repression of foul odor. The government institutes like the Indian Agricultural Research Institute and Indian Institute of Soil Science, have formulated efficient cultures which are being utilized by the compost producers. Some processes through which compost production can be enhanced are described below:
hi this method, suitable minerals, fertilizers, and microbial cultures are used to fortify the compost so that the end product contains more nutrients per unit volume or weight. It also makes use of compost accelerating culture and biofertilizers for further nutrient enrichment. This reduces the bulk, which has to be transported.