What are the roles of microbes in the environmental protection

Under natural conditions dead vegetable and animal materials decompose under the influence of bacteria and fungi, wherever they fall and add to the fertility of the soil. In many places farmers have to depend on organic manure derived from animal excreta, agricultural wastes and vegetation.

Kitchen wastes and garden wastes in domestic solid wastes are of biodegradable nature. Urban areas generate domestic and commercial wastes on large scale around 300 to 800 gms/person/day.

A city with a population to 1 million may generate almost 500 tonnes per day. Between 25-75 percent of this may be vegetable and purtrescible matter. Composting is biological process. Just as the microorganisms in water take up biodegradable organic matter as their food.

Similarly microorganisms in soil also use biodegradable organic matter as food. This process can be either aerobic or anaerobic. Composting has three products; compost as an organic fertilizer salvaged materials for resale and non-compostable as land fill materials. The aim of composting is to convert a major portion of solid wastes into marketable product.

Composting needs proper control to make the process proceed without production of odors propagation of insects, destroy pathogens present in the original wastes, destroy weed seeds, retain maximum nutrient content of NP and K minimize time required to complete the process and minimize the land requirement required for the process.

There are two main groups of bacteria i.e. anaerobic bacteria which function in the absence of oxygen and aerobic bacteria which require oxygen. There are also some facultative organisms that can adapt to either of environment.

The important features of anaerobic composting are:

(i) It is a lengthy process extending over a period of 4-12 months.

(ii) It is a low temperature process and the destruction of pathogens is accomplished by their exposure to an unfavorable environment for long periods.

(iii) The gaseous products of reduction are methane, hydrogen sulfide and other gases with offensive odors.

Anaerobic composting is practiced in Indian villages on a small scale for combined disposal of solid wastes and night soil the materials are placed in alternate layers in small trenches which are sealed and left undisturbed for many months, the contents are the dugout and used as compost. This is called the Bangalore System being abandoned in favour of cheaper aerobic method.

Aerobic composting is characterized by rapid decomposition, high temperatures are attained which achieve speedy destruction of pathogens, insect eggs and weed seeds, no offensive smells will be there if proper aerobic system is maintained. Aerobic system is also called Indore system, Many types of organisms assist in the decomposition, bacteria which predominate at all stages, fungi attacking cellulosic materials and actinomycetes during the final stage/The process begins at ambient temperature by the activity of mesophilic bacteria which oxidize carbon to carbon dioxide, liberating large amounts of heat. Usually the temperatures go beyond 45°C within two days.

At this point the mesophils cannot continue and the thermophilic bacterial stage starts which lasts about two weeks taking the temperature to 55° C to 70°C. The process is dependent on availability of air and moisture.

Moisture content is critical factor and it should be maintained above 40% always. If it exceeds beyond 55-60 percent then air spaces between solid particles may get clogged reducing oxygen availability. So control of moisture is critical. The initial C/N ratio is important. The range may be 20: 1 to 70 : 1 initially, which gets reduced to less than 15 :

A modified method of composting using earth worms has gained importance. Pune can be termed as the composting capital of India. People from all walks of life are involved in solid waste management (SWM) work.

It is in Pune that the importance of rag pickers was realized. An earthworm expert Sri Uday Bhawalkar started experiments with solid waste management in his house.

Another lady Ms. Lata Shlkhande experimented on her terrace garden by making a lace for garbage treatment by filling that area with ‘ garbage. She sprinkled earthworm culture (cocoons of worms).

The worms nibbled away the organic matter and at the end of the week the material became compost. Having seven sites at hand, everyday one site can be filled for use. The worms also multiply and are used in subsequent heaps. This activity has taken a lead to have larger vermiculture composting.