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8 Microbes and their Consortia as Essential Additives for the Composting of Solid Waste
eventually moderate the harmful impact of SW on environment and human health.
The solid waste mainly constitutes of heterogeneous as well as homogeneous wastes
discarded from residential, industrial, and agricultural areas. It may be categorized
in the following three ways:
●On the basis of source of origin: municipal solid waste (MSW), agro waste (AW),
industrial waste, bio-medical, e-waste)
●On the basis of nature of waste: organic and inorganic material
●On the basis of toxicity: hazardous and non-hazardous
The MSW comprises of food waste (FW), rubbish from residences, commercial,
institutional, industrial, construction, demolition, and sanitation waste. It also
includes recyclables like paper (3–6%), plastic, glass, and metal (each less than 1%);
toxic substances such as paints, pesticides, used batteries, and unused medicines.
The organic and inorganic fractions encompass kitchen refuse, packaging material,
fruit and vegetable waste, clothes, used bottles, paper, cans, batteries, etc., which
generally do not carry any value to the primary user [3, 4].
The monitoring and management of solid waste is a grave concern for developed as
well as developing economies, posing a bigger challenge for municipal authorities.
Further, various processes and techniques that are employed for effective manage-
ment of such waste must include monitoring, gathering, transportation, processing,
recycling/recovery, and appropriate discarding of final residue.
8.3
Role of Microbes in Composting
Composting is considered as a significant approach for treatment and disposal of
solid wastes, but with a question of time and efforts required toward processing and
degradation. The solution to this lies with the organic composition of the waste as
they possess enormous amount of cellulose, hemicellulose, sugar components, and
lignin. Composting refers to biological hydrolysis of solid waste (organic fraction)
into a stable and sanitized residue called humus [5]. It is an aerobic process wherein
microbes implicate the waste decomposition by consuming carbon and nitrogen as
energy sources. A sufficient percentage of oxygen (15–20%) and water is directly cor-
related with an efficacious microbial succession [6]. This is essentially required to
ensure a spontaneous rise in temperature to eliminate the pathogens, ultimately gen-
erating a good product in the form of soil-enriching compost.
The process of composting can be divided in to three phases: (i) an initial
mesophilic phase, where mesophilic bacteria and fungi degrade the simpler
compounds such as sugars, amino acids, etc., at a temperature of around 45 ∘C;
(ii) thermophilic phase, where thermophilic bacteria and fungi degrade complex
compounds like fats, cellulose, hemicellulose, and lignin at a temperature of around
60 ∘C; and (iii) cooling phase materializes products (humic-like substances) with
limited microbial activity, decreased temperature, and a declined organic matter
degradation. A gradual and effectual microbial succession is critical for composting
wherein growth of nonspecific microbes extensively affects the waste degradation