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8 Microbes and their Consortia as Essential Additives for the Composting of Solid Waste

Thermoactinomycetes, Aspergillus sp., white-rot fungi, Trichoderma sp., etc. [14].

These microbial additives will deal with the organic portion of the waste by secret-

ing degradative–oxidative enzymes. The enzymes will shorten the initial lag time

and generate a phenomenal rise in temperature that justify the accelerated rate of

waste composting. However, not all the microbial strains have the ability to secrete

enzymes, good enough for solid waste biodegradation. They significantly affect the

physical, chemical as well as biological parameters (pH, C/N ratio, color, humic

substances, pathogenic activity, and germination index) within the waste matrix

which are indirectly related to the compost quality. Monitoring the temperature,

ammonia emissions, C/N ratio, etc., can effectively present a clear picture about the

quality of the generated compost [8]. In addition, reduction in composting time,

C/N ratio, and organic content will clearly indicate good enriched compost. Some

investigations discussing the impact of microbial addition on the degradation of

various solid wastes (MSW, FW, and AW) have been summarized in Table 8.1.

8.4

Effect of Microbial Consortia on Solid Waste

Composting

While exploring the synergistic action of potent microbes in a consortium on com-

posting of solid waste, a boost in the waste degradation rate and reduction in the

composting time was evident. To support this, a MSW composting experiment was

performed, where feedstock material was inoculated with a mixed microbial culture

of Phanerochaete chrysosporium, Trichoderma viride, and Pseudomonas aeruginosa.

Here, decrease in the composting period was observed [14]. In another investigation

on passive bin composting of MSW, an inoculum of Bacillus subtilis, Bacillus amy-

loliquefaciens, Bacillus nakamurai, and Bacillus velezensis was added. Here, rapid

degradation of organic substrates was confirmed with maximum humification

[35, 36]. A study recorded enhanced mineralization rate when MSW was

co-composted using mixed cultures of bacteria and fungi (Bacillus Casei, Can-

dida rugopelliculosa, Lactobacillus buchneri, and white-rot fungi Trichoderma)

[37]. Following the same approach, transformations in carbon content and C/N

ratio were brought in MSW composting due to the addition of fungal consortium

[38]. Among three aerated composting bioreactors having Aspergillus niger or old

compost or control as additive, maximum decrease in C/N ratio was observed in the

first one (63.37% or 59.6% or 46%, respectively). Operation time was also reduced

in the first case (18 days). Checking the effect of potent microbial consortium

(8% inoculum) on waste mineralization represented a stable pH, C/N ratio (30),

temperature (27 ^∘C), and carbon dioxide formation (5.28 d/l) [18].

Experimental conditions were modified and an extreme rise in the waste degra-

dation rate was noticed, when microbial additives were inoculated at multiple

stages (initial and second stage) of MSW composting [19]. This can be attributed

to improved microbial diversity and lesser competition between additives and

indigenous microbes [22] with repressed foul odor and better polymerization or

humification of waste. Inoculation of fungal consortia during MSW composting