**3. Types of agricultural waste**

There are three major types of agricultural waste (**Figure 2**):


**Figure 2.** *Types of agricultural waste.*

3.**Agro-industrial residues**: These are in the category of secondary agricultural residuals produced after processing of agricultural crop into various bioproduct forms. These include husk, molasses, bagasse, peels, hulls, husk, etc.

iv. Phase IV: Methonogenesis

*Role of Decomposers in Agricultural Waste Management DOI: http://dx.doi.org/10.5772/intechopen.93816*

v. Phase V: Humification

archea and the bacteria [18].

and other organic constituents [21].

t = time interval (days)

**529**

a. Hydrolysis

carrying out by the interaction of various microbes [19].

compounds.

phase is the longest phase of decomposition.

The organic acids products, viz., acetic, propionic, and butyric acids are converted into CH4 and CO2 as intermediate products by methoanogenic microorganisms. In this phase, pH changes from acidic to neutral. This

All the microbial activity slows down in this phase and CH4 production also completely disappears. All the remaining organic materials are converted into gas phase by the oxidative processes and converted into humic acid

2.**Anaerobic decomposition:** Anaerobic decomposition is gaining attention in various energy sources to fulfill the demand of increasing population in a safer

and economical way [17]. There are around 267 plants that have been distributed all over the world. In anaerobic decomposition, microorganisms decompose the solid waste into biodegradable and nontoxic forms in the absence of oxygen (1). There are two types of bacteria which play a significant role in anaerobic decomposition reactions, which include hydrolytic bacteria and the acidogenic bacteria. These two bacteria belong to two kingdoms, the

There are four successive stages of anaerobic decomposition which are: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. These four stages are

The decomposition pathways start with the hydrolysis of the waste agricultural biomass, which is rich in complex polymeric constituents. The hydrolytical cleavage broke the polymeric interconnecting bonds by the hydrolysis process. Agricultural waste is rich in organic polymers such as cellulose, hemicelluloses, lignin, etc. [20]. Hydrolysis breakdown is an electrochemical process driven by the hydrolytic bacteria by cellulolytic enzymes, lipase enzymes, etc. Hydrolysis cleavage converts these insoluble long chain polymers into soluble simpler derivatives like ammonium

Kinetically, hydrolysis reactions are the first-order reactions in which complex biodegradable waste material is hydrolyzed at constant temperature and pH [22].

ð Þ C6H10O5 n þ n H2O ! n C6H12O6 þ n H2

Hydrolysis reactions in anaerobic decomposition can be considered as ratedetermining steps, which depend upon the ration of hydrolytic product to microorganisms, pH 5–7, and 30–35°C [23]. The hydrolysis reactions make the agricultural postharvesting biodegradable waste residue into e simpler forms and make it

dt ¼ �*Kh:*Xdegr (1)

)

dXdegr

where Xdegr = Amt. of Decomposed material (kg/m<sup>3</sup>

kh = hydrolysis constant in first order reaction.

accessible for acidogenic bacteria for further breakup.
