# Dairy Waste and Potential of Small-Scale Biogas Digester for Rural Energy in India
## 4 Biogas Promotion and Various Biogas Model Types Population in India  
In India, the substantial uses of biogas energy and installations of biogas plants started in 1981-1982, when a National Project on Biogas Development (NPBD) was launched by the Ministry of Non-Conventional Energy Sources (MNES) [55; 56]. Under this program, the installation of small-size biogas plants, which can be operated using 2-4 livestock were popularized. Substantial portions of expenditures incurred during installations of these plants were covered by the MNES [55]. The NPBD projects incentivized households to accept biogas technology, workers help in construction, and implementing agencies support the dissemination of biogas technologies in India. This was a crucial initiative by MNES since fossil fuel-based energy sources such as liquid petroleum gas were not commonly available in rural areas of India [57; 58]. The nation-wide implementation of NPBD project helped in the installation of biogas plants across India. The top five provinces, which have the largest number of small size biogas plants are Maharashtra, Kamataka, Uttar Pradesh, Gujarat, Madhya Pradesh. Biogas plant numbers and livestock populations in these provinces are shown in Table 3. The largest number of biogas plants (about a million) are installed in various rural parts of Maharashtra. In Madhya Pradesh, the number of biogas plants are approximately 376,221 [58; 59; 60]. In India, multiple types of small-scale biogas digesters have been promoted. These can be divided into two major types: (1) floating type biogas plants; and (2) fixed dome types. Both floating and fixed dome types of biogas plants are semicontinuous types (Figure 4). A typical floating drum type biogas plant (Figure 5) involves a floating chamber, a manure chamber, feed inlet, and effluent outlets. In fixed dome-type biogas plants, a chamber/head space, which holds biogas, is fixed type (Figure 6). These fixed dome-type biogas plants also involve feed inlet, effluent outlets, and a chamber to house manure in anaerobic environment. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**State/Province** & **Biogas Plant** & **Livestock Number** & **Sources** \\
**Names** & **Number** & **(Million)** & **Sources** \\ \hline Maharashtra & 924,092 & 33 & \\ Karnataka & 510,942 & 29 & \\ Uttar Pradesh & 440,949 & 67.8 & [37; 55; 59; 60] \\ Gujarat & 435,287 & 26.9 & \\ Madhya Pradesh & 376,221 & 40.6 & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Top five provinces with largest number of biogas plants in India. Figure 4: Classification of various types of biogas plants in India. Figure 5: Floating dome types of biogas plants in India. Figure 5 shows a typical floating drum type biogas plant, which can vary in size between 1-10 m\({}^{3}\). This is also known as KVIC type. There are 4 different types of floating drum-based biogas plants (Figure 3): (1) KVIC; (2) Pragati; (3) Ganesh; and (4) ferro cement floating drum. A biogas collector, which is under floating conditions and collects the gas; depending on the biogas volume and pressure, it moves upwards and downwards, which regulates biogas pressure at the biogas outlets (Figure 4). In general, floating drum is built of metals, and concrete is used to build chamber for housing livestock waste under anaerobic conditions. Fixed dome biogas plant design is shown in Figure 6. In contrast to the floating drum, in the fixed dome gas the chamber/head space is fixed and an outlet is provided in the top of fixed dome for gas. The anaerobic chamber, which houses livestock waste in anaerobic conditions, is built using concrete. Inlet and outlets of fixed dome and floating drone are similar in nature. While comparing the efficiency of the fixed dome and floating dome biogas plants, studies showed that gas losses are higher in a floating dome type of digester, particularly when biogas was used to run a diesel engine. Fixed dome type of biogas plants has lower biogas losses.