# Dairy Waste and Potential of Small-Scale Biogas Digester for Rural Energy in India
## 5 Limitation in Biogas Production and Future Biogas Potential in India  
While biogas technology is a robust and well-proven technique for converting animal waste into biogas, multiple challenges exist in India for large scale adaptations. Both technical and non-technological barriers exist [41], which hinders the dissemination of biogas technology in India. One of the major barriers is economic in rural areas. Biogas technology adaptations in urban areas are limited because, previously, the majority of livestock populations were in rural areas. However, currently a large number of small to medium size dairy industries, which house 10-100 dairy cows, are located in the vicinity of urban areas, where biogas digesters can play crucial role in treating animal waste, removing odor problems, creating a better environment for livestock, and converting livestock waste into biogas, a source of renewable energy. Here, it is important to clarify the definition of rural versus urban areas in the context of India because the definition of rural and urban areas differ from one country to the next. In India, rural areas are defined (based on national sample survey organizations) as the living environment where the population density is up to 400 per square kilometer. On the other hand, urban areas are defined cities with a population of more than 5000. An additional criteria for urban areas is that 75% of male workforce in the city should be engaged in non-agriculture activities. In urban areas, the availability of livestock waste could be low, however, combining the food waste (often available abundantly) with livestock to operate these digesters can also improve the biogas production as it can enhance the food waste recycling and control the excessive influx of food waste into landfills. Currently, livestock living environments and sanitation in livestock housing requires improvement in many dairy farms in India. A new National Biogas and Organic Manure Program (NNBOMP) has been launched to promote the installation of biogas plants of sizes between 1 and 25 m\({}^{3}\) with the objective of providing green and clean renewable energy source for domestic purposes [61, 62]. Considering the livestock population in India, a substantial potential exists for producing biogas and organic fertilizer generated by biogas plants. An estimation showed that around 302.23 million livestock heads can produce 33,000 million m\({}^{3}\) biogas considering collection recovery of cattle dung of 70%. Recently, multiple biogas-based projects with the aim of producing power have been installed, with power generation capacities of 212 kW and a corresponding biogas generation capacity of 1805 m\({}^{3}\)/day, which can be seen as positive development in terms of biogas technology adaptions. Recently waste-to-energy projects are commissioned, and existing capacity is to produce biogas of 702,508 m\({}^{3}\) per day and 84,759 kg per day of compressed biogas, and 141 MW of biogas-based electric power per day [62, 63]. Currently, the cumulative total of 316 biogas-based projects are in operation with a total power generation capacity of 7.166 MW, however, considering the potential of biogas productions existing capacity is substantially low [55, 56, 57]. Relatively, the cost of constructions of biogas plants in India vary between $102 USD to $479 for 1 m\({}^{3}\) to 25 m\({}^{3}\), respectively, which is an affordable investment considering the benefits of biogas plants [63]. Large-scale biogas plants (\(>\)5000 m\({}^{3}\)), which can use livestock waste and other organic waste including municipal waste can be used for converting organic waste into renewable energy is yet to be explored in India at large scale [41]. The use of biogas for transportation requires additional processes such as scrubbing, compression and upgradation of biogas, which can replace existing fossil-based transport fuel is yet to be achieved [42, 43].