In order to reduce emissions of greenhouse gases, related global warming and dependency on fossil fuels, it is crucial to promote the uses of renewable energy, and conversion of biomass and organic waste into energy sources. In many parts of the world, a substantial increase in efforts for the conversion of waste into energy is currently being observed. Specifically, biogas technology has been emphasized for the conversion of animal waste into biomethane/biogas because livestock waste is considered to be a substantial source of ambient greenhouse gases, causing climate change. While biogas technology, an anerobic process to convert livestock waste into biogas, is promoted in both developed and developing countries, this review article is focused on improving our existing understanding of small-scale biogas technology and relevance of this technology in rural environment of India. A thorough review research has been performed to gather the information on livestock population, manure production, and potential of biogas technology in India to provide a wholistic information. A summary of the financial supports facilitated by various agencies, the cost of biogas plants, potential uses, and potential challenges in the dissemination of biogas technology in India has been discussed in this study. We anticipate that the data and interpretation provided here will help in understanding the scope of biogas technology in India and will help in formulating the policies which will support the implementation of biogas technologies in developing countries.

Liquid dairy manure, which is produced in enormous quantities in flush dairy manure management systems, is commonly used as an alternative to chemical fertilizers. It provides nutrient benefits to crops and soils. While dairy waste is a well-accepted and widely used fertilizer, the presence of indicator organisms and human pathogens in manure may lead to pathogen contamination in crops and soils. This study is focused on the examination of ozone gas-based sterilization. In the past, ozone (O3) has been used for sanitizing various foods and solid surfaces, but the potential of O3 for eliminating human pathogens in liquid dairy waste is not studied yet. Pathogens such as Salmonella Typhimurium and Escherichia coli O157:H7 are reported to be present in liquid dairy manure, and this research evaluated the effects of various levels of ozone on the survival of these two pathogens. We designed a continuous type O3 treatment system that has four major components: (1) ozone generator using oxygen; (2) ozone concentration control by mixing with pure air; (3) continuous monitoring of ozone concentrations; and (4) ozone experiment chambers. Various levels of ozone (43.26, 87.40, and 132.46 mg·L−1) were produced in the ozone system, and subsequently, ozone was diffused through liquid manure. Liquid manure was exposed to ozone for multiple durations (30, 60, and 120 min). To determine the effectiveness of O3 in eliminating pathogens, time-series samples were collected and analyzed for determining the levels of S. typhimurium and E. coli O157:H7. Preliminary results showed that ozone concentrations of 132.46 mg/L, and exposure time of 120 min resulted in the reduced levels of E. coli and Salmonella. Low levels of ozone and limited exposure time were found to be less effective in pathogen removal potentially due to high solid contents. Additional studies carrying out experiments to evaluate the impacts of solids in combination with ozone concentrations will provide further insights into developing full-scale ozone-based treatment systems.