An Introduction to Anaerobic Digestion of Organic Wastes

The problem of waste disposal from a myriad of industries, is becoming increasingly acute, the world over. The burning of such wastes in open dumps or in poorly designed incinerators could be a major source of air pollution (Ndegwa and Thompson. Bioresour Technol 76:107–112, 2001). On the other hand, open dumps and poorly designed sanitary landfills can pollute surface and ground waters causing public health hazards. Meanwhile, the unavailability and rising cost of land near urban areas have made dumps and landfills increasingly expensive and impractical. The production of both livestock and grain on the other hand has increasingly relied on enormous chemical and energy inputs, leaving soils depleted of indigenous nutrients and organic matter, and resulting in wide-scale surface and groundwater contamination. As discussed earlier, recycling and utilization of organic wastes and by products through development of an economically viable, socially accepted and eco-friendly technologies are required. Over the years an array of innovative ideas for the utilization of these wastes have been put forward (Callaghan et al. Bioresour Technol 67:117–122, 1999) to increase productivity and to meet the heavy demand for food of the growing population (Jeyabal and Kuppuswamy. Eur J Agron 15:153–170, 2001). But these wastes could not be fully exploited without a viable technology for their economic recycling. It is well demonstrated that both fresh and composted amendments over these waste materials are potent to stimulate soil biological activities. Fresh wastes produces an initial burst of biochemical activity by the releasing easily degradable organic compounds whereas compost induces lower biochemical activities but more resistance to soils (Masciandaro et al. Soil Biol Biochem 32:1015–1024, 2000). Biological treatments plays a pivotal role in treating organic wastes these days. Among them, anaerobic digestion is frequently the most cost effective method because of the high energy recovery and its limited environmental impacts. Biogas production throughout Europe, could reach over 15 million m3/day of methane reported during 1998 (Tilche and Malaspina. Biogas production in Europe. Paper presented at the 10th European conference biomass for energy and industry, Wurzburg, 8–11 June, 1998). Presently, biogas production is considered to be an inevitable way of energy production.