Design and Construction of a Micro-scale Anaerobic Digester/Power Process

Presentation: PowerPoint 

Author(s): Steve Cox Department of Civil & Environmental Engineering Virginia Tech

Abstract: Biogas is produced by microorganisms during anaerobic digestion of organic substrates. Biogas consists primarily of methane and carbon dioxide and has been used as an inexpensive and valuable renewable fuel for more than 100 years. Using anaerobic digestion to stabilize organic waste, produce biogas, and generate power is a well-studied process and quite common at large organic waste management sites such as wastewater treatment plants and landfills. The benefits of anaerobic digestion include the production of electricity, reduction of organic waste disposal costs, and nutrient recovery. However, the application of this technology at smaller sites is relatively rare although often financially and technologically feasible. The objective of this work is to demonstrate and promote anaerobic digestion/power generation systems for application at smaller organic waste management sites. During the course of a nine-month period, a team of senior-level engineering students working with academic and industry advisors designed and constructed the mobile anaerobic digestion/power generation process, demonstrating that this technology can be simple, reliable, and cost-effective on a small scale. The process consists of six primary components: A 22-ft trailer, digester feeding system, 1000-gallon digestion vessel, biogas collection and storage system, 7-kW power generation system, and the electrical energy distribution system. The process was fed waste food from a university dining hall at a rate of 15 lb. per day. Gas production was 58 ft3 biogas per day at 57% methane. The process has operated reliably since start-up.