Biogas production as a promoter of rural development

Abstract

Like many other small rural communities, Los Pinos (Buenos Aires province, Argentina) is surrounded by agricultural and livestock premises that generate large amounts of waste, which are normally disposed with little to no treatment. The resulting air, water, and soil pollution has created social conflicts throughout the years. Simultaneously, electric supply is unreliable and expensive, and there is no gas supply network; hence, cooking and heating systems are mainly based on firewood. Anaerobic digestion (AD) of livestock and agricultural wastes emerges as an appropriate technology to simultaneously solve the problems of environmental pollution and access to energy in rural areas, contributing to closing the water-nutrient-energy cycle [1]. The objective of this work is to provide an integral solution to the social and environmental problems by adding value to waste and promoting the diversification of the rural energy supply. To this aim, a transdisciplinary team was assembled to work with residents and local authorities to find the most technically and socially appropriate strategy. As a result, a Biogas Production Demonstration Unit (UDB) was designed and built. The UDB is comprised of i) a continuously stirred tank reactor (CSTR) operating under mesophilic regime, ii) a half-buried plug flow reactor (PFR) operating under seasonal soil temperature (10°-20° C), iii) a digestate drying area, iv) a biogas conditioning system, and v) an electric power generation unit. Both reactors are operated in series and were seeded with active sludge from a potato-industry biodigester operating under mesophilic regime. The PFR was acclimate to ambient temperature for over 6 months after seeding. The biogas conditioning system consists of a biofilter followed by an activated-carbon filter. The biofilter periodically sprinkles liquid fraction of the digestate over wood chips to immobilize sulfur-oxidizing bacteria [2]. After conditioning, the biogas is transformed into electricity and will power the town?s water pump. Additionally, the solid fraction of the digestate is dried and will be composted to obtain an agricultural-grade soil amendment while the remaining liquid fraction is recirculated. The technology used in the UDB is applicable to other small rural communities since all the modules have been designed to be easily replicated at a relatively low cost with little technification. Furthermore, the operation and management of the UDB will be overseen by a cooperative purposely created by the town?s residents, generating new jobs, and diversifying the rural economy