ENERGY RETURNED ON INVESTMENT (EROI) AND ENERGY PAYBACK TIME (EPT) EVALUATION ON ANAEROBIC TECHNOLOGY PRODUCING BIO-H2 AND BIO-CH4

摘要

Abstract The aim of this paper is to investigate energy sustainability of an Anaerobic Digestion technology using a Life Cycle Approach Thinking. We considered a stirred batch anaerobic reactor, working at different temperatures. The intensive parameters were experimentally tested at laboratory scale from 16℃ to 50℃, a scale-up procedure of the bench bioreactor was set up using a geometrical similarity. The production of bioH2+bioCH4 in the so called two-step process gives a positive net energy both in winter and in summer time, on the contrary on the only H2 production. The sustainability of the two-step technology is analyzed at 16℃ through two parameters: Energy Return On Investment (EROI) and Energy Payback Time (EPT). Results demonstrate the sustainability of the technology. An analogical model is elaborated in order to represent the energy flow of the whole process: it considers electricity, thermal energy and the energy amortization for materials used either for the construction of the reactor or for the chemicals. Working with EPT equal 1 at 35℃, the 31.15% of useful energy is accomplished.