A few authors have stated that for a process to be energetically sustainable, it needs to produce
more usable energy than the one required for its operation. Furthermore, its potential environmental
impacts need to be evaluated to allow for a thorough picture of its sustainability. In this study, a Life
Cycle Assessment (LCA) was performed to investigate the potential environmental impacts and energy
balance of a pre-defined configuration. The studied system consisted of a bioH2 and biogas production
process from the organic fraction of municipal solid waste in a two-stage bioreactor, of 2.1 and 2.75
liters respectively. The analysis enabled a comparison of both stages' energy and environmental
performance, as well as the identification of the major energy consumption inputs of each stage. The
scenarios investigated for both processes were based on results from (i) a hydraulic retention time for
the dark fermentation process of 4 days and (ii) a hydraulic retention time of 5 days. The LCA was
carried out with the openLCA v. 1.8.0 program, with the functional unit of 1 kJ of produced gas, and
both CML 2 baseline 2000 and ReCiPe Midpoint (H) were applied as Life Cycle Impact Assessment
(LCIA) methods. The results indicated that the dark fermentation process of OFMSW for bioH2
production in the first stage had the best net energy balance of all the systems. In contrast, the
methanogenesis of volatile fatty acids (VFA) in the second stage for biogas production had the lowest
environmental impacts per kJ produced. The energy balance of the conventional anaerobic digestion of
the OFMSW was performed for comparison, with the conclusion that the proposed configuration
presented higher net energy production than the conventional anaerobic digestion process
