Page 183 - Materials Chemistry, Second Edition

Sustainability of (H 2 ? CH 4 ) by Anaerobic Digestion 171

Fig. 2 Technologies able to produce energy using Organic Wastes

automatically captures all the relevant features, but in a finite resource scenario,
this at least appears to be questionable. The life cycle assessment (LCA) (SETAC
1993), which takes into account all the aspects of such a technology (e.g., envi-
ronmental impact, safety, toxicity, energy use, and social issues together with
economics), is an alternative to a conventional economic analysis. One of the
difficulties of selecting a technology is the need to measure the sustainability level
of it.
To this aim, several approaches, ranging from a thermodynamic one (de Swan
et al. 2004) to a more industrial-oriented alternative (Apazagic and Perdam 2000;
De Simone and Popoff 1997), have been put forward in recent years to evaluate the
sustainability (Azapagic 1999; Laws et al. 1984). Hall et al. (2009) with reference
to energy sustainability, proposed that the most appropriate way to judge the
relative merits of different energy sources is to evaluate the ratio between
the amount of energy produced and the energy needed to produce it, known as the
energy return on investment (EROI). EROI, in its simplest form, measures the
output energy at the point of production or ‘‘mine mouth’’ (Murphy et al. 2011).