Page 186 - Materials Chemistry, Second Edition

174 B. Ruggeri et al.

Fig. 3 Energy terms involved in an energy technology

Unlike other researchers in which EROI was used to evaluate the net energy of
such energy sources (Cleveland and O’Connor 2011; Guilford et al. 2011; Brand
2009), we used EROI and EPT to evaluate the sustainability of H 2 ? CH 4 pro-
duced by AD technology. The approach is quite similar, but some differences exist
linked to the useful energy. Numerically speaking, only an EROI [ 1 indicates a
sustainable process. It is important to consider also the EPT parameter: if a
technology has an EPT = 7 years and its operation lifetime is around 20 years,
with a construction time of 2 years, the first energy unit able to support the energy
service of the society will be available after 9 years, even if the technology has an
EROI [ 1.

2.3 EROI and EPT Tools

EROI is the ratio between the total amount of net energy delivered to society by a
technology during its working lifetime and the amount of total indirectly energy in