Page 182 - Materials Chemistry, Second Edition

170 B. Ruggeri et al.

Fig. 1 General layout of energy flow

power, solar energy, and organic refuse from the food chain could offer possible
solutions (Angenent et al. 2004).
However, we believe that it is also important to introduce the concept of energy
service, here intended as the amount of energy required by the end-user as useful
energy, i.e., the energy necessary to support human life, as outlined in Fig. 1.
Surplus energy flowing from each block in Fig. 1 depends from the technology
used, and it is of primary importance for society. Wealth, survival, art, army, and
even civilization itself is a product of surplus energy. The interplay of how much,
what kind (quality), and at what rate the energy is delivered determines the useful
energy. It gives the ability to the society to divert attention from life-sustaining
needs toward luxuries, such as art and scholarships including research and inno-
vation for the exploitation of different energy sources.
Among the primary energy sources, organic waste material (Evans 2001)is
approximately 60 % of daily refuse production. The technology pallet to use
organic waste ranges from biological processes (Pfeffer and Lieman 1976)to
thermal methods, such as gasification, pyrolysis, and incineration (Guéhenneux
et al. 2005) including the direct conversion of organic matter into electrical energy
through the use of Microbial Fuel Cell (Tommasi et al. 2012; Logan 2008;
Aelterman et al. 2006) as reported in Fig. 2.
Taking in mind Fig. 2, in order to select the most appropriate technology, it is
necessary to establish which criteria should be used to valorize the sources
(Sentimenti and Biorgi 2006). In this context, economic criteria on their own
appear to be inappropriate, because data can easily be manipulated according to
the working hypothesis and the conclusions might not be completely reliable
(Cleveland et al. 1984). Economists argue that the price of a technology or a fuel