Environmental Engineering Reference
In-Depth Information
7.3.2 Resource efficiency implications of different cascade
configurations
Sirkin and Ten Houten (1994) proposed the concept of a 'cascade chain',
expanding the definition of resource cascading into an operational frame-
work for determining the efficiency and appropriateness of a given resource
exploitation within a given context. Their model uses four dimensions for
defining or describing a cascade:
resource quality, utilization time,
consumption rate and salvageability.
Resource quality refers to the extent to which a given resource is fitted to
the task being performed. Utilization time refers to the time span over which
the resource is used in the cascade. Consumption rate refers to the rate of
resource flow and is a fundamental dimension in relation to sustainability as
it relates to resource availability for coming generations. Finally, salvage-
ability refers to the degree to which the resource quality of a material can be
recirculated to the same chain or alternative cascade chains. The four
dimensions defined in the cascade chain model are used to describe the
differences in the role of AD from the three defined perspectives in Table 7.1.
Table 7.1
Description of AD cascades based on the four-dimensions proposed
by cascade chain theory
Perspective
Dimension
Multifunctional
Protagonist
Contribution
Resource
quality
Best fitted following
maximization of
environmental
sustainability criteria
Best fitted for AD
following
maximization of the
energy output
Available from the
agricultural and
industrial processes
already in place
Utilization
time
Maximized by
appropriate use of
different fractions of
biomass
Defined by the AD
process
Prolonged by the
introduction of AD
for the treatment of
by-products
Consumption
rate
Adjusted to fit
renewability of the
resources employed
Adjusted to fit the
energy demand
Fixed according to
the main use of the
biomass
Salvageability Optimal, as AD
potential for closing
cycles is fully
exploited
Allowed by the
incorporation of
digestate in the field
Defined by the other
industrial processes
involved
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