36
4.2.1 Integrated Assessment Models from an Industrial Ecology
Perspective
In general, one can say that industrial ecologists have a more refi ned notion of
industry as a complex system than what is currently characterized in most integrated
assessment models. IAMs trace the extraction, refi nement, and conversion of energy
carriers but lack a description of the life cycle of the conversion technologies. IAMs
model energy demand and energy effi ciency opportunities in industry, buildings,
and transport but lack a description of value chains and hence the interaction of different sectors. IAMs contain a description of material production as the most important industrial energy consumer but lack detail regarding the modeling of waste
generation and recycling, co-production, material demand, and associated environmental impacts.
In IAMs, the level of material recycling – if recycling is considered at all – is in
general not determined from the turnover of the industrial assets and products in the
use phase. Either the material stocks (mostly steel and aluminum) are modeled separately from capital and product stocks and an average lifetime is used, or there is
no connection at all between the extent of recycling and historic levels of material
consumption. Co-production, substitution of by-products, and industrial symbiosis
are only rudimentarily considered, if at all. Due to the focus on climate change,
other environmental impact categories, like toxicity or acidifi cation, are generally
not taken into account in energy systems models nor are mineral resource depletion
and the relation between ore grade and energy demand for extraction commonly
considered.
In a nutshell, we assert that integrated assessment models lack several features
that are central achievements of industrial ecology research. From the perspective of
our fi eld, the scenarios of society’s future metabolism constructed by IAMs lack
consistency and validity, which may compromise the credibility of the conclusions
drawn.
4.2.2 The Link Between the Prospective IE Models and IAMs
Integrating IE principles into IAMs will allow the latter to construct more consistent
and realistic scenarios of society’s future metabolism. Moreover, this integration
can increase the scope of IE research, and as a result, both research fi elds can move
forward. We present some ideas for how this integration could happen.
The general system structure of socioeconomic metabolism acknowledges three
types of processes: the industries, the markets, and the fi nal use phase (Pauliuk et al.
2015 ). There are canonical models for each process type. Industries are modeled by
production functions, markets by supply and demand curves, and the use phase by
dynamic stock models. We discuss each process type in turn.
(1) Industries : Both IAMs and IE models commonly use Leontief-type production
functions with fi xed technical coeffi cients and no substitution between inputs to
S. Pauliuk and E.G. Hertwich
4.2.1 Integrated Assessment Models from an Industrial Ecology
Perspective
In general, one can say that industrial ecologists have a more refi ned notion of
industry as a complex system than what is currently characterized in most integrated
assessment models. IAMs trace the extraction, refi nement, and conversion of energy
carriers but lack a description of the life cycle of the conversion technologies. IAMs
model energy demand and energy effi ciency opportunities in industry, buildings,
and transport but lack a description of value chains and hence the interaction of different sectors. IAMs contain a description of material production as the most important industrial energy consumer but lack detail regarding the modeling of waste
generation and recycling, co-production, material demand, and associated environmental impacts.
In IAMs, the level of material recycling – if recycling is considered at all – is in
general not determined from the turnover of the industrial assets and products in the
use phase. Either the material stocks (mostly steel and aluminum) are modeled separately from capital and product stocks and an average lifetime is used, or there is
no connection at all between the extent of recycling and historic levels of material
consumption. Co-production, substitution of by-products, and industrial symbiosis
are only rudimentarily considered, if at all. Due to the focus on climate change,
other environmental impact categories, like toxicity or acidifi cation, are generally
not taken into account in energy systems models nor are mineral resource depletion
and the relation between ore grade and energy demand for extraction commonly
considered.
In a nutshell, we assert that integrated assessment models lack several features
that are central achievements of industrial ecology research. From the perspective of
our fi eld, the scenarios of society’s future metabolism constructed by IAMs lack
consistency and validity, which may compromise the credibility of the conclusions
drawn.
4.2.2 The Link Between the Prospective IE Models and IAMs
Integrating IE principles into IAMs will allow the latter to construct more consistent
and realistic scenarios of society’s future metabolism. Moreover, this integration
can increase the scope of IE research, and as a result, both research fi elds can move
forward. We present some ideas for how this integration could happen.
The general system structure of socioeconomic metabolism acknowledges three
types of processes: the industries, the markets, and the fi nal use phase (Pauliuk et al.
2015 ). There are canonical models for each process type. Industries are modeled by
production functions, markets by supply and demand curves, and the use phase by
dynamic stock models. We discuss each process type in turn.
(1) Industries : Both IAMs and IE models commonly use Leontief-type production
functions with fi xed technical coeffi cients and no substitution between inputs to
S. Pauliuk and E.G. Hertwich