80
as the cost of building a city with the pedestrian realm one storey up above a ground
fl oor dedicated to service vehicles and personal rapid transit pods. Nonetheless,
sustainable transformation of today’s existing and expanding cities is where the
challenge lies.
Although not complete, the study of cities in Industrial Ecology has come a long
way since Allenby’s ( 1999 ) observation that the science had yet to be done. Progress
has been made with a combination of broad holistic analyses of urban metabolism –
the scale upon which differences are measured – and more detailed studies of specifi c resource fl ows or infrastructure systems – which reveal the inner workings of
the city. As more cities, hopefully, move towards greater practical application of IE,
then attention to both scales will be important. There is a need for further study of
material fl ows in cities; few studies have quantifi ed material stocks and fl ows with
as much detail as those in Lisbon (Niza et al. 2009 ) or Paris (Barles 2009 ). More
refi ned understanding of material fl ows will be necessary to address questions in a
couple of related future directions discussed below: increased application of industrial symbiosis at the city scale and examination of the thermodynamics of urban
metabolism.
Just how much potential is there for industrial symbiosis to be conducted at the
city scale and how much of such sharing or recycling of residuals is already taking
place? Examples such as the case of Kawasaki, Japan, where 565,000 tonnes of
potential waste per year are diverted through seven key material exchanges hint at
signifi cant potential for industrial symbiosis in cities (Van Berkel et al. 2009a , b ).
Drawing upon four examples of urban regions where waste exchange is practiced,
and citing several nineteenth and early twentieth century authors, Desroches ( 2002 )
argues that urban industrial symbiosis used to be relatively common. “The fact that
cities or regional economies… have probably always exhibited localized interindustry recycling linkages seems highly plausible” (Desroches 2002 : 35). He suggests that industrial symbiosis is a form of agglomeration effect that occurs due to
the high volumes and close proximity of waste-producing activities in cities. As
well as further empirical studies, perhaps there is potential to develop theoretical
economic models that describe such agglomeration effects. Further research might
also seek to determine the limits to which industrial symbiosis or other notions of
the circular economy can practically be applied in cities. Some categories of materials cannot be recycled or require so much energy as to be undesirable (Ayres 1997 ;
Allenby 1999 ; Allwood 2014 ).
A fi nal challenging topic, which will also inform the questions on industrial symbiosis, is the development of improved theoretical understanding of the urban
metabolism using thermodynamics. This is important for addressing concerns over
possible limits to the notion of sustainable cities. If cities were to pursue high levels
of effi ciency, and greater closing of material loops through increased industrial
symbiosis, what would be the repercussions, feedbacks or rebound effects? For
example, if today’s cities were able to cut their consumption of fossil-fuel energy
use in half, might that just result in the saved fuels being used to build more cities?
Nonequilibrium thermodynamics, as used by Bristow and Kennedy ( 2015 ) to understand the growth of cities, might tentatively offer insights into such questions. A
C.A. Kennedy
as the cost of building a city with the pedestrian realm one storey up above a ground
fl oor dedicated to service vehicles and personal rapid transit pods. Nonetheless,
sustainable transformation of today’s existing and expanding cities is where the
challenge lies.
Although not complete, the study of cities in Industrial Ecology has come a long
way since Allenby’s ( 1999 ) observation that the science had yet to be done. Progress
has been made with a combination of broad holistic analyses of urban metabolism –
the scale upon which differences are measured – and more detailed studies of specifi c resource fl ows or infrastructure systems – which reveal the inner workings of
the city. As more cities, hopefully, move towards greater practical application of IE,
then attention to both scales will be important. There is a need for further study of
material fl ows in cities; few studies have quantifi ed material stocks and fl ows with
as much detail as those in Lisbon (Niza et al. 2009 ) or Paris (Barles 2009 ). More
refi ned understanding of material fl ows will be necessary to address questions in a
couple of related future directions discussed below: increased application of industrial symbiosis at the city scale and examination of the thermodynamics of urban
metabolism.
Just how much potential is there for industrial symbiosis to be conducted at the
city scale and how much of such sharing or recycling of residuals is already taking
place? Examples such as the case of Kawasaki, Japan, where 565,000 tonnes of
potential waste per year are diverted through seven key material exchanges hint at
signifi cant potential for industrial symbiosis in cities (Van Berkel et al. 2009a , b ).
Drawing upon four examples of urban regions where waste exchange is practiced,
and citing several nineteenth and early twentieth century authors, Desroches ( 2002 )
argues that urban industrial symbiosis used to be relatively common. “The fact that
cities or regional economies… have probably always exhibited localized interindustry recycling linkages seems highly plausible” (Desroches 2002 : 35). He suggests that industrial symbiosis is a form of agglomeration effect that occurs due to
the high volumes and close proximity of waste-producing activities in cities. As
well as further empirical studies, perhaps there is potential to develop theoretical
economic models that describe such agglomeration effects. Further research might
also seek to determine the limits to which industrial symbiosis or other notions of
the circular economy can practically be applied in cities. Some categories of materials cannot be recycled or require so much energy as to be undesirable (Ayres 1997 ;
Allenby 1999 ; Allwood 2014 ).
A fi nal challenging topic, which will also inform the questions on industrial symbiosis, is the development of improved theoretical understanding of the urban
metabolism using thermodynamics. This is important for addressing concerns over
possible limits to the notion of sustainable cities. If cities were to pursue high levels
of effi ciency, and greater closing of material loops through increased industrial
symbiosis, what would be the repercussions, feedbacks or rebound effects? For
example, if today’s cities were able to cut their consumption of fossil-fuel energy
use in half, might that just result in the saved fuels being used to build more cities?
Nonequilibrium thermodynamics, as used by Bristow and Kennedy ( 2015 ) to understand the growth of cities, might tentatively offer insights into such questions. A
C.A. Kennedy