124
Stocks and fl ows are certainly interrelated. Flows are the ‘material income’ to a
system, and any net addition to stocks (NAS) is limited through the conservation of
mass by direct material input (DMI) minus domestic processed outputs (DPO)
minus exports. Yet, the use of stocks by society determines the resource fl ows
needed to operate, maintain or expand the physical stock. The services from stocks
of infrastructure, machines and durable goods are closest to the interests of society;
the socio-economic metabolic framework is driven fi rst by stocks. Flows of resource
inputs and waste outputs are driven by the need for services provided by stocks
rather than the demand for the fl ows themselves (Müller et al. 2004 ; Pauliuk and
Müller 2014 ). For example, travel by automobile requires a fl ow of energy, but it is
the stock (the automobile) that enables the conversion of energy into the service of
mobility determines the amount and type of fuel used and resulting emissions.
Stocks in-use record the cumulative resource fl ows – materials and energy –
embedded in the infrastructure and artefacts of the socio-economic system. Through
their role in production, the age and effi ciency of stocks are key factors in the operational consumption of resource fl ows in the economy and related GHG emissions.
At the same time, the services from stocks are key for social and material
development.
3 Problem Shifting
An important issue in responding to global challenges is the danger of ‘problem
shifting’: the potential for an intervention that alleviates one challenge to exacerbate
the response to another. Without an integrated approach that encompasses stocks
and fl ows of materials and energy, such a trade-off is underestimated or even invisible. What follows is an example from Müller et al. ( 2013 ) using an indicator for the
carbon footprint of infrastructure stocks, the ‘carbon replacement value’ (CRV) of
the stocks, which is defi ned as the carbon emissions required to replace an existing
infrastructure stock or to build a new infrastructure stock using currently available
technologies. Müller et al. ( 2013 ) based their CRV on upstream carbon emissions
starting with primary production, CRV P . This indicator is used to estimate the carbon emissions caused by developing nations if they were to converge on the level of
service provided in industrialised nations. The CRV P for scenarios of infrastructure
development was calculated using a metabolic approach that incorporates stock
dynamics.
3.1 Sustainable Development and the Carbon Budget
Emissions from the operation of infrastructure are generally considered to be the
main concern in the standard energy and emissions approach to GHG accounting:
the models used, such as Davis et al. ( 2010 ), represent infrastructure stocks as
T.M. Baynes and D.B. Müller
Stocks and fl ows are certainly interrelated. Flows are the ‘material income’ to a
system, and any net addition to stocks (NAS) is limited through the conservation of
mass by direct material input (DMI) minus domestic processed outputs (DPO)
minus exports. Yet, the use of stocks by society determines the resource fl ows
needed to operate, maintain or expand the physical stock. The services from stocks
of infrastructure, machines and durable goods are closest to the interests of society;
the socio-economic metabolic framework is driven fi rst by stocks. Flows of resource
inputs and waste outputs are driven by the need for services provided by stocks
rather than the demand for the fl ows themselves (Müller et al. 2004 ; Pauliuk and
Müller 2014 ). For example, travel by automobile requires a fl ow of energy, but it is
the stock (the automobile) that enables the conversion of energy into the service of
mobility determines the amount and type of fuel used and resulting emissions.
Stocks in-use record the cumulative resource fl ows – materials and energy –
embedded in the infrastructure and artefacts of the socio-economic system. Through
their role in production, the age and effi ciency of stocks are key factors in the operational consumption of resource fl ows in the economy and related GHG emissions.
At the same time, the services from stocks are key for social and material
development.
3 Problem Shifting
An important issue in responding to global challenges is the danger of ‘problem
shifting’: the potential for an intervention that alleviates one challenge to exacerbate
the response to another. Without an integrated approach that encompasses stocks
and fl ows of materials and energy, such a trade-off is underestimated or even invisible. What follows is an example from Müller et al. ( 2013 ) using an indicator for the
carbon footprint of infrastructure stocks, the ‘carbon replacement value’ (CRV) of
the stocks, which is defi ned as the carbon emissions required to replace an existing
infrastructure stock or to build a new infrastructure stock using currently available
technologies. Müller et al. ( 2013 ) based their CRV on upstream carbon emissions
starting with primary production, CRV P . This indicator is used to estimate the carbon emissions caused by developing nations if they were to converge on the level of
service provided in industrialised nations. The CRV P for scenarios of infrastructure
development was calculated using a metabolic approach that incorporates stock
dynamics.
3.1 Sustainable Development and the Carbon Budget
Emissions from the operation of infrastructure are generally considered to be the
main concern in the standard energy and emissions approach to GHG accounting:
the models used, such as Davis et al. ( 2010 ), represent infrastructure stocks as
T.M. Baynes and D.B. Müller