GREENHOUSE GAS EMISSION BASELINES ■ 37tribute 20 to 25 percent of global and national GHG inventories yet are usually
negligible in city-scale Scope 1–2 GHG accounting because much of the food
production occurs outside the geographic boundaries of cities; at the same
time, life in cities would not be possible without food consumption.
Which Scope 3 Items to Include?
Th is discussion suggests two criteria for inclusion of cross-boundary GHG
emission motivated by activities occurring within urban areas. First, these activ-
ities should be critical for the functionality of cities, and, second, the resulting
GHG emission should be signifi cant contributors at larger spatial scales, such
that their exclusion at the city scale creates a discontinuity in GHG accounting
across spatial scales. We suggest that Scope 1–2–3 emissions accounting not
be used in place of Scope 1–2 accounting, which may be preferable for carbon
trading schemes but be used to augment Scope 1–2 reporting.
Several urban areas have included various cross-boundary emissions on an
ad hoc basis; for example, GHG emissions associated with food consumption
in cities have been included for Paris (Mairie de Paris 2009), Delhi, and Kol-
kata (Sharma, Dasgupta, and Mitra 2002), with Delhi and Kolkata focusing
on nonenergy emission from rice and milk production only. Embodied emis-
sions from producing various construction materials such as cement, steel, and
asphalt have been included in inventories for Kolkata, Delhi, Denver, Paris, and
Seattle. In pioneering a holistic emissions inventory for Denver, Ramaswami
and others (2008) articulated a small set of Scope 3 inclusions critical for func-
tionality of cities; these included the following:
- Energy associated with transport of good and people outside city bound-
aries, essential for trade and commuter travel to and from cities, allocated
equally to origin-destination locations. - Embodied energy and associated GHG emissions associated with produc-
tion of key urban materials critical for life in cities, such as the following:- Food
- Transport fuels (other fuels already being accounted for)
- Water and waste water (if such production occurs outside city boundaries)
- Materials for shelter—chiefl y cement because it is the single second-
largest CO 2 emitter following fossil fuel combustion.
Th e de minimus rule (CCAR 2007) can be applied, yielding a stopping rule: that
is, no further Scope 3 activities need be included unless they show more than
a 1 percent increase in the GHG accounting of a city. (Note that cities may also
export CO 2 embodied in goods and services that needs to be accounted too;
the “net” is of interest.) Th us, applying a full Scope 1–2–3 accounting can be