Consumption-based Greenhouse Gas Emissions Inventory for Oregon
Questions and Answers
- What’s a “GHG inventory”? How are inventories used?
A greenhouse gas (GHG) inventory is an accounting of gases
that contribute to climate change. These gases include
fossil-derived carbon dioxide, methane, nitrous oxide and others.
Greenhouse gas inventories can be conducted for organizations (such
as businesses) or for communities, such as at the scale of nations,
states or cities. Organizational and community inventories are not
the same. DEQ’s recently released consumption-based emissions
inventory is an inventory for a community (Oregon).
Inventories typically serve as the first step in planning for how a
community might reduce emissions. By understanding how a state or
city contributes to emissions, community members can better
understand opportunities to reduce them. Inventories also help
communities set and evaluate goals. For example, a community might
conduct an inventory in year X and then set a goal to reduce
emissions 10 percent below those emissions in 10 years. Finally,
inventories can help explain to policymakers, businesses and the
general public how their community contributes to emissions.
- Why did DEQ commission this consumption-based emissions
inventory after Oregon already completed a conventional GHG
In 2004, DEQ provided staff support to Governor
Kulongoski’s Advisory Group on Global Warming. One of DEQ’s support
roles was to staff a Technical Subcommittee on Materials and Wastes.
In the course of evaluating the GHG reduction potential of various
actions, it became clear that the state’s existing, conventional GHG
inventory excluded many of the emissions associated with materials,
simply because the emissions occur in other states, and the state’s
conventional inventory focuses on in-state emissions (with the
exception of emissions associated with electricity).
Over the next several years, other limitations of the conventional
inventory became apparent. Specifically, the conventional inventory
provides consumers and policymakers with an incomplete view of how
Oregon contributes to emissions, and by extension, opportunities to
One example of this is recycling. Collecting recyclables from homes,
as is required in many Oregon cities, requires fuel. Producing and
burning that fuel produces greenhouse gas emissions. Because the
combustion of fuel occurs in-state (and in-community) it is included
in conventional inventories at the state and city level. However,
when recyclables collected from households are used to produce new
products, the resulting reduction in greenhouse gas emissions can be
up to 40 times higher. Most of these emissions reductions occur in
other states, however, and thus are not reflected in the state’s
The conventional inventory also has the potential, by itself, of
providing misleading evaluation of change over time. For example,
in-state emissions might decrease even as consumption-based
In 2007, the Oregon Environmental Quality Commission encouraged DEQ
to develop a “fix” that would supplement the state’s conventional
inventory by providing an alternative view of how Oregonians
contribute to emissions – and by extension, opportunities to reduce
emissions. The commission also asked DEQ to try and get other
communities to adopt a similarly broad view. Once resources became
available, DEQ initiated the research required to develop this
supplemental, consumption-based emissions inventory.
- What’s included in this consumption-based emissions
inventory? What’s not included?
The inventory includes estimates of most emissions,
globally-distributed, associated with the life cycle of materials
and services, including electricity and fuels, consumed in Oregon.
These emissions are included regardless of whether they physically
originate in Oregon or elsewhere. Changes in atmospheric
concentration of greenhouse gases associated with land-use change
(for example, carbon storage by regional forests, or carbon releases
as tropical forests are replaced with plantations) are not included.
- So can DEQ tell me the emissions associated with
everything I buy (as a consumer) or make (as a producer)?
No. The model used to develop this inventory uses averages:
both for what Oregon consumers purchase and also emissions
associated with producing individual commodities. DEQ does not have
information on individual consumers, and the model does not provide
data about individual producers. DEQ understands that individual
consumers and producers may both vary widely from the average.
However, for the purpose of DEQ’s consumption-based inventory, which
is conducted at the scale of the entire state, use of averages is
- How does the consumption-based inventory compare with
Oregon’s conventional GHG inventory?
While the two inventories have some overlap, they’re
fundamentally different. The consumption-based inventory includes
estimates of most emissions, globally-distributed, associated with
the life cycle of materials and services, including electricity and
fuels, consumed in Oregon. The conventional inventory focuses on
in-state emissions but includes out-of-state emissions associated at
the point of electricity generation, for electricity used in Oregon.
Many in-state emissions included in the conventional inventory are
not included in the consumption-based inventory. In-state emissions
are only included in the consumption-based inventory if they are
somehow associated with in-state consumption. Emissions associated
with in-state producers making goods for export out-of-state are not
included in the consumption-based inventory, unless those exports
subsequently become part of supply chains that support in-state
While both inventories (conventional and consumption-based) count
some of the same emissions, the consumption-based approach
introduces a significantly new field of emissions that are not
included in the conventional inventory.
- So is the consumption-based inventory better than the
conventional inventory? More complete?
The two inventories are not more or less comprehensive than
each other. Rather, they each present an incomplete view of how the
state contributes to emissions. Viewing the two inventories together
offers a more comprehensive perspective; two different perspectives
are better than a single perspective.
- Can the results of the two inventories be reconciled?
The two inventories should not be simply added together, as
they share significant overlap, and it is challenging to identify
exactly where the overlap occurs, in part because the inventories
use fundamentally different approaches to estimate emissions. Of the
78 million metric tons of carbon dioxide equivalent in the 2005
consumption-based inventory, less than half (36 million metric tons)
originated in-state. Of the remaining 42 million metric tons, 24
originated elsewhere in the United States. Some but not most of
these other domestic emissions (24 million metric tons) are
associated with electricity consumption in Oregon, and are included
in both inventories. Other domestic but out-of-state
consumption-based emissions are not included in the conventional
inventory, nor are the 18 million metric tons in the
consumption-based inventory that occur in other nations.
- Why focus on consumption?
In economic terms, consumption is the root cause of all
economic activity. By extension, understanding the emissions
associated with Oregon’s consumption sheds more light on root
drivers of greenhouse gas emissions.
Second, a consumption-based approach is different enough from the
state’s conventional inventory so that it offers a significantly
different perspective. While both inventories count some of the same
emissions, both also uniquely count other emissions. Specifically,
the consumption-based inventory uniquely counts out-of-state
emissions associated with producing the products, services and fuels
consumed in Oregon. It also counts emissions associated with
producing fuels that are used to generate electricity consumed in
Emissions are also categorized and organized differently. Having two
perspectives of how Oregon contributes to emissions, as opposed to a
single perspective, broadens and deepens our collective perspective
- How might DEQ or others use the results of this
DEQ produced the inventory study to improve common
understanding about Oregonians’ impact on the environment. This is
akin to other information and research reports that DEQ periodically
prepares. DEQ does not have a specific policy or legislative agenda
that the inventory supports. Rather, DEQ believes that the
consumption-based inventory, when considered alongside the state’s
conventional GHG inventory, offers a more comprehensive
understanding of how the state contributes to climate change, and by
extension, opportunities to reduce that contribution to climate
Potential uses of the consumption-based inventory and supporting
research include the following:
- The state’s Global Warming Commission may use this inventory as
it identifies ways Oregon can reduce greenhouse gas emissions.
- If the state repeats a consumption-based inventory in future
years, it could use the inventory to help track Oregon’s progress at
reducing greenhouse gas emissions.
- The inventory identifies broad categories of consumption (such
as vehicles, appliances, food and manufactured products) that
contribute higher amounts of greenhouse gas emissions. These
categories would likely benefit from further study and/or action,
including voluntary action by producers and consumers.
- Similarly the study suggests that Oregon- and U.S.- made
products may, in some cases, result in lower GHG emissions than
products made in foreign countries. Further research is needed to
better understand this dynamic, and DEQ’s inventory could help to
justify and shape that additional research.
- The study may be useful as a screening tool to identify ways to
reduce GHG emissions associated with state and local government
- Businesses may find some of the underlying analysis useful for
evaluating greenhouse gas emissions associated with the products
they make or sell, and find ways to produce and deliver goods and
services in ways that reduce GHG emissions.
The inventory is not intended to replace any existing
inventories of greenhouse gas emissions. It does not list specific
recommendations on changing consumer/producer behavior and is not
intended as a “consumer guide” to reducing emissions. It does not
suggest changes to existing policies, and is not part of any effort
to impose a state “carbon tax” on products.
- Is DEQ telling Oregonians what to buy and what to eat?
No. While the inventory estimates emissions associated with
consumption, including consumption by households, and identifies
categories of emissions with higher emissions and emissions
intensities, DEQ is not telling Oregonians what to buy and eat. Some
members of the public may wish to use results of this study to help
inform day-to-day purchasing decisions. The analysis only considers
greenhouse gas impacts, and not the myriad other factors (financial,
environmental, social, health, etc.) that consumers also consider
when making purchasing decisions. The analysis also cannot help
consumers choose between competing brands of products. It can help
assess what categories of decisions matter most in terms of reducing
greenhouse gas emissions and addressing climate change – and so may
be useful as a tool for prioritizing efforts. Categories of
household consumption associated with the greatest greenhouse gas
emissions are personal vehicles, appliances, food and beverages, and
other manufactured products (clothing, medicines, consumer
electronics, furnishings, furniture, etc.). However, the report does
not make specific recommendations for purchasing or other behavior
- How does this project relate to the Oregon Global
Warming Commission’s “Roadmap to 2020”?
The Commission’s “Roadmap to 2020” lists actions that could
be taken to help the state meet its goal to reduce GHG emissions in
2020 to 10 percent below 1990 levels. These ideas are
recommendations to the Governor, Legislature, Oregon’s Congressional
delegation, local governments, businesses and Oregonians generally.
Completion of DEQ’s consumption-based emissions inventory, and
subsequent application of the results, is one of the recommendations
in the Roadmap. DEQ was one of many state agencies that provided
staff support to the commission as it drafted the Roadmap to 2020.
In conducting some of the technical analysis of options while the
Roadmap was developed, DEQ used a draft version of the
consumption-based inventory model.
- Does the consumption-based inventory include all
emissions associated with materials used in Oregon?
No. The consumption-based inventory only accounts of
life-cycle emissions of materials if they are consumed in Oregon (as
part of “final demand” by Oregon consumers), or otherwise are part
of the supply chain of consumption in Oregon. Materials that are
produced in Oregon and exported for ultimate use out-of-state are
- How does the consumption-based inventory treat
Waste recycling (and composting of some wastes) reduces
greenhouse gas emissions when viewed from a life-cycle perspective.
Since 2004, DEQ has estimated the life-cycle GHG reductions
associated with recycling and composting in Oregon. Of the estimated
GHG reductions of roughly 3.3 million metric tons of CO2e (carbon
dioxide equivalent) resulting from recycling and composting in 2005,
DEQ estimates that roughly one-third (or 1.1 million metric tons of
CO2e) are accounted for in the consumption-based inventory. For
details, including a fuller discussion of data sources and
methodology, please refer to this report:
- What do you mean by “final demand” and “consumers”?
“Final demand” is another term for “consumption.” It
includes only the goods and services purchased directly by “end
users” or “consumers.” “Consumers” include households and
governments. In certain instances, businesses are also counted as
“consumers.” The vast majority of purchases by businesses does not
contribute to final demand, but rather supports final demand as part
of supply chains. However, one small category of business purchases
is included in final demand: investment purchases, or the equipment
or inventory that businesses purchase but do not sell in a given
year. These definitions of “final demand” and “consumers” are
consistent with national economic accounting; the consumption-based
inventory relies on models derived from national economic accounts
to estimate emissions.
It should be noted that “consumption” is not the same as “use.” For
example, many businesses use electricity, but this use is not
counted as consumption, since consumption is limited to purchases by
households and governments as well as business investment purchases.
- What is a “carbon dioxide equivalent”?
Different greenhouse gases, such as carbon dioxide and
methane, have different impacts on climate. A “carbon dioxide
equivalent” is a means by which all greenhouse gases can be
expressed as a single number. For example, consistent with
international convention for greenhouse gas accounting at the
national scale, methane is treated as having a global warming
potential of 21 over a 100-year time period; compared to a global
warming potential for carbon dioxide of 1, this means that 1
kilogram of methane has an impact equivalent to 21 kilograms of
carbon dioxide. The emission of 1 kilogram of carbon dioxide and 1
kilogram of methane would be treated as 22 kilograms of carbon
dioxide equivalent (1 kilogram of carbon dioxide and 21 kilogram of
carbon dioxide equivalent from the 1 kilogram of methane).
- How are consumption-based emissions estimated?
Estimation begins with a widely used input-output model of Oregon’s
and the nation’s economy. This model estimates final demand by
Oregon consumers and relates it to all intermediate demand
(production) by producers required to satisfy the final demand. For
example, input-output models report how much sugar, flour,
chocolate, natural gas, electricity, cardboard, plastic, etc. are
required to produce a cookie. For each sector of the economy,
existing greenhouse gas inventories are used to estimate
industry-specific emissions intensities (emissions per dollar of
economic activity). For each of approximately 500 sectors of the
economy, these two factors (economic activity and emissions
intensities) are multiplied by each other to estimate domestic
emissions “upstream” of the consumer (economic production
necessarily to satisfy Oregon consumption is multiplied by emissions
per unit of production). These calculations are performed in
parallel for in-state and other domestic production required to
satisfy in-state consumption. Since an increasing faction of goods
and materials consumed in Oregon is produced internationally, a
separate, global input-output model is used to estimate
international emissions. These estimates are then added to estimates
of emissions associated with in-state consumption of energy
(electricity, fuels) and emissions associated with disposal of solid
waste generated in-state.
Please refer to the technical report for additional details.
- Where can I view the emissions intensity data?
Estimates of emissions intensities (emissions per dollar of
economic output) for different commodities are embedded in the
model, which is quite complex (six linked Excel workbooks, each with
6 to 12 worksheets). DEQ may make them available in a supplemental
report at a later date. If you are interested in viewing the
emissions intensities in the meantime, please contact
- What’s a “rebound effect”?
A rebound effect occurs when consumers engage in a
conservation activity that reduces emissions and saves them money,
then subsequently spend those savings in a way that increases
emissions. A classic example of this is when consumers retrofit
their furnace to a more energy-efficient model but then run it
longer, rationalizing that it doesn’t cost as much as it used to.
However, rebound effects can also cross between commodity groups.
For example, consumers might save fuel (and money) by driving less,
but then use the savings to purchase more goods. Underlying data in
the consumption-based inventory show that the (2005) emissions
intensity (emissions per dollar of economic output) of fuel is
approximately 5.8 kilograms of carbon dioxide equivalent per dollar,
while the emissions intensity of materials (all materials, averaged)
was approximately 0.5 kilograms of carbon dioxide per dollar. From
this, one can see that if a rebound effect as described above
exists, the net effect is still a reduction in greenhouse gas
emissions: for every dollar that consumers shift from fuels to
“average” materials, emissions fall by approximately 5.3 kilograms
of carbon dioxide equivalent (a 5.8 kg decrease offset by a small
0.5 kg rebound effect).
- Does the consumption-based emissions inventory only
address greenhouse gas emissions, or are other emissions (such as
toxics) also included?
The inventory only addresses greenhouse gas emissions.
- How accurate are the results?
It is impossible to say exactly. Because the
consumption-based inventory is largely derived from conventional
state and national inventories, it is likely no more accurate than
those inventories. Results are likely more accurate as the focus of
the inventory is broader, and are less accurate as the focus becomes
more refined. For example, estimates of emissions associated with
all in-state consumption are likely more accurate than estimates of
emissions associated with individual commodities (beer, shoes, pet
food, etc.). Estimates of emissions associated with broad categories
and subcategories of commodities are likely of intermediate
- What are the major limitations of the consumption-based
The inventory is derived from a model that depends on
estimates of consumer, government and business spending and trade
relationships based on national data scaled to Oregon. As a result,
the model may not reflect significant deviations in local behaviors
related to national averages.
Results also become less accurate as the level of analysis becomes
narrower. No analysis is possible below the level of individual
commodities (of which there are 509). The analysis is based on
commodity averages and does not distinguish between competing brands
within any given commodity group. Similarly, it does not distinguish
between different methods of production within any given commodity
(such as shade-grown vs. conventionally-grown coffee, or paper made
from recycled vs. virgin pulp feedstock) or between similar products
made of different materials (such as cotton vs. synthetic clothing).
- Who conducted the research?
The U.S. Center of the Stockholm Environment Institute
developed the consumption-based inventory, using staff based in
Washington and Massachusetts.
- Why didn’t DEQ hire an Oregon-based firm?
DEQ conducted a competitive recruitment. Stockholm
Environment Institute was selected as the applicant that scored the
highest, using the selection criteria outlined in the official
solicitation. Consistent with state law and procurement standards at
the time of the procurement, DEQ was unable to provide preference to
- How much did the study/inventory development cost?
DEQ spent $95,103 for the contract to develop the model,
technical report and summary report. The source of these funds was
the state’s tipping fee on solid waste disposal; no general fund
revenues were used. A significant portion of these costs were
up-front costs associated with developing the methodology, as this
type of project had not previously been performed at the level of a
state or locality in the United States. Subsequent analysis, if
conducted, should be less expensive.
- Why was the inventory only conducted for 2005?
It typically takes several years for emissions and economic
data needed to conduct an inventory to become available. For most of
the duration of the research effort, state (conventional) inventory
data was only available through calendar year 2005. Because the
consumption-based inventory relies on conventional inventory data
(to develop in-state emissions intensities), 2005 was the most
recent year for which a consumption-based inventory could be
produced. Shortly before the consumption-based inventory was
completed, the state of Oregon updated its conventional inventory
through 2008. Updated emissions estimates for 2005 were reflected in
the consumption-based inventory, but resource limitations prevented
DEQ from updating the consumption-based inventory to 2008.
- Does DEQ plan to update the inventory for future years?
DEQ has not committed to updating the consumption-based
inventory in future years. It expects to decide whether and how
frequently to update the inventory based in part on response to this
first (2005) inventory, and also after reviewing the costs to
maintain the inventory.
- Who else is doing this type of inventory?
Oregon was the first community in the United States to
commission this type of inventory. As of August 2011, the
consumption-based model developed by Stockholm Environment Institute
has also been applied to GHG inventories for King County
(Washington), the city and county of San Francisco, and the state of
- How does this compare with Metro’s GHG inventory?
The two inventories share a few things in common, but are
fundamentally different. Metro’s regional greenhouse gas inventory
is different from most other community GHG inventories in that it
includes an estimate of life cycle emissions of materials used in
the Portland metropolitan region. This has some overlap with DEQ’s
consumption-based inventory, but there are several important
differences. Metro’s inventory downscales (pro-rates) elements of
national inventory data to Metro conditions using population, while
DEQ’s consumption-based model is derived from economic modeling.
Metro’s inventory does not include foreign emissions, while DEQ’s
consumption-based emission does. And Metro’s view of materials is
based on materials produced in the U.S., while DEQ’s
consumption-based inventory is limited to materials consumed by
consumers (households, government and business capital).
- Are there additional resources available for state and
local governments interested in this type of inventory?
The West Coast Climate and Materials Management Forum has
produced an online toolkit that provides resources to help state and
local governments better incorporate materials management
considerations into their inventories and climate action plans.
While consumption-based inventories do not address all emissions
associated with materials used in a community, they do offer a
different way of understanding these emissions. The toolkit is
ICLEI – Local Governments for Sustainability USA is in the process
of producing a national protocol for community-scale greenhouse gas
inventories and reporting. Those protocols, once completed, may
offer some additional guidance.