Understanding Consumption-Based Emissions

Recent work tracing carbon through our economic system has produced a clearer picture of how consumption activities act as an important driver of climate change. Analysis of consumption-based emissions sheds light on keys aspects of this relationship.

Consumption-based emissions inventories (CBEI) employ a comprehensive approach to estimating municipal consumption-based emissions by accounting for emissions associated with local consumption of goods and services, regardless of where they were produced. Emissions tied to goods produced locally for export are typically excluded.

This approach encompasses the full lifecycle emissions of goods and services, including those from production, pre-purchase transportation, wholesale and retail, use, and post-consumer disposal. The methodology is based on spending by households and government entities, and in certain inventory approaches, certain types of purchases made by businesses (e.g., capital and inventory formation).

Unsurprisingly, this type of emissions accounting typically results in a much higher total carbon footprint as it counts global, not just local, emissions related to a community’s economic activity. With the City of Portland, for example, the total emissions from the consumption-based approach were over twice the total emissions from the more traditional inventory method. For communities that don’t produce much of their own consumer goods and food, and consequently rely on imports from areas outside their boundaries, this affect may be amplified.

Community Total emissions from CBEI (MTCO2e) Total emissions from traditional inventory* (MTCOT2e)
*Methodologies and emissions counted may vary by community.
Portland, OR 15.8 million 7.9 million
San Francisco, CA 21.7 million 8.5 million
King County, WA 55 million 23.4 million

Other insights from CBEI results:

  • Over half of our carbon footprint comes from consumption of food, goods and services. The remainder comes from home energy use and transportation fuels - the traditional focus of many urban sustainability programs.

  • Household consumption contributes the majority of consumption-based emissions (e.g. in Oregon, over 75%) with government and businesses contributing the remainder.

  • The majority of consumption based emissions come from three categories: vehicles and parts, appliances (including heating/cooling) and food.

  • Taken as a whole, most emissions (at least 60%) are generated during the production (or pre-purchase) phase of consumption.

  • Emissions vary among the lifecycle stages. For most consumption categories, emissions are highest in the production phase. Others, such as vehicles, appliances and lighting, emissions are greatest during the use phase.

  • Products have greater carbon intensity, i.e. the amount of carbon associated with each dollar spent in that category, than services but within both, carbon intensity can vary greatly. For instance, certain materials (meat, for example) and services (airplane travel, garbage collection) have emissions intensities many times higher than the average.

Source: Portland CAP

Emissions intensity of consumption

Within a community’s consumption profile, consumption categories have varying carbon intensities. Analysis by the Oregon Department of Environmental Quality provides a detailed breakdown of emission intensities among consumption categories.

Oregon 2010 consumption-based emissions, pre-purchase emissions intensities
Pre-purchase life-cycle analysis (LCA) emissions (million MTCO2e) Final demand (in millions 2010$) Emissions intensities (kg CO2e/$)
Total 46.5 162,701 0.29
Appliances 0.3 445 0.63
Clothing 1.4 1,403 1.0
Construction 5.3 10,871 0.48
Electronics 1.5 4,459 0.34
Food and beverages 10.1 12,198 0.83
Furnishings and supplies 2.7 6,291 0.42
Healthcare 5 23,441 0.21
Lighting and fixtures 0 23 0.59
Other manufactured goods 4.5 8,841 0.51
Retailers 2.3 12,020 0.19
Services 6.9 37,513 0.18
Transportation services 3.7 2,344 1.56
Vehicles and parts 1.4 2,923 0.46
Water and wastewater 0.3 776 0.44
Wholesale 0.6 5,825 0.1
Other 0.6 33,328 0.02
Oregon 2010 consumption-based emissions, five-phase emissions intensities
Pre-purchase life-cycle analysis (LCA) emissions (million MTCO2e) Final demand (in millions 2010$) Emissions intensities (kg CO2e/$)
Total 747 168,198 0.44
Electricity 10.9 1,499 7.25
Fuels 16.3 4,339 3.76
Materials 25.8–35.8 49,818–68,217 0.52–0.52
Services 11.7–21.7 94,143–112,542 0.12–0.19

Some key findings from the DEQ analysis:

“With the exception of transportation, categories dominated by service expenses (such as healthcare, retailers, and services) tend to have lower emissions intensities than commodities that are primarily about materials, such as clothing, electronics, food/beverages, furnishings and supplies, and other manufactured goods.”

“It is important to note that emissions intensities can change simply as commodity prices change. For example, fuel prices in 2011 are higher than they were in 2005, and so the emissions intensity of fuels has fallen (emissions per dollar are lower now, simply because one dollar doesn’t purchase as much fuel as it did in 2005).”

Impact of consumption shifts

Understanding the relative carbon intensity of different forms of consumption can help inform a path toward more sustainable consumption. As pointed out in the King County, WA analysis:  

“Looking at emissions per dollar can help inform how to shift to lower-GHG consumption patterns. For example, study findings suggest that shifting spending from some GHG-intensive goods and services (such as clothing or electronics) to other categories (such as entertainment) could reduce GHGs.”

While shifting to lower emission intensive consumption generally helps to reduce the GHG impact, it’s important to look at the larger trends. As DEQ recently reported for 2014:

“Real emissions intensities (the emissions associated with producing one dollar of economic output) have fallen in all of the regions included in Oregon’s model (Oregon, US, and foreign) due to a variety of factors, including cleaner production and fuel shifting. At the same time, Oregon's overall consumption of goods and services has risen. Efficiency and other gains on the production side of the equation are offsetting increases in overall consumption (or vice versa) and Oregon’s consumption-based emissions are essentially 'treading water'.”