Sources of Greenhouse Gas Emissions
Commercial and Residential Sector Emissions
Total U.S. Greenhouse Gas Emissions by Economic Sector in 2011
The residential and commercial sectors include all homes and commercial businesses (excluding agricultural and industrial activities). Greenhouse gas emissions from this sector come from fossil fuel combustion for heating and cooking needs, management of waste and wastewater, and leaks from refrigerants in homes and businesses. Indirect emissions, resulting from electricity consumed by homes and businesses, are discussed on the Electricity Sector page.
Residential and commercial activities contribute to emissions in a variety of ways:
- Combustion of natural gas and petroleum products for heating and cooking needs emits carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Emissions from natural gas consumption represent about 77% of the direct fossil fuel CO2 emissions from the residential and commercial sectors. Coal consumption is a minor component of energy use in both of these sectors.
- Organic waste sent to landfills emits CH4.
- Wastewater treatment plants emit CH4 and N2O.
- Fluorinated gases (mainly hydrofluorocarbons, or HFCs) used in air conditioning and refrigeration systems can be released during servicing or from leaking equipment.
More national-level information about emissions from the residential and commercial sectors can be found in the U.S. Inventory's Energy and Trends chapters.
Emissions and Trends
In 2011, direct GHG emissions from homes and businesses accounted for approximately 11% of total U.S. GHG emissions. Greenhouse gas emissions from homes and businesses have generally been increasing since 1990, but vary from year to year based on short-term fluctuations in energy consumption caused by weather conditions. Total residential and commercial GHG emissions have increased by less than 1% since 1990. Greenhouse gas emissions from on-site energy combustion in homes and businesses have only increased by about 1% since 1990 due to efficiency improvements in the residential and commercial sectors. However, indirect emissions from electricity use by homes and businesses have increased by 35% since 1990, due to increasing electricity consumption for lighting, heating, air conditioning, and appliances.
To learn about projected greenhouse gas emissions from the commercial and residential sectors to 2020, visit the U.S. Climate Action Report, 2010. (PDF) (193 pp, 3.1 MB)
Greenhouse Gas Emissions from Homes and Businesses
Reducing Emissions from Homes and Businesses
The table shown below provides some examples of opportunities to reduce emissions from homes and businesses. For a more comprehensive list of options and a detailed assessment of how each option affects different gases, see Chapter 8 of the Contribution of Working Group III to IPCC's Fourth Assessment Report.
|Type||How Emissions are Reduced||Examples|
|Homes and Commercial Buildings||Reducing energy use through energy efficiency.||Homes and commercial buildings use large amounts of energy for heating, cooling, lighting, and other functions. "Green building" techniques and retrofits can allow new and existing buildings to use less energy to accomplish the same functions, leading to fewer greenhouse gas emissions. Techniques to improve building energy efficiency include better insulation; more energy-efficient heating, cooling, ventilation, and refrigeration systems; efficient fluorescent lighting; passive heating and lighting to take advantage of sunlight; and the purchase of energy-efficient appliances and electronics. Learn more about ENERGY STAR.|
|Wastewater Treatment||Making water and wastewater systems more energy efficient.||Drinking water and wastewater systems account for approximately 3-4% of energy use in the United States. Studies estimate potential savings of 15-30% that are "readily achievable" in water and wastewater plants.  Learn more about Energy Efficiency for Water and Wastewater Utilities.|
|Waste Management||Reducing solid waste sent to landfills.
Capturing and using methane produced in current landfills.
|Landfill gas is the natural by-product of the decomposition of solid waste in landfills. It primarily consists of CO2 and CH4.
Well established, low-cost methods to reduce greenhouse gases from consumer waste exist, including recycling programs, waste reduction programs, and landfill methane capture programs.
|Refrigeration||Reducing leakage from refrigeration equipment.
Using refrigerants with lower GWPs.
|Commonly used refrigerants include ozone-depleting hydrochlorofluorocarbon (HCFC) refrigerants, often HCFC-22, and blends consisting entirely or primarily of hydrofluorocarbons (HFCs), both of which are potent greenhouse gases. In recent years there have been several advancements in refrigeration technology that can help food retailers reduce both refrigerant charges and refrigerant emissions.
Learn more about EPA's Greenchill Program to reduce greenhouse gas emissions from commercial refrigerators.
- EPA (2012). Energy Efficiency for Water and Wastewater Utilities. Accessed 03/13/2012
6,822 million metric tons of CO2 equivalent--what does that mean?
An Explanation of Units
A million metric tons is equal to about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons is roughly the same mass as 1 million small cars!
The U.S. Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is a little bit larger (about 10%) than a U.S. "short" ton.
GHG emissions are often measured in carbon dioxide (CO2) equivalent. To convert emissions of a gas into CO2 equivalent, its emissions are multiplied by the gas's Global Warming Potential (GWP). The GWP takes into account the fact that many gases are more effective at warming Earth than CO2, per unit mass.
The GWP values appearing in the Emissions webpages reflect the values used in the U.S. Inventory, which are drawn from the IPCC's Second Assessment Report (SAR). For further discussion of GWPs and an estimate of GHG emissions using updated GWPs, see Annex 6 of the U.S. Inventory and the IPCC's discussion on GWPs.