ICBE> About Emissions Trading> Calculating GHG Emissions
Calculating Greenhouse Gases

The IPCC has identified 6 greenhouse gases

Symbol Name Common Sources
CO2 Carbon Dioxide Fossil fuel combustion, forest clearing, cement production, etc.
CH4 Methane Landfills, production and distribution of natural gas & petroleum, fermentation from the digestive system of livestock, rice cultivation, fossil fuel combustion, etc.
N2O Nitrous Oxide Fossil fuel combustion, fertilizers, nylon production, manure, etc.
HFC's Hydrofluorocarbons Refrigeration gases, aluminum smelting, semiconductor manufacturing, etc.
PFC's Perfluorocarbons Aluminum production, semiconductor industry, etc.
SF6 Sulfur Hexafluoride Electrical transmissions and distribution systems, circuit breakers, magnesium production, etc.

Most RE systems can be credited with reducing three greenhouse gases: CO2, CH4 and N2O. These are all waste products from fossil fuel combustion.

In addition, RE systems reduce criteria pollutants which affect climate indirectly, cause acid rain, and are related to respiratory problems in humans and other animals. We track and certify those reductions as well, because some have a market value (SO2 & NOX), and others could attain commercial value in the future, especially if they reduce potential outlays in the health industry.

ICBE assigned emission reduction values

Greenhouse gases produced per kWh vary wildly from utility to utility and country to country. For initial registrations, the ICBE uses an approximate average to estimate emissions reductions. Full registration includes reduction estimation based on location-specific emission production figures sourced from the EPA, IEA, or equivalent authority in the country of registration.

Below are the GHG emission values used to express reductions achieved by 1 kWh produced from solar thermal, solar electric, wind and hydro-electric systems at initial registration into the ICBE Renewable Energy Database™.

They come from 1996 US electric utility related emissions, rounded to a convenient number.

Greenhouse Gases
CO2 1 kg
CH4 0.00001 kg
N2O 0.00001 kg
SF6 0.00000055 kg
Criteria Pollutants
CO 0.00015 kg
NMVOC's 0.00002 kg
SO2 0.005 kg
NOx 0.0025 kg

Global Warming Potential, or GWP

Each greenhouse gas has active radiative, or heat-trapping properties. To compare greenhouse gases, they are indexed according to their Global Warming Potential. GWP is the ability of a GHG to trap heat in the atmosphere relative to an equal amount of carbon dioxide. Carbon dioxide assumes the value one (1). Carbon dioxide, though the most prevalent, is the least powerful GHG.

Greenhouse gases can now be expressed in carbon dioxide equivalents. A unit you'll see often is MMTCDE, or million metric tons of carbon dioxide equivalents.

How to calculate MMTCDE:

To calculate emission reductions achieved by renewable energy systems, the assumption is that a utility would otherwise have provided the energy now produced by the RE system. Knowing how many grams of GHG's a utility produces to generate and deliver 1 kWh, combined with the usage characteristics and the performance of your system allows us to calculate GHG reductions. After certification, these reductions become eligible for trading.

To get a sense of scale, the table below shows 2000 US Electric Utility GHG Emissions expressed in million metric tons of carbon dioxide equivalents (MMTCDE).

CO2 CH4 N2O HFCs, PFCs, and SF6F6
5,840 7.5 14.9 14.4

These next graphs show greenhouse gases and their global warming potential, and GHG's from all sectors of the 1996 US economy, expressed in GWP.

CO2 1
CH4 21
N2O 310
HFC's 140 ~ 11,700
PFC's 6,500 ~ 9,200
SF6 23,900
GHG Pie Chart

The total US production of GHG's in 2000 was 7,000.1 MMTCDE, 14.2% above 1990 baseline levels.


Documentation of ERC's extended by the ICBE is in the public domain and available on this web site. RE systems are credited with Greenhouse Gas reductions (ERC's) as well as several other pollutants (where available) at the end of each calendar or production year. System owners can use their on-line account to update system info, and sell, retire, or re-invest their ERC's.

Please note that Renewable Energy (excluding biomass) is almost completely emissions free and eligible for a variety of emission reductions. Sequestration projects, however, where carbon is harvested from the atmosphere and stored in trees, only reduces carbon dioxide, not any other greenhouse gas.

The value of emission reductions is expected to rise as carbon taxes and other regulatory measures strengthen to meet the reduction targets negotiated under the Kyoto Protocol.