Carbon Footprint

Carbon Footprint

A carbon footprint is "the total set of greenhouse gases (GHG) emissions caused by an organization, event or product" ^[1]. For simplicity of reporting, it is often expressed in terms of the amount of carbon dioxide, or its equivalent of other GHGs, emitted.

The concept name of the carbon footprint originates from ecological footprint discussion.^[2] The carbon footprint is a subset of the ecological footprint and of the more comprehensive Life Cycle Assessment (LCA).

An individual, nation, or organization's carbon footprint can be measured by undertaking a GHG emissions assessment. Once the size of a carbon footprint is known, a strategy can be devised to reduce it, e.g. by technological developments, better process and product management, changed Green Public or Private Procurement (GPP), Carbon capture, consumption strategies, and others.

The mitigation of carbon footprints through the development of alternative projects, such as solar or wind energy or reforestation, represents one way of reducing a carbon footprint and is often known as Carbon offsetting.

By area:

 

Of products

Several organizations have calculated carbon footprints of products;^[3] The US Environmental Protection Agency has addressed paper, plastic (candy wrappers), glass, cans, computers, carpet and tires. Australia has addressed lumber and other building materials. Academics in Australia, Korea and the US have addressed paved roads. Companies, nonprofits and academics have addressed manufacture and operation of cars, buses, trains, airplanes, ships and pipelines. The US Postal Service has addressed mailing letters and packages. Carnegie Mellon University has estimated the CO₂ footprints of 46 large sectors of the economy in each of eight countries. Carnegie Mellon, Sweden and the Carbon Trust have addressed foods at home and in restaurants.
The Carbon Trust has worked with UK manufacturers on foods, shirts and detergents, introducing a CO₂ label in March 2007. The label is intended to comply with a new British public available specification (i.e. not a standard), PAS 2050,^[4] and is being actively piloted by The Carbon Trust and various industrial partners.^[5]

Of electricity

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The following table compares, from peer-reviewed studies of full life cycle emissions and from various other studies, the carbon footprint of various forms of energy generation: Nuclear, Hydro, Coal, Gas, Solar Cell, Peat and Wind generation technology.

The Vattenfall study found renewable and nuclear generation responsible for far less CO₂ than fossil fuel generation.

Emission factors of common fuels

Fuel/ Resource	Thermal g(CO2-eq)/MJth	Energy Intensity W·hth/W·he	Electric g(CO2-eq)/kW·he
Coal	&0000000000000092510000B:91.50–91.72 Br:94.33 88	&0000000000000002990000B:2.62–2.85[6] Br:3.46[6] 3.01	&0000000000000994000000B:863–941[6] Br:1,175[6] 955[7]
Oil	&000000000000007300000073[8]	&00000000000000033999993.40	&0000000000000893000000893[7]
Natural gas	&0000000000000068299999cc:68.20 oc:68.40 51[8]	&0000000000000002700000cc:2.35[6] oc:3.05[6]	&0000000000000664000000cc:577[6] oc:751[6] 599[7]
Geothermal Power	&00000000000000030000003~		&0000000000000040000000TL0–1[7] TH91–122[7]
Uranium Nuclear power		&0000000000000000190000WL0.18[6] WH0.20[6]	&0000000000000062500000WL60[6] WH65[6]
Hydroelectricity		&00000000000000000460000.046[6]	&000000000000001500000015[6]
Conc. Solar Pwr			&000000000000004000000040±15#
Photovoltaics		&00000000000000003300000.33[6]	&0000000000000106000000106[6]
Wind power		&00000000000000000660000.066[6]	&000000000000002100000021[6]

Note: 3.6 MJ = megajoule(s) == 1 kW·h = kilowatt-hour(s), thus 1 g/MJ = 3.6 g/kW·h.
Legend: B = Black coal (supercritical)–(new subcritical), Br = Brown coal (new subcritical), cc = combined cycle, oc = open cycle, T_L = low-temperature/closed-circuit (geothermal doublet), T_H = high-temperature/open-circuit, W_L = Light Water Reactors, W_H = Heavy Water Reactors, #Educated estimate.
These studies thus concluded that hydroelectric, wind, and nuclear power always produced the least CO₂ per kilowatt-hour of any other electricity sources. These figures do not allow for emissions due to accidents or terrorism.Lastly some relatively new green renewable electricity generation methods, wind power for example, emit no carbon during operation, but do leave a minor footprint during construction phase using the cradle-to-grave approach of the complete production life cycle.

Some content Courtesy of "wikipedia"