CanopyCo carbon offsetting and reforestation in Ecuador, South America.

Frequently Asked Questions

  What are greenhouse gases (GHG's)?  

There are six greenhouse gases covered by the international convention on climate change. They are quoted below along with their Global Warming Potential (GWP) and their atmospheric residence time:

Carbon dioxide (CO2); has a variable atmospheric lifetime, and cannot be specified precisely. Recent work indicates that recovery from a large input of atmospheric CO2 from burning fossil fuels will result in an effective lifetime of tens of thousands of years. Carbon dioxide is defined to have a GWP of 1 over all time periods. Main CO2 sources are the burning of fossil fuels and deforestation.

Methane (CH4) has an atmospheric lifetime of 12 3 years and a GWP of 62 over 20 years, 23 over 100 years and 7 over 500 years. The decrease in GWP associated with longer times is associated with the fact that the methane is degraded to water and CO2 by chemical reactions in the atmosphere. Methane emissions are from pipeline leakage, livestock and paddy rice farming, land use and wetland changes and landfill sites.

Nitrous oxide (N2O) has an atmospheric lifetime of 120 years and a GWP of 296 over 100 years. Agriculture, primarily the use of chemical fertilizers has lead to higher N2O concentrations.

Hydroflourocarbons eg HCFC-22 which has an atmospheric lifetime of 12.1 years and a GWP(100) of 1700. Used in refrigeration to replace CFC's after they were realised to be ozone depleting.

Perfluorocarbons (PFC's) eg Tetrafluoromethane which has an atmospheric lifetime of 50,000 years and a GWP(100) of 5700. These compounds are used in refrigeration units and fire extinguishers.

Sulphur hexafluoride (SF6) has an atmospheric lifetime of 3,200 years and a GWP(100) of 22000. This is the most potent of all greenhouse gases, but thankfully the least prominent; it is widely used in the electric industry.

In addition other compounds such as chloroflourocarbon (CFC's), used in refrigeration systems as well some fire suppression systems and manufacturing processes, are ozone depleting, creating further climatic changes. One of these, CFC-12, has an atmospheric lifetime of 100 years and a GWP(100) of 10600.


  Why is there such variability between different carbon offset organizations?  

If you compare different organizations websites there are variations of total CO2 emissions for the same flight route, and also the subsequent costs for off setting them. This is because carbon offsetting, although extremely beneficial, is still not an exact science and involves many variables, which can vary from source to source; from the information for carbon dioxide emissions, to the type of offset being offered.

For instance, in our carbon offsetting data, we have provided emissions figures both with and without consideration to Radiative Forcing (the total climate impact of a flight including an approximation of other (non CO2) pollutants emitted by planes). The radiative forcing index (RFI) is a factor of between 2 and 4; we are using the prudent average of 3 in our numbers, though the IPCC (International Panel on Climate Control) is still investigating this effect.

For calculating carbon dioxide emissions CanopyCo used the UK governments' DEFRA Passenger Transport Emission Factors report from June 2007.

For calculating carbon sequestration, data has been derived using various available sources, and tends to the conservative. We are in the process of studying the carbon sequestration properties of the native trees we are planting in their pertinent eco-systems, and until further data is collected we are using an average sequestration of 50 lbs carbon dioxide per tree per year.

  How do trees and forests help our atmosphere?  

Trees grow using a biological process called photosynthesis that converts water and atmospheric carbon dioxide into food compounds, namely glucose, and oxygen. Using these food compounds, the tree has the energy for growth, and it is this growth that sequesters carbon absorbed from the atmosphere as CO2. Roughly 50% by weight of a tree is carbon, and so forests can be considered as huge stores of carbon.

As carbon dioxide is the most abundant of the greenhouse gases, and also the primary anthropogenic gas emitted, the trees serve as an important sponge to remove carbon dioxide from the atmosphere.

How quickly trees absorb carbon dioxide depends on a few factors namely; tree specie, location in terms of altitude and ecosystem, age (younger, fast growing trees absorb more CO2 than mature trees) and also forest management. When trees eventually die and decay, the stored carbon is released back into the atmosphere as CO2, contributing to climate change.

When considering a forest system, after the trees mature and begin to die, new growth within the forest will compensate for the carbon dioxide released by decaying trees, so the system effectively becomes carbon neutral. But growing forests are referred to as carbon sinks as the carbon sequestered is greater than the carbon emitted.

When wood is harvested large quantities of carbon dioxide are released into the atmosphere (think of the waste created when extracting just a few planks) and so the preservation of forests is extremely important for the climate, as through their destruction, the huge volumes of carbon stored are released into the atmosphere.

  Some argue that planting trees is not the best way to offset emissions, is this true?  

There is a great deal of discussion concerning this point, however a two-fold problem exists; that of the current high levels of atmospheric CO2 and that of future emissions of CO2. Planting trees now will help the former, whilst conserving existing forests, changing our lifestyles and developing alternative energies will help with the latter. Tree planting is therefore one part of the complex global climate change solution.

  What is Radiative Forcing?  

Aircraft emissions in conjunction with other anthropogenic sources are expected to modify atmospheric composition (gases and aerosols), hence radiative forcing and climate.

Atmospheric changes from aircraft result in three types of processes: direct emission of radiatively active substances (e.g. CO2 or water vapour); emission of chemical species that produce or destroy radiatively active substances (e.g. NOx, which modifies ozone (O3) concentration); and emission of substances that trigger the generation of aerosol particles or lead to changes in natural clouds (e.g. contrails).

Radiative Forcing Index (RFI) is a measure of climate change from all green house gases and not just that of fossil carbon. The RFI expresses the warming effects of other GHG pollutants as a common unit, CO2e, or carbon dioxide equivalent.

This information was sourced through the following links where yet further details can be found;

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