Concern over global warming and a rising sea level has prompted some companies to look into ways to offset their carbon emissions. The cost of sponsoring a renewable energy project is prohibitive for some companies (over $ 5 per ton of carbon emissions). Since the per-cap emissions of carbon in the USA total approximately 20 tons of carbon dioxide per year (based on an estimate of 6 billion tons and an estimated population of 300 million), it is untenable to expect the typical resident of the USA to sponsor his or her own carbon offset program if it costs as much as $ 100 per year.
Most companies that have examined the option of sponsoring tree plants as a way to reduce carbon footprint have encountered three questions:
(1) what kind of tree should be sponsored? And how much carbon can a typical tree absorb annually?
Much of that information was developed by the Organization of American States, on behalf of the electric power industry and other concerned groups back about 1980. It was further developed by the University of Oregon and Dr. Paiul Faeth of a consulting firm in Washington DC called Resources Management International (RMI) and was the basis for a carbon mitigation project in Guatemala funded largely by the US Government, on behalf of an electric power service organization, Applied Energy Services, located nearby Arlington, Virginia.
That project planted 54 million trees, mostly Leucaena leucocephala, which would be sufficient in annually removing more CO2 from the atmosphere than was emitted annually from the plant, which is located in Uncasville, Connecticut, USA. A second project on behalf of New England Electric Service (NEES) followed shortly thereafter.
The information came from studies of the annual growth of these species in conditions similar to those encountered in Guatemala and varous portions of these trees were annually weighed (trunk, branches, roots, leaflets, leaves). The finding was that such a tree already removed about 53 lbs. of Carbon Dioxide. The US Congress later simplified the calculation to 50 pounds, concluding that 40 such trees would annually remove and sequester a ton (2,000 lbs.) Of CO2.
Some agronomists believe that this figure might be conservative. Certain species of trees bring additional benefits to the soil that will result in more undergrowth. Also, the trees permanently shed leaves – these Leucaena Trees, for example, drop as much as 15 tons of leaves per hectare annually, That in itself represents about 20 lbs. of carbon per tree annually. Some of those leaves decay into soil and thus add to the forest mulch.
(2) How can we be sure the trees really are planed?
This issue was enough to kill most tree-planting efforts by green marketers in the late 1990s since there was not an easy way of verifying that the trees were really planted. As we will see later in this article, there are options that are now available, thanks to GPS.
(3) How can we be sure the trees will still be there ten years from now? Incentive programs can be put into place where the trees are monitored and if the local village can demonstrate that the trees planted had grown to maturity, then certain rewards can be delivered. For example, some tree planting organizations tie contracts of a new school to the successful protection of an area of newly planted trees.
Before closing this discussion, it may be of interest to discuss the "Forest Garden" approach, advocated by a tree planting organization in Silver Spring, Md. When the program combines trees with food crops and other plants, the total carbon sequestered per tree is higher. Since the forest garden itself is a "bankable" project (the local farmers derive more immediate income from the vegetables than from the trees), and the carbon sequestered also usually has a market value, it may be able to reducing atmospheric carbon with a profitable enterprise through this system.
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