Land Use, Land-Use Change and Forestry

Other reports in this collection Alternative approaches

Alternative approaches have been proposed to better address the temporal dimension of carbon storage. Most of these approaches are based on adopting a two-dimensional measurement unit that reflects storage and time-namely, the ton-year. Many authors have proposed the concept of a ton-year unit (Moura-Costa, 1996a,b; Fearnside, 1997; Greenhouse Challenge Office, 1997; Chomitz, 1998; Dobes et al., 1998; Tipper and de Jong, 1998; Fearnside et al., 2000; Moura-Costa and Wilson, 2000). The general concept of the ton-year approach is in the application of a factor to convert the climatic effect of temporal carbon storage to an equivalent amount of avoided emissions (the remainder of this section refers to this factor as the equivalence factor, or Ef ); this factor varies from 0.007 to 0.02 (Dobes et al., 1998; Tipper and de Jong, 1998; Moura-Costa and Wilson, 2000). This factor is derived from the "equivalence time" concept (referred to as Te in the remainder of this section): the length of time that CO2 must be stored as carbon in biomass or soil to prevent the cumulative radiative forcing effect exerted by a similar amount of CO2 during its residence in the atmosphere (Moura-Costa and Wilson, 2000). Chapter 2 describes the theory and methods used for determining Ef.

Figure 5-4: Projection of carbon stored in an afforestation project (with baseline assumed to be zero), illustrating the concept of equivalence-factor yearly crediting (ton-years). The project receives yearly credits calculated as the total amount of carbon stored in any given year, multiplied by an equivalence factor, Ef. Alternatively (in the case of stock change crediting with ton-year liability adjustment), credits could be given as carbon is stored (solid line); in case of any event leading to the release of carbon stored, the amount of credits to be returned would be calculated as the difference between the solid line and the dotted line at that point in time.

Irrespective of the method used to calculate the equivalence factors, they could be useful for the accounting of GHG benefits of LULUCF projects. Different applications have been proposed (Moura-Costa and Wilson, 2000); in practice, a combination of approaches can be used, as follows:

Figure 5-5: Projection of carbon stored in an afforestation project (with baseline assumed to be zero), illustrating the concept of equivalence-delayed full crediting. In this example, the project receives credits only after planted trees have grown and been kept for a period of time, Te.

(continues on next page)

Other reports in this collection