Environmental Engineering Reference
In-Depth Information
where
ΔC
Mineral
= Annual change in carbon stocks in mineral soils.
SOC
O
= Soil organic carbon stock in last year of inventory time period (i.e.,
40.83 mt C per hectare).
SOC
(
O-T
)
= Solid organic carbon stock at beginning of inventory time period
(i.e., 62 mt C per hectare).
D
= Time dependence of stock change factors which is the default time period
for transition between equilibrium SOC values (i.e., 20 years for cropland
systems).
Therefore, ΔC
Mineral
(SPC
O
- SOC
(
O-T
)
) ÷
D
= (40.83 - 62) ÷ 20 = -1.06 metric tons
C per hectare per year of soil organic C are lost. Consequently, the change in carbon
density from converting forestland to cropland would be -86.22 metric tons of C
per hectare per year of biomass plus -1.06 metric tons C per hectare per year of soil
organic C, equaling a total loss of 87.28 metric tons C per hectare per year (or -35.32
metric tons C per acre per year). To convert to carbon dioxide, multiply by the ratio
of the molecular weight of carbon dioxide to that of carbon (44/12), to yield a value
of -320.01 metric tons CO
2
per hectare per year (or -129.51 metric tons CO
2
per acre
per year).
Conversion Factor for Carbon Sequestered Annually by
One Acre of Forest Preserved from Conversion to Cropland
Due to rounding, performing the calculations given in the equations below may not
return the exact results shown. Negative values indicate CO
2
that is
not
emitted.
(-35.32 metric tons C per acre per year) × (44 units CO
2
÷ 12 units C) = -129.51
metric tons CO
2
per acre per year.
To estimate CO
2
not emitted when an acre of forest is preserved form conversion
to cropland, simply multiply the number of acres of forest not converted by -129.51
metric tons CO
2
per acre per year. Note that this calculation method assumes that
all of the forest biomass is oxidized during clearing (i.e., one of the burned biomass
remains as charcoal or ash). Also note that this estimate only includes mineral soil
carbon stocks, as most forests in the contiguous United States are growing on min-
eral soils. In the case of mineral soil forests, soil carbon stocks could be replenished
or even increased, depending on the starting stocks, how the agricultural lands are
managed, and the time frame over which lands are managed.
Propane Cylinders Used for Home Barbecues
Propane is 81.7% carbon. The fraction oxidized is 100% (IPCC, 2006; USEPA,
2012b). Carbon dioxide emissions per pound of propane were determined by multi-
plying the weight of propane in a cylinder times the carbon content percentage times
the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that
of carbon (44/12). Propane cylinders vary with respect to size; for the purpose of this
equivalency calculation, a typical cylinder for home use was assumed to contain 18
pounds of propane.
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