Final Vermont Greenhouse Gas Inventory and Reference Case Projections, 1990-2030 Page: 2
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Final Vermont GHG Inventory and Reference Case Projection, 1990-2030
CCS, September 2007
Development of CO2e for BC+OMEmissions
We used similar methods to those applied previously in Connecticut for converting BC mass
emissions to CO2 equivalents.72 These methods are based on the modeling of Jacobson (2002)73
and his updates to this work (Jacobson, 2005a).74 Jacobson (2005a) estimated a range of 90:1 to
190:1 for the climate response effects of BC+OM emissions as compared to CO2 carbon
emissions (depending on either a 30-year or 95-year atmospheric lifetime for CO2). It is
important to note that the BC+OM emissions used by Jacobson were based on a 2:1 ratio of
OM:BC (his work in these papers focused on fossil fuel BC+OM; primarily diesel combustion,
which has an OM:BC ratio of 2:1 or less).
For Maine and Connecticut, ENE (2004) applied climate response factors from the earlier
Jacobson work (220 and 500) to the estimated BC mass to estimate the range of CO2e associated
with BC emissions. Note that the analysis in the northeast was limited to BC emissions from
onroad diesel exhaust. An important oversight from this work is that the climate response factors
developed by Jacobson (2002, 2005a) are on the basis of CO2 carbon (not CO2). Therefore, in
order to express the BC emissions as CO2e, the climate response factors should have been
adjusted upward by a factor of 3.67 to account for the molecular weight of CO2 to carbon
(44/12). In addition, Jacobson's modeling was based on total BC+OM, not just BC; hence, the
sum of these two species is needed for the transformation into CO2e.
For this inventory, we started with the 90 and 190 climate response factors adjusted to CO2e
factors of 330 and 697 to obtain a low and high estimate of CO2e for each sector. An example
calculation of the CO2e emissions for 10 tons of PM10 from onroad diesel exhaust follows:
BC mass = (10 tons PMo10) x (0.613 ton EC/ton PM1o) = 6.13 short tons BC
Low estimate CO2e = (6.13 tons BC) (330 tons CO2e/ton BC+OM) (3 tons BC+OM/ton BC) (0.907 metric
ton/ton) = 5,504 metric tons CO2e
High estimate CO2e = (6.13 tons BC) (697 tons CO2e/ton BC+OM) (3 tons BC+OM/ton BC) (0.907 metric
ton/ton) = 11,626 metric tons CO2e
NOTE: The factor 3 tons BC+OM/ton BC comes directly from the modeling assumptions used by
Jacobson (2002, 2005a; i.e., 2 tons of OM/ton of BC).
For source categories that had an OM:BC mass emission ratio >4.0, we zeroed out these
emission estimates from the CO2e estimates. The reason for this is that the net heating effects of
OM are not currently well understood (overall OM is thought to have a negative climate forcing
72 ENE, 2004. Memorandum: "Diesel Black Carbon Calculations - Reductions and Baseline" from Michael
Stoddard, Environment Northeast, prepared for the Connecticut Stakeholder Dialog, Transportation Work Group,
October 23, 2003.
73 Jacobson, 2002. Jacobson, M.Z., "Control of fossil-fuel particulate black carbon and organic matter, possibly the
most effective method of slowing global warming", Journal of Geophysical Physical Research, volume 107, No.
D19, 4410, 2002.
74 Jacobson, 2005a. Jacobson, M.Z., "Updates to 'Control of fossil-fuel particulate black carbon and organic matter,
possibly the most effective method of slowing global warming", Journal of Geophysical Research Atmospheres,
February 15, 2005.Vermont Department of I-2 Center for Climate Strategies
Environmental Conservation www.climatestrategies.us
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Center for Climate Strategies. Final Vermont Greenhouse Gas Inventory and Reference Case Projections, 1990-2030, text, October 2007; Washington, DC. (https://digital.library.unt.edu/ark:/67531/metadc226803/m1/90/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .