Page 104 - vol5_n2

234 IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 2
Evaluation of partial clinker replacement by sugar cane bagasse ash: CO2 emission reductions
and potential for carbon credits
self-generation for clinker production, and is calculated in a similar
manner to the term le_grid_clnk. All terms used for the calculation of the
term 〖BE〗linker are divided by annual production of clinker so that
the unit of the terms is ton of CO2 per ton of clinker.
5.1.2. Leakage
The second step of the calculation of emissions is called Leak-
age, which corresponds to “fugitive” emissions that occur outside
of the process due to burning of fossil fuels for the transport of raw
materials, fuels and additives to the plant. However, the methodol-
ogy quantifies these emissions only for the transportation of the
additive used in the project, since these tend to decrease when it
is reduced the amounts of clinker in cement. This type of emissions
is calculated using the following equation:
(4)
y y Blend y Blend trans add y BC P A L L × - = ) ,
, _ (
being Ly the total leakage emissions relating to the transportation
of additives in kt of CO2; Ladd_trans the transport-related emissions
of additives in tons CO2 per ton of the additive; Ablend, y the fraction
of additives in the Baseline cement and Pblend, y the fraction of ad-
ditives for the Project cement, both in tons of additive per ton of
cement. The term 〖BC〗y represents the total production of cement
for each year of the project in kt.
The burning of fossil fuels needed to transport the additive used
from its origin site to the plant is the main source of emissions of
the new scenario. The average distance of transportation, the fuel
used and the efficiency of the transport system used also influence
this amount. The term Ladd_trans synthesizes these emissions and is
given by:
(5)
y grid ADD conveyor add source add cons trans add ADD EF ELE Q C TEF D TF L /) ( /) ( _ 4 _ _ × + × × × =
being 〖TF〗cons the consumption of the vehicle in kg of fuel per km;
Dadd_source the average distance of transportation in km; TEF the fuel
emission factor used in kg of CO2 per kg of fuel; C4 a constant con-
version factor equal to 0.001 ton per kg; Qadd quantity of additives
carried per vehicle in one trip in ton; 〖ELE〗conveyor_add the annual
energy consumption for conveyor system for additives in MWh;〖EF〗grid the grid emission factor in ton of CO2 per MWh and 〖ADD〗y the annual quantity of additive consumed in ton.
5.1.3. Project emissions
The third step is the calculation of emissions of the cement pro-
duced in the project or Project emissions. The equations for cal-
culating this step are the same as those used in the Baseline
emissions, changing only the nomenclature of BE to PE. It can
be concluded beforehand that the terms 〖BE〗clinker and 〖PE 〗clinker
are equal if the clinker used in the project is the same as the cur-
rently produced, existing only differences in the amounts of clinker
in cement. Additionally, the terms 〖BE〗ele_ADD_BC and 〖PE 〗ele_ADD_BC
are also equal if there are no emissions associated with the prepa-
ration of the new additive. This way, the values calculated in the
equation 3 may be used for the determination of the emissions of
the project, summarized by the following equation:
(6)
BC ADD ele y Blend clin y BC PE P PE PE _ _ ) ,
ker , ( + × =
The ACM 0005 methodology provides that the grid emission fac-
tors used in the calculations shall be determined in accordance
with another methodology called Tool to Calculate the Emission
Factor for an Electricity System, also authored by the UNFCCC.
However, when there are precise and reliable local data, the adop-
tion of these predetermined values is also possible.
5.1.4. Emissions reductions
The calculation of emission reductions is given by:
(7)
) 1( ] ) ,
, [( y y y y BC y BC y L BC PE BE ER a
- × + × - =
being 〖ER〗y the annual reduction of CO2 emissions in kt; 〖BE〗BC,y
and 〖PE〗BC,y the total emissions in ton of CO2 per ton of cement on
the Baseline and Project, respectively; 〖BC〗y the total production
of cement for each year of the project in kt; Ly the total leakage
emissions relating to the transportation of additives in kt of CO2 and
the term ay represents an extra emission arising from the diversion
of additives from existing uses. That is, if the quantity of additives
that are effectively surpluses after application in the existing usage
is not sufficient to feed the project, the emissions reductions must
be averaged by the ay factor given by the rate between the quantity
of additives not surplus and total quantity of the additives used in
the project.
For the case of the use of SCBA there is no current use for this
additive, since its use as fertilizer aims more to final disposition of
waste than the harnessing of poor fertilizer properties of the ash.
This way, if the quantity of ash generated is able to supply the
project, the term ay will be null.
6. Hypothetical scenarios of CDM
implementation
The possibilities of application of the SCBA as an additive in the
manufacture of cement are numerous for great part of the nation-
al territory, in view of the large number of states that gather both
sugar cane and cement production. However, the ash transport
distance from the sugar cane mills to the cement factories is a de-
cisive factor that can derail some alternatives. Too long distances
can decrease the emissions reduction and, in some cases, may
increase emissions from cement production due to burning of fos-
sil fuels by transport vehicles which, in Brazil, are predominantly of
road type. This way, the southeast region, and especially the state
of São Paulo, which concentrates on its territory more than 60%