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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 2
E. M. R. FAIRBAIRN
|
T. P. DE PAULA |
G. C. CORDEIRO
|
B. B. AMERICANO
|
R. D. TOLEDO FILHO
ing the burning of lime for the production of clinker and the burn-
ing of fossil fuels. The main additives commonly used are fly ash,
gypsum, blast furnace slag and limestone filler.
Like the cement industry, the sugar cane industry, currently under
a great expansion process, driven by growing demand for alterna-
tive fuels like ethanol, also figures as a strategic sector in the eco-
nomic and environmental global scenario, having been produced
about 730 million tons of sugar cane in the 2010 crop, respond-
ing the southeast for about 70% of the total [4]. The sugar cane
produced in Brazil serves as raw material for the production of
sugar and ethanol, generating about 190 million tons of bagasse.
Almost the entire bagasse generated on the sugar cane mills has
been burned for biomass energy harnessing through cogeneration
power plants, a process in which the final residue is the bagasse
residual ash. It is estimated that about 4.5 million tons of SCBA are
generated at each crop in Brazil [5].
Within this context, recent researches on the performance of ba-
gasse ash in concrete has been developed in the Laboratory of
Structures at COPPE/UFRJ, based on studies of the rheological,
thermal and mechanical properties and also associated with dura-
bility. The results obtained [5-9] show that there is great potential
for use of SCBA as pozzolan in cement production. Additionally,
because of the ash biomass origin, which burning does not contrib-
ute to the intensification of the greenhouse effect, the replacement
of clinker with ash allows the reduction of CO
2
emissions into the
atmosphere. One identifies, therefore, a promising scenario for the
deployment of CDM, especially in the southeast region of Brazil,
through the use of a sugar cane industry residue in the cement
industry, both heavily present in this region.
1.4 Objectives
This work aims to quantify the reduction of CO
2
emissions arising
from the partial replacement of Portland cement by SCBA and as-
sess the possibility of implementing a CDM.
1.5 Justification
In view of that the cement industry is responsible for approximately
5% [10] of global CO
2
emissions, the search for cleaner production
technologies capable of absorbing a residue which is largely gen-
erated in another industry and providing financial gains, reveals a
quite promising field of research and development. In this sense,
the Laboratory of Structures of COPPE/UFRJ has researched the
use of cementitious materials with new perspectives on dosage
and composition, where the use of SCBA with pozzolanic potential,
in the partial replacement of cement, has shown the best mechani-
cal performances and potential for CO
2
emission reductions in the
production of cement.
2. Feasibility of SCBA as an additive
in cement
The SCBA, for being rich in amorphous silicon dioxide, can be used
as pozzolan in cement manufacturing. Silica present in ash comes
mainly from the epidermis of plant cells, through the absorption
of monosilicic acid (H
4
SiO
4
) from the soil, and residual sand that
sometimes is not entirely removed on the sugar cane washing pro-
cess and is jointly burned with bagasse in steam boilers [6].
1.2 The Kyoto protocol and its mechanisms
On the basis of this evidence and within the framework of the UN-
FCCC, was drawn up in 1997 in the city of Kyoto in Japan, a Pro-
tocol whose main guideline would be the establishment of binding
targets of greenhouse gases emissions of developed countries,
so-called Annex I countries, in 5.2% compared to 1990 emissions,
for the period of 2008 to 2012.
The developing countries, or non-Annex I, within which Brazil is
classified, have not contributed with significant emissions due to
lower industrial activity and consumption over the last 150 years.
Therefore they would be exempt from emission reduction commit-
ment, but could contribute with the Protocol in other ways.
In order to create alternatives for emissions reductions to be more
flexible, the Protocol provides three mechanisms: Emissions Trad-
ing, where developed countries with unused emission quotas can
sell their quota for countries that have exceeded their targets for
the reduction; Joint Implementation, where countries with reduc-
tion targets can buy ERUs (Emission Reduction Units) of other
countries with targets that have implemented emission reduction
projects and want to sell these credits; and CDM (Clean Devel-
opment Mechanisms), where a country with targets can invest
in emission reduction projects in developing countries, acquiring
CER (Certified Emission Reductions), which unit equals 1 ton of
CO
2
. The investor country may redeem the credits in its emissions
in order to fulfill their goals, and the host country, beyond receiv-
ing technology, has the financial return generated from the sale of
CER. These three mechanisms compose the “carbon market” [1].
The Kyoto Protocol entered into force in 2002, after ratification of
Russia, and currently it has been ratified by a total of 184 coun-
tries, among which the United States, one of the countries which
have historically contributed with most of the world’s emissions,
are not included.
1.3 The Portland cement, the sugar cane bagasse
ash (SCBA) and the clean development
mechanism (CDM).
Several initiatives under the Kyoto Protocol and CDM occurred in
developing countries, especially Brazil, India and China. Many proj-
ects related to reducing emissions as the Nova Iguaçu landfill, state
of Rio de Janeiro, where there is conversion of methane from de-
composing garbage in CO
2
which greenhouse potential is 21 times
smaller; the use of biomass for energy generation; the utilization of
the waste incineration energy, as performed the
Usina Verde
, in the
UFRJ campus, also in Rio de Janeiro; the reforestation of degraded
areas; the use of alternative fuels; the reduction of the clinker ratio
in the cement production, where are emitted about 1 ton of CO
2
per
ton of cement [2], among numerous other ways of reducing emis-
sions, are receiving CER. All CDM projects, as exemplified above,
must meet, among other requirements, the requirement to use an
innovative technology, unknown by the market and the calculation of
emission reductions must follow a specific methodology, approved
and consolidated by the UNFCCC for that activity.
The method that involves the reduction of clinker in cement by in-
creasing the share of additives represents a promising alternative
for Brazil, which in 2010 had a production of 59.1 Mt of cement,
having the southeast of the country responsible for about 50% of
this amount [3]. Most emissions from cement production occur dur-