23
4. Carbon emissions reduction levers
This chapter analyses strategies or levers for reducing
the CO
2
emissions footprint of cement production
and for supporting the
global cement industry in
achieving the roadmap vision pathway by:
z
Improving energy efficiency:
deploying
existing state-of-the-art technologies in new
cement plants and retrofitting existing facilities
to improve energy performance levels when
economically viable.
z
Switching to alternative fuels (fuels that
are less
carbon intensive than conventional
fuels):
promoting the use of biomass and waste
materials as fuels in cement kilns to offset the
consumption of carbon-intensive fossil fuels.
Wastes include biogenic and non-biogenic waste
sources, which would otherwise be sent to a
landfill site, burnt in
incinerators or improperly
destroyed.
z
Reducing the clinker to cement ratio:
increasing
the use of blended materials and the market
deployment of blended cements, to decrease the
amount of clinker required per tonne of cement
or per cubic metre of concrete produced.
z
Using emerging and innovative technologies
that:
z
contribute to the decarbonisation of electricity
generation by adopting EHR technologies to
generate electricity from recovered thermal
energy, which would otherwise be wasted,
and support the adoption of renewable-based
power
generation technologies, such as solar
thermal power.
z
integrate carbon capture into the cement
manufacturing process for long-lasting
storage or sequestration.
Alternative binding materials
offer potential
opportunities for process CO
2
emissions reductions
by using different mixes of raw materials or
alternatives
compared to PC, although their
commercial availability and applicability differ
widely. However, there is currently no independent,
publicly available and robust life-cycle assessment
for alternative binders or a comparative
quantification of production costs. This makes it
premature to include them in a techno-economic-
based evaluation of least-cost technology pathways
for cement production.
The CO
2
emissions reduction impact of these levers
is not always additive since they can individually
affect the potential for emissions reductions of other
options. For instance, the
use of alternative fuels
generally requires greater specific thermal energy
and electricity due to their higher moisture content
than fossil fuels, the operation of the kiln at greater
excess air levels compared to conventional fossil
fuels and the pre-treatment of alternative fuels.
The integration of carbon capture equipment typically
increases the specific energy intensity of cement
manufacture, as additional energy is needed to
operate the CO
2
separation and handling processes.
The global analytical results
discussed in this roadmap
result from the aggregation of analysing the net
impact of the cost-optimal combination of these
strategies within 39 specific regional contexts.
Improving energy efficiency
Energy efficiency improvements provide
0.26 GtCO
2
or 3% of the cumulative CO
2
emissions savings by 2050 globally in the 2DS
compared to the RTS. This is equivalent to 12%
of current direct CO
2
emissions of global cement
production.
Rotary dry-process kilns are currently the process
technology that is most widely deployed for cement
production. Dry kilns have lower energy intensities
than
wet-process kilns, as they operate with a lower
level of raw material moisture content, thereby
reducing the energy requirement for evaporation
of water. The global average thermal energy
intensity of clinker decreases by 10% from current
levels by 2050 through the use of energy efficiency
improvements and adoption of state-of-the-art
technology in replacement
and new capacity
additions, to support the direct carbon emissions
constraint in the 2DS.
Dry-process kilns with a precalciner, a multistage
cyclone preheater, and multichannel burners
17
are considered state-of-the-art technology for
clinker production. They lead to best available
energy performance levels of 3.0-3.4 GJ/t
clinker
18
based on empirical data and theoretical modelling
in the European context (ECRA and CSI, 2017).
17. Modern multichannel burners can operate with alternative fuels
by enabling optimal combustion conditions with varying fuel
mixes (ECRA and CSI, 2017).
18. Thermal energy intensity range based on a six-cyclone stage
preheater.
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