CARBON CAPTURE
I CO2 – a catalyst for change
by David St Angelo, Joule,
USA
Cement production in 2014 is expected to surpass 4bnt in 2014, resulting
in carbon dioxide emissions by the cement sector of roughly the same level.
At the same time, the world is looking for increasing energy supplies and
therefore the conversion of CO2 emitted by cement plants into a usable
fuel is a compelling option.
R
ather than waste or store CO2
underground, the transformation
of such emissions into a readilyavailable and potentially low-cost carbon
feedstock offers an attractive opportunity.
However, the nature of the CO2 molecule
gives rise to specific issues in this conversion process. The molecule’s thermodynamic stability challenges its use as
a feedstock. If CO2 is to be used as a
feedstock, it will need to be reduced – a
process which is slow and requires energy.
Converting CO2 from cement plants to fuel: using an ubiquitous
waste product to meet one of the world’s key challenges
Catalyst for change
A catalyst could help in this transformation
process, but to date, few simple, low-cost
catalytic solutions have been identified.
However, this may be about to change. A
new type of catalyst and transformation
process capitalises on the availability of
CO2 from cement plants and other carbon
emitters.
The biocatalyst is engineered for direct
and continuous production of fuel as a
product of photosynthetic metabolism.
Unlike algae, which uses CO2 to produce a
lipid precursor for biofuel production, this
biocatalyst produces and secretes fungible
fuel molecules, including hydrocarbons
for diesel and jet fuel, without the need
for complex biomass growth, collection
and multistep downstream processing.
A catalyst could help in this
transformation process, but to
date, few simple, low-cost catalytic
solutions have been identified.
However, this may be about to
change. A new type of catalyst
and transformation process
capitalises on the availability of
CO2 from cement plants and other
carbon emitters.
The biocatalysts are self-replicating before
a ‘carbon switch’ diverts 95 per cent
of the carbon from cell growth to fuel
production.
The entire process – from photon
capture and CO2 mixing to product
generation and initial separation – takes
place in a SolarConverter® system.
This modular integrated bioreactor can
achieve replicable productivity whether
installed across 100 or 1000 acres, and
scales readily, dependent on insolation
INTERNATIONAL CEMENT REVIEW MAY 2014
and availability of non-arable land, nonpotable water and waste CO2. The wide
availability of these resources has enabled
the identification of thousands of potential
fuel production sites around the world.
For instance, using only 0.5 per cent of
global emissions, or eight per cent of
those attributed to the cement sector,
would be sufficient to sustain 1m acres of
production, resulting in up to 94.6bn litres
of ethanol or 56.8bn litres of diesel per
year.
CARBON CAPTURE
The SolarConverter system in action
at the demonstration plant in Hobbs,
New Mexico, USA
Working principle
A typical fuel production plant may
encompass 1000 acres and modular
SolarConverter production units. Each unit
contains engineered biocatalysts, nonpotable water and nutrients. Waste CO2 is
pumped in from an industrial emitter such
as a cement plant. The CO2 keeps the
biocatalysts in motion, maximising their
exposure to sunlight to drive photosynthesis. Charged by the sunlight, the catalysts
consume the carbon dioxide and continuously produce fuel, which is secreted into
the liquid medium. The medium circulates
through a separator that extracts the end
product, which is sent to a central plant for
final separation and storage.
This process takes place continuously for
several weeks before the module is flushed
and reinoculated on a phased basis.
A winning proposition
The exhaust stream of a cement works
offers an outstanding CO2 feedstock for
this transformation process. A plant flue
gas stream will contain 15-30 per cent
of CO2 by volume, or about 375-750x
atmospheric concentration. This higher
concentration translates into lower fuel
facility pumping costs as the volume of gas
that must be distributed around the unit is
lower. In addition, the high concentration
also enhances the gas phase mass transfer
of a reactor system. An exhaust stream
can be tapped at the point just after induction draught booster fans, located before
the emissions stack. This stream can be fed
into the fuel production process with minimal pretreatment, which consists primarily
of waste heat recovery, acid gas scrubbing
and, in some cases, particulate filtration.
The fuel process reactors manage the gas
feed using a pH control loop, assuring that
the right amount of carbon is provided to
the reactor at all times.
This CO2-to-fuel production platform
synergistically integrates with a clinker
plant to increase profits. Optimum
feed conditions and a state-of-the-art
production system work to produce fuels.
For cement manufacturers, this
represents an opportunity to convert
waste CO2 streams to profits, and to
help turn a global CO2 issue into a
global fuel solution.
The way ahead
Currently the technology is operating at
demonstration scale in Hobbs, New Mexico, USA. At full-scale commercialisation,
this platform ultimately has the potential
to produce up to 94,635l of ethanol or
56,781l of diesel per acre annually, for
around US$0.32/l (US$1.20/gallon) or
US$50/barrel.
“At present, the major objectives in
Hobbs are to demonstrate operational
robustness and steady progress towards
key parameters (eg productivity) that will
ultimately form the ‘blueprint’ for our first
commercial plants. Upon commercial rollout, our intention is to keep the Hobbs
plant running as a valuable platform
for outdoor testing and for on-going
optimisation of our technology,” says
David St Angelo, senior vice president of
engineering at Joule.
And after Hobbs? “The learning from
Hobbs is being applied to the design of
our first commercial plants. The production
unit operating in Hobbs is the fundamental
building block for scaling. As validated by
international Engineering, Procurement
& Construction (EPC) firms, these units
will scale to a multi-acre ‘production
train,’ which will serve as the module for
scaling to a commercial size of 1000 acres
or more. In addition to advancing our
technology and commercial plant design,
we are actively seeking partners – such
as CO2-emitting cement manufacturers –
with whom to build our first commercial
plants. We have already identified many
suitable sites around the world with access
to the resources we need: waste CO2, high
solar insolation, non-arable land and nonpotable water,” David adds.
For cement manufacturers, this
represents an opportunity to convert
waste CO2 streams to profits, and to help
turn a global CO2 issue into a global fuel
solution. Generally speaking, cement
manufacturers have been receptive to the
idea of converting their CO2 emissions
to fuels, along with the opportunity to
market ‘green cement’ and create a new
income stream. David concludes: “As we
progress beyond the demonstration stage
and get closer to commercial production,
we believe there will be even greater
interest.”
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MAY 2014 INTERNATIONAL CEMENT REVIEW