Chemical Engineering September 2022 - 10

ability to induce biofilm
formation in E. coli. This
screening used a strain
of E. coli (MC4100) that
is widely used to study
genes and proteins and
is known to be poor at
forming biofilms, and
compared it to another
E. coli strain (PHL644),
an isogenic strain obtained
through evolution
that is a good
biofilm former. This
screening revealed the
chemistries that are
best suited to stimulating
biofilm formation.
The researchers then
monitored the biomass
and biocatalytic activity
of both strains incubated
in the presence of these
polymers, and found
that MC4100 matched
and even outperformed
PHL644. Further studies
examined how the
polymers stimulate
these " profound " increases
in activity. ❐
Silicate-rock-based material can replace flyash in
cement, lowering costs and CO2
F
lyash, a waste byproduct from coal
burning, has been used effectively as
a supplementary cementitious material
(SCM) in Portland cement to displace
a portion of the cement and lower the CO2
emissions associated with cement making.
But because coal burning is becoming less
common, supplies of flyash are more limited
and its quality more variable.
The company Terra CO2 (Golden, Colo.;
www.terraco2.com) has developed a process
for making a flyash replacement from silicatebased
igneous rock. The product, known as
Opus SCM, promises to alleviate issues with
flyash supply and lower the costs associated
with transporting flyash for cement making.
Opus SCM can be blended into portland
cement to displace between 10 and 30% of
the cement. Terra CO2 plans to break ground
on the first commercial plant to produce
Opus SCM in late 2023.
Manufacturing Opus SCM involves widely
available, alluvial and granite-based construction
aggregates, which are milled to a
size of 6-7 µm. This size is similar to that of
the limestone used to make portland cement.
The powder is then pneumatically conveyed
to a proprietary reactor, where it undergoes
air-suspension melting. " We suspend the
particles in a flame, " explains Bill Yearsley,
president and CEO of Terra CO2. " It's a dust
cloud at that particle size, so a good portion
of our trade secrets are around what we call
'cloud management.' "
The material " cloud " is melted in milliseconds
inside the reactor, resulting in glassy
particles that are quenched with ambient air.
The resulting reactive microspheres can replace
flyash in concrete formulation.
" The materials we use to make Opus SCM
are widely available at scale, so they don't
require extensive transportation to deliver to
concrete makers, and don't require opening
new mines, " Yearsley points out. The product
would be delivered to a silo at a readymade
concrete site, similar to how flyash is
currently used.
Using the same manufacturing process,
Terra CO2 plans to introduce a blended cementitious
material (BCM) that will be used
with an additive at levels of 40% or higher in
cement, and eventually, a geopolymer that
can be a full replacement for portland cement,
Yearsley says.
n
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Chemical Engineering September 2022

Table of Contents for the Digital Edition of Chemical Engineering September 2022
