Tech Briefs Magazine - October 2023 - 39

Sustainable Technology
Turning Carbon Emissions into Rocks
A technology repurposes waste from industrial mines by storing carbon pulled from the
atmosphere into newly formed rock.
University of Pennsylvania, Philadelphia, PA
I
n Penn's Clean Energy Conversions
Lab, researcher Peter Psarras and colleagues
are repurposing waste from industrial
mines, storing carbon pulled
from the atmosphere into newly formed
rock. The team sees great environmental
potential in mine tailings, the sand and
sludge left behind after the sought-after
ore gets removed. With samples in the
lab, they're trying to determine just how
much calcium and magnesium each contains,
how to best carbonate it with CO2,
how and where they can store the result,
and whether the process is scalable.
At the highest level, these researchers
are shepherding the material from its
starting point - rock at the mine - to
a sand-like substance, then into a solution,
and back to rock. Many intricate
steps in between begin by scrutinizing
the original material.
" When we receive the tailings, we first
test for a couple things. We look for inorganic
carbon, so are the tailings taking
CO2 out of the air naturally? We
don't expect that to happen, but we
want a baseline of what carbon was already
in there, " Psarras said. They also
check the rock's size, to determine
whether they'll have to grind it down to
the tiny particles they need, and analyze
its chemical composition, looking for
calcium and magnesium, most importantly,
but also other scarcer metals like
lithium, cobalt, and nickel.
Open-pit mines like the one seen here generate millions of tons of waste each year. Researchers in
the Clean Energy Conversions Lab are working on technologies that could turn this waste into carbon-storing
rocks, potentially keeping a substantial amount of CO2 out of the atmosphere. (Image:
Peter Psarras)
Here, calcium and magnesium matter
most because the process requires alkalinity,
which neutralizes the acidic carbon
in a reaction that stores CO2 in mineral
form. Because the mineral diversity
of tailings changes by site, this is a crucial
set of steps in the process.
Most people understand carbonation
as it relates to fizzy drinks; add carbon
dioxide to water and it becomes seltzer.
In this process, the team adds CO2 to a
pressurized vessel that contains the calcium-
or magnesium-rich liquid they
created in the previous step. That vessel
then goes into a machine that heats and
mixes what's within. The middle product
is a solution and when CO2 is
pumped into it you get a solid. Beyond
Often, industrial mine waste starts as rock, which the researchers then turn into a sand-like substance (left). After analyzing its chemical composition,
they extract calcium and magnesium, creating a solution (center) then put into a pressurized vessel injected with CO2. Finally, the vessel goes into a
machine that heats and mixes what's within (right). (Image: Peter Psarras)
Tech Briefs, October 2023
www.techbriefs.com
39

http://www.techbriefs.com

Tech Briefs Magazine - October 2023

Table of Contents for the Digital Edition of Tech Briefs Magazine - October 2023