Climate benefits vs. burdens: Which products are best suited for
emerging carbon capture technologies?

Date:
August 25, 2021
Source:
University of Michigan
Summary:
Pulling heat-trapping carbon dioxide out of the air and turning
it into useful products, a concept called carbon capture and
utilization, has the potential to offer both environmental and
economic benefits.



FULL STORY ========================================================================== Pulling heat-trapping carbon dioxide out of the air and turning it into
useful products, a concept called carbon capture and utilization, has
the potential to offer both environmental and economic benefits.


==========================================================================
By some optimistic estimates, CCU could generate annual revenues of
more than $800 billion by 2030 while reducing climate-altering carbon
dioxide emissions by up to 15%. Captured CO2could potentially be used
to make concrete and other building materials, fuels, plastics, and
various chemicals and minerals used in industry, agriculture, medicine
and elsewhere.

But which of these products would be most helpful to the climate? Until
now, there has been no comprehensive study comparing the climate benefits
of a full range of potential CCU-derived products.

A new University of Michigan study fills that critical gap by analyzing 20 potential uses of captured carbon dioxide in three categories -- concrete, chemicals and minerals -- and ranking them by climate benefit. Previous
studies showed that using CCU to make products in those three categories
has the potential to consume up to 6.2 gigatons of carbon dioxide annually
by 2050.

The U-M researchers found that only four of the 20 "CCU pathways" they
analyzed -- two that use CO2 to make concrete and two that use it to manufacture chemicals -- have a greater than 50% likelihood of generating
a net climate benefit. A net climate benefit means the emissions avoided
by using CCU technology outweigh the emissions generated while capturing
the CO2 and making the final product.

The study, conducted by researchers from the Center for Sustainable
Systems at U-M's School for Environment and Sustainability and at the
U-M Department of Mechanical Engineering, was published online Aug. 22
in the journal Environmental Science & Technology.

"Decisions to globally scale CCU operations will require guidance
on identifying products that maximize the climate benefits of using
captured CO2," said lead author Dwarak Ravikumar, a former postdoctoral researcher at U-M's Center for Sustainable Systems who is now at the
National Renewable Energy Laboratory.



==========================================================================
"Our rankings will help prioritize R&D strategies toward products
with the greatest climate benefit while avoiding pathways that incur a significant climate burden and that offer little hope for improvement," Ravikumar said.

The new study also showed that, at the present time, electricity produced
from renewable sources such as wind often leads to a greater climate
benefit if it is supplied to the grid to offset fossil fuel emissions,
instead of being used to make CCU products. That will change over time
as fossil fuels are gradually phased out, according to the study authors.

"Currently, there is a greater opportunity to reduce carbon emissions by
using renewable energy sources to displace fossil fuel-based electricity generation than investing in many of the CCU technologies," said study co-author Greg Keoleian, director of the Center for Sustainable Systems.

"This study is important for prioritizing and guiding the future
development and deployment of CCU technologies, particularly as energy
supplies decarbonize," Keoleian said.

In carbon capture and utilization, carbon dioxide gas can either be
pulled from flue gases at facilities such as power plants and cement
factories, or it can be removed from the ambient air through a process
called direct air capture. In the U-M study, the carbon dioxide is
assumed to have been captured from a natural gas power plant.



==========================================================================
In their study, the U-M researchers determined the lifecycle carbon
dioxide footprints of the materials and energy needed to make the CCU
products, then compared those values to the materials and energy needed
to make conventional versions of those products. They developed a climate return on investment metric to rank and prioritize the CCU products.

The four CCU pathways with a higher than 50% likelihood of generating a
net climate benefit included two methods that use carbon dioxide to mix concrete, one method to produce formic acid through the hydrogenation
of carbon dioxide, and one method to make carbon monoxide from methane.

Formic acid is used as a preservative and an antibacterial agent in
livestock feed and is used to tan leather and to dye textiles. Carbon
monoxide is used in various industrial processes including synthetic
chemical manufacturing and metallurgy.

"While we highlight four technologies, many of the others addressed
in our study will provide a climate benefit under the right boundary
conditions and will generate the products we need. It's just that the
options to achieve these benefits are more restricted. In this study,
that is expressed as the likelihood of a climate benefit," said study
co-author Volker Sick, a U- M professor of mechanical engineering and
director of the Global CO2Initiative.

CCU is distinct from carbon capture and sequestration (CCS), which
involves sucking up carbon dioxide and burying it underground.

The other author of the Environmental Science & Technology paper is
Shelie Miller of the Center for Sustainable Systems, a professor at the
School for Environment and Sustainability and director of U-M's Program
in the Environment.

The research was supported by the U-M-based Global CO2Initiative,
the Center for Sustainable Systems, the School for Environment
and Sustainability, and the Blue Sky Program at the U-M College of
Engineering. The mission of the U-M- based Global CO2Initiative is to get carbon capture and utilization recognized and implemented as a mainstream climate solution.

========================================================================== Story Source: Materials provided by University_of_Michigan. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Dwarakanath Ravikumar, Gregory A. Keoleian, Shelie A. Miller, Volker
Sick. Assessing the Relative Climate Impact of Carbon Utilization
for Concrete, Chemical, and Mineral Production. Environmental
Science & Technology, 2021; DOI: 10.1021/acs.est.1c01109 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210825113659.htm

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