Carbon Capture and Sequestration

Different Types of Carbon Capture

There are several different approaches to carbon capture and sequestration:

• Artificially converting CO₂ in effluent gasses from industrial processes where concentrations are as much as 20%.
• Artificially converting CO₂ from the air at 420ppm or higher - Direct Air Capture
• Biochemically converting CO₂ in the air at 420 ppm or higher with reforestation, afforestation, regenerative farming and soil management via photosynthesis, see Land Based Solutions

A positive report from Imperial College, London speaks to the growth of carbon capture and storage, and its contribution to meeting the necessary goals. Storage projections in Gt are less than previously estimated if we act soon:

"World can likely capture and store enough carbon dioxide to meet climate targets" phys.org - May 20, 2020

Once carbon (as CO₂) is captured, the question is what to do with it next. In addition to storing an enriched stream of CO₂ there are some alternatives, such as methanation with green hydrogen in the Power-to-Gas process. Use of the gas to enhance oil and gas well production is decidedly not recommended since there are risks that the CO₂ may return to the atmosphere in addition to the need to transition away from fossil fuels in the first place.

Problems with Capturing CO₂ from Air

Capturing carbon directly from the air is problematic because the concentration from a processing standpoint is so low, over 420ppm. Natural biological processes, photosynthesis and trees may be a better way than trying to do it artificially.

Why carbon capture might be an illusion, see:

"The Carbon Capture (NETs) Big Lie, Carbon Capture Reduction Calculations Now Being Used to Set Global Fossil Fuel Reduction Targets Will Save Us From Extinction --- Just in Time" - JobOneForHumanity

"New carbon dioxide capture technology is not the magic bullet against climate change" - Phys.org - April 18, 2019

"Study Casts Doubt on Carbon Capture" - Phys.org - Taylor Kubota - October 25, 2019

Artificial Carbon Capture Technologies

Geologic Sequestration of Carbon Dioxide in Class VI Wells

Per the EPA website "Class VI - Wells used for Geologic Sequestration of Carbon Dioxide", "Geologic Sequestration is the process of injecting carbon dioxide, captured from an industrial (e.g., steel and cement production) or energy-related source (e.g., a power plant or natural gas processing facility), into deep subsurface rock formations for long-term storage. This is part of a process frequently referred to as “carbon capture and storage” or CCS.

"Underground injection of CO₂ for purposes such as enhanced oil recovery (EOR) and enhanced gas recovery (EGR) is a long-standing practice. CO₂ injection specifically for GS involves different technical issues and potentially much larger volumes of CO₂ and larger scale projects than in the past.

"Class VI wells are used to inject carbon dioxide (CO₂) into deep rock formations. This long-term underground storage is called geologic sequestration (GS). Geologic sequestration refers to technologies to reduce CO₂ emissions to the atmosphere and mitigate climate change.

For more discussion on Class VI Wells see:

EPA’s Class VI Well Program Key to Deploying CO2 Geologic Storage - Great Plains Institute - Feb 2022

We believe Class VI wells allow storage of CO₂ in salt domes and other 'saline formations' and excludes the use of wells to chemically lock CO₂ as described in the next section.

Geological Sequestration

Geological Sequestration, sometimes known as Carbon Mineral Sequestration, is the step after 'carbon capture' where CO₂ has been separated or concentrated from a waste stream and is pumped underground into suitable geological strata that stores the gas or a solution of the CO₂ gas by reacting it with minerals to form solid carbonates.

For details on water usage as part of the process for carbon capture and sequestration, especially in deep injection wells, there is a wealth of information in a report published by the National Institute of Health library:

"Water Challenges for Geologic Carbon Capture and Sequestration" - NREL/LLNL - February 2010

As reported by BBC Future Planet at:

How Iceland is undoing carbon emissions for good - BBC - July 16, 2020

At aluminium smelters, CO₂ is normally released to the atmosphere. At the smelter in Iceland, CO₂ is captured, dissolved in water and injected into the black basalt rock that the volcanic island is famous for. CO₂ dissolved in water prior to or during injection into the porous basalt rock reacts with the rock formations at a depth of about 500m, where it can turn rapidly into minerals. At Hellisheiði, it takes about two years for 95% of the CO₂ to be mineralised. The process can take more or less time at other sites, depending on a few factors. One is the depth at which the carbon is injected, and another is the temperature of the rock formation – the rate of the mineralisation process is generally faster at higher temperatures.

Carbon Dioxide Underground Storage

In conventional carbon capture and storage, recovered CO₂ can be injected at high pressure into sedimentary basins in a gaseous, liquid or supercritical phase (where the liquid is at a temperature and pressure beyond the point it usually turns into a gas). An impermeable cap rock ordinarily prevents the CO₂ from leaking back to the surface though many see this as a major risk.

Solar Thermal Electrochemical Photo Process

Perhaps there’s hope yet with the Solar Thermal Electrochemical Photo (STEP) carbon capture Process (George Washington University, 2010):

"Solar-powered process could decrease carbon dioxide to pre-industrial levels in 10 years" - Phys.org - Lisa Zyga - July 22, 2010

Similarly for CO₂ to Carbon Nanotubes emerging technology (George Washington University, 2015) see:

"Carbon Capture & Solar Research" - Licht Research Group

and see:

"‘Diamonds from the sky’ approach turns CO2 into valuable products" ACS - August 19, 2015

Metal Oxide Frameworks

Metal Oxide Frameworks (MOF) can reportedly capture CO₂ directly, see:

"Metal–Organic Framework-Based Materials for Energy Conversion and Storage" - ACS - Tianjie Qiu - January 8, 2020.

"New breakthrough in nanotechnology that uses atmospheric carbon to make useful chemicals" - Phys.org - Matt Cichowicz - October 3, 2018

The process requires a source of hydrogen gas. There remain lots of questions since this is still an area of research. Some progress from 2020:

"New technique to capture carbon dioxide could greatly reduce power plant greenhouse gases" - Phys org - Univ. Berkley - July 23, 2020

Cerium Catalyst Conversion to CO

An electrolysis process using a cerium oxide electrode selectively produces CO without the inconvenience of solid carbon. From phys.org, “New route to carbon-neutral fuels from carbon dioxide discovered”, Sept 16, 2019 at:

"New route to carbon-neutral fuels from carbon dioxide discovered" - Phys.org - Stanford University - September 16, 2019

Electrochemical Processes

The technique, based on passing air through a stack of charged electrochemical plates, is described in a new paper in the journal Energy and Environmental Science, by MIT postdoc Sahag Voskian, who developed the work during his PhD, and T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering and reported at:

"MIT engineers develop a new way to remove carbon dioxide from air" - MIT News - David Chandler - October 24, 2019

For a PBSNewshour discussion on the technology see:

"This new ‘battery’ aims to spark a carbon capture revolution" - PBS Newshour - Nsikan Akpan - November 15, 2019

While the process (still in the lab) removes CO₂ from the air and can provide a pure stream of CO₂, that CO₂ has to be stored and disposed of.

Zeolite Processes

A “new material is a bio-based hybrid foam infused with a high amount of CO₂-adsorbing 'zeolites," microporous aluminosilicates. This material has been shown to have very promising properties. The porous, open structure of the material gives it a great ability to adsorb the carbon dioxide” from:

"A sustainable new material for carbon dioxide capture" - Phys.org - Chalmers University of Technology - December 9, 2019

Polymer Membrane Processes

A polymer membrane that enhances the separation of CO₂ in effluent gases is described in:

"A Surprising Substance May Be Key in Capturing CO2 in the Atmosphere" - Norewegian University of Science and Technology - December 11, 2019

Artificial Photosynthesis

Researchers have developed a standalone device that converts sunlight, carbon dioxide, and water into a "carbon-neutral fuel", actually formic acid, without requiring any additional components or electricity. Formic acid is an organic molecule that can be used as a raw material for other organic compounds. It might have the advantage of backing our fossil-fuel based formic acid production. Formic acid in itself is a useful product as a preservative in agriculture. [Note as reported "converted to hydrogen" is not chemically possible.]

"Artificial Photosynthesis Advance: Standalone Device Converts Sunlight, CO2 and Water Into Clean Fuel" - ScienceTechDaily - August 24, 2020