Carbon Capture: Possible Solutions, Pt. III

Capture Without a Cave
Several companies are proposing ways to capture carbon without the geological engineering and policy headaches that come with underground storage. Some of the leading ideas include:

A. Mineralization
Carbon dioxide can be stored by turning it into stable carbonate mineral. This is made through a chemical process that actually speeds up a natural process that changes the CO2 gas into a solid mass. When it's done in nature the CO2 turns into limestone. When higher temperatures or pre-treatment of the minerals speeds up the process, the result is CO2 in solid form, not dependent on sealed storage space below ground or sea level. Though the technology is estimated to use much more energy than a regular power plant.

Carbon Sciences has a system for converting CO2 into calcium carbonate (CaCO3). Calcium carbonates can sell for $1,000 a ton and the paper industry, which started substituting it for wood chips in the 1980s, buys 80 percent of it. Converting gases into a solid requires energy and money, but the energy usage and cost are offset because the calcium carbonate won't have to be mined from the ground.

The process of mineralization can also be used in building products. CalStar is a company that takes advantage of this technology when making bricks for buildings. Instead of burning clay, CalStar takes fly ash, the particulate matter that ordinarily leaves smokestacks to enter the atmosphere, add some extra chemicals and make bricks. Rather than requiring high temperature cooking, the chemicals sort of congeal into a solid, hard mass. The CalStar process will reduce the energy content in bricks by over 90 percent, according to CalStar.

Another actor in this field is Skyonic. Its SkyMine process is a post-combustion technology that fits with large CO2 emitters like coal, natural gas or oil fired power plants. The process is said to remove CO2 from conditioned at-temperature flue gas and store it as stable sodium bicarbonate (industrial clean baking soda). It also returns the flue gas to the plants stack for release.

B. Algae
CO2 can be turned into food for algae, which then can be used to make biofuel. Algae are also fast-growing and harness sunlight and CO2. Some researchers believe they can use the stored energy within the algae and convert into fuels such as biodiesel and ethanol. Also, proteins produced by algae could be used for animal feed.

The method has not been tested on a big scale. However, startups like SequesCO claim it is possible.

C. Untouched Rain Forests
Rain forests act as a carbon sink when it comes to taking care of greenhouse gases, and there is more carbon stored in the world's forests than in all remaining oil reserves in the world. That shows the importance of keeping the forests alive. Young, actively growing forests consumes more CO2 than it releases and could be used for lowering the effects of CO2 emissions.

Forestation carbon credits are already for sale on auctions and carbon markets conducted by WorldEnergy and others.

Countries in the Rainforest Coalition, like Papua New Guinea, Brazil and Costa Rica, are somewhat dependent on the destruction of the forests for their economic growth. In the same time, the rest of the world is dependent on the preservation of the forests' natural wealth. The Rainforest Coalition recognizes this and their solution is putting a price on the action of not harvesting the forests and controlling the logging.

"The objective, is to align the interests of rain forested developing nations with industrial nations – with the latter offering markets for carbon off-sets and forest products," said Sir Michael Somare, the Prime Minister of Papua New Guinea, in an interview with The Independent. "If we, the rain forested nations, reduce our greenhouse gas emissions, we should be compensated for these reductions, as are industrialized nations. It's that simple."

D. CO2 Into Fuel
Carbon Sciences says it has the technology to transform CO2 into basic fuel building blocks. It converts CO2 into hydrocarbons (methane, ethane and propane), which can be used for gasoline and jet fuel.

It is a biocatalyst process, which means that both microbes and chemical catalysts are involved. The biocatalysts "destabilize" the carbon dioxide. Water is injected as part of the process. The end result is a number of carbon-hydrogen molecules, which become precursors to fuel. The hydrogen atoms released from the water molecules do not have to be converted into freestanding hydrogen molecules in the company's process. The biological part of the process is key because CO2 is a stable molecule; cracking or destabilizing it requires quite a bit of energy with traditional processes.

Carbon Sciences isn't the first company to think of something like this. LanzaTech, a Khosla Ventures company, wants to make ethanol from CO2. Japan's Mitsui is also trying to turn carbon dioxide into methanol, another liquid fuel.

Also, Scientists in Singapore say they've found a way to turn carbon dioxide into methanol, using less energy and lower temperatures than previous processes. The new process uses N-heterocyclic carbenes (NHCs) as an organocatalyst, then adds hydrosilicane – a combination of silica and hydrogen – and water to make methanol, according to a study published in the journal Angewandte Chemie International Edition.

But don't hold your breath. "There is a good reason CO2 is the end product of combustion. It is a low energy molecule," said Steve Koonin, the former BP chief scientist who is now in the Department of Energy." Getting rid of CO2 by burying it underground may be the best option.