Carbon Dioxide and the Green Gases Agenda

By Sam A. Rushing, President, Advanced Cryogenics, Ltd.
Special to The Digest

Carbon dioxide is generally thought of by those who are not in the gases industries as either a greenhouse gas; and/or for use in beverage carbonation, and perhaps fire abatement.

To those in the gases industries, carbon dioxide is known for much more; including growth in green applications. Beyond the above – mentioned subjects, are numerous applications, which approach 40% of merchant market use, in various forms of food processing; then other major uses including metallurgical applications, Ph reduction, chemical feedstock use, and dry ice pressing, to begin with.

What has become particularly interesting today, and the focus of this article, are ‘green’ applications for the product. This can include uses from agricultural in nature, such as commercial closed greenhouse CO2 enrichment uses, to an ingredient in the growth of algae, which is a form of carbon sequestration; and grain fumigation uses. Other green apps include sequestration of the gas in pre – cast concrete, downhole applications for enhanced oil recovery (EOR), and enhanced coal bed methane projects. Further uses can include dry ice (rice sized pellet) blast cleaning applications, and supercritical extraction technologies. Further to this subject, efforts to commercialize the use of CO2 in plastics manufacturing, and proprietary uses in the manufacture of carbon based fuels such as methanol, ethanol and diesel from the catalyst based conversion of CO2 to CO. Further, developments toward the production of plastics, polymers, and intermediate chemicals from waste CO2 treated with proprietary catalysts have been underway. Other such laboratory claims and successes have occurred, which some claim will be commercialized, and scaled up in the future. In the end, some of this will lead to a reduction of CO2 emissions even before they enter the realm of merchant CO2 supplies. All of this is good for the planet and our health.

GREEN APPLICATIONS – MORE SPECIFICALLY

Some of the ‘green’ applications of carbon dioxide have been around for some time, however, at one time, not thought of as environmentally friendly, per se. These older applications include greenhouse growth enhancement, certain chemical feedstock uses, and dry ice blasting (when comparing with a messy solvent or sand application for the same use); and enhanced oil and coal gas seam recovery of CO2 via replacement of, or trapping CO2 molecules downhole. To further these and more applications, here is more information.

1. Enhanced oil and coal bed methane recovery – This application, particularly EOR is popular, well proven, and is highly sensitive to the price of oil; and for enhanced coal bed methane (CBM), of course this is sensitive to natural gas prices. Today, with an abundance of oil and natural gas, with relatively low or cheap prices for these commodities, many of these projects will move along with greater emphasis and economic success, once the prices for oil and gas rise, and stabilize at a high price. It is said $60/barrel or more is needed for EOR to succeed; given a huge capital investment needed to bring these projects forward. Simply put, with CBM projects, carbon dioxide replaces the methane molecules trapped in coal seams, as the application goes; then with EOR, the CO2 also acts as a weak carbonic acid, dissolving some carbonates and acting as a means of reducing the viscosity of oil, and reducing the swelling of clay in various formations. CO2 in EOR is well proven, and such CO2 floods can run decades – long.
2. CO2 as a solvent – This can include supercritical extraction of essential oils from plant sources, and other substances under pressure. Another interesting application is replacement of perc with CO2 in dry cleaning of fabrics. Some communities have absolutely embraced dry cleaning of fabrics with CO2 v. perc. In both cases, there are health benefits with CO2, in this context, essentially benign v. halogenated hydrocarbons with perc usage in dry cleaning, and hydrocarbon based solvents in some cases of supercritical extraction. When thinking of a solvent, in both applications, the result is excellent when using CO2 v. hydrocarbons.
3. Photosynthesis enhancement – In the case of sealed greenhouse atmosphere enrichment, when taking an ambient CO2 content of about 340 ppm (up to 400 ppm today is possible) to 500 ppm, will increase growth by 15-25%; then when taking this ambient CO2 level to 700 ppm, this can yield plant growth increases by 30-40%. This can replace combusting fossil fuels, for flue gas borne CO2 enrichment, much weaker, and less effective, and limit producing more greenhouse gases let to the atmosphere; this is a further green advantage of using merchant CO2.

Then, the case of algae uptake of CO2 from various sources, including merchant provided product, the CO2 also enhances photosynthesis, thus improves algae growth; thus, for the commercial algae operation, this is an excellent carbon sink particularly when feeding the CO2 from an otherwise airborne CO2 stream; and a means of providing service to the biofuels sector, being green by definition. While larger commercial algae farms are often conceptual at this time, the potential remains strong.

4. Insect control – With respect to grain fumigation, CO2 has replaced rather nasty agents such as carbon tetrachloride, and like agents with great success. In my past experience, most of the structures which held the grain, could be sealed during the fumigation process. The application is green, since hydrocarbons are not used in the process. The CO2 atmospheric content is raised to 60%, and exposure ranges from a day to 60 days, depending upon grain temperatures. The CO2 is vaporized from bulk liquid storage, and applied at the bottom of the silo or storage unit. The results are excellent, and there is no chemical residue on the grain, thus another green benefit.
5. Ph reduction of treated water and process streams – CO2 is commonly used in Ph reduction applications, particularly in many regions of the US where lime softening is used, and the Ph is high. Further to this application, it is also used in various industrial applications, such as the neutralization of alkaline streams, and much more. The benefit is a by-product, in many cases, representing harmless carbonates and by-carbonates; v. sulfates with mineral acids such as sulfuric. Once again, the reduction of nasty by-products, which are difficult to put into solution, such as the sulfates, and harmless constituents left in a potable water stream are found in this process via CO2 application. The application is environmentally friendly and resulting in often safer working conditions, limiting the use of mineral acids.
6. CO2 blast cleaning and insect control – Blast cleaning is a popular method of reducing spillage of solvents which could otherwise be used in the process, including copious amounts of water with or without a solvent; as well as the mess sand blasting leaves behind. This is a relative clean and care – free method of cleaning a wide variety of surfaces, using 1/8” ‘rice’ sized pellets, under pressure; over 80 psig, @ an average 150 cu ft/min flow for many blasting machines. The results are excellent.
7. Sequestration targets – By many definitions, targets or markets such as pre-cast concrete uptake, EOR and CBM downhole, photosynthesis enhancement, and proposed CO2 conversion technologies to CO then to the manufacture of fuels, all represent a form of sequestration; otherwise, largely taking CO2 ‘off the table’, or reducing emissions to the atmosphere. Despite today’s apathy surrounding protecting and defending the environment in America today, promoted by the current political administration; on a local, corporate, and state level, efforts to reduce emissions and promote green technologies are ever important, and underway. Beyond sequestering carbon dioxide via some and many more technologies and applications as outlined above, real improvements and benefits occur via these methods. For example, strength and improved carbonate structure is created with CO2 addition to pre – cast concrete. Then, as mentioned earlier, benefits occur with the process in EOR, beyond sequestration, and for the sake of photosynthesis, plant growth improves via the application of CO2. With respect to the gas companies, it would be who of them to implement as many green applications as possible, both for the sake of their annual reports, as well as the environment. As time passes, more green applications will be developed and implemented.

About the author

Sam A. Rushing is president of Advanced Cryogenics, Ltd., and a chemist by background. The company is supported by decades of diverse professional CO2 and cryogenic gas consulting expertise and merchant background. For consulting expertise and all forms of CO2 and cryogenic equipment, please contact the company. Advanced Cryogenics is here to support your projects and add value to your bottom line. Contact Sam at 305 852 2597 or [email protected]