Carbon Dioxide as applied in the merchant markets today, is a versatile and ever growing product, via new applications in industry. Today, this product is primarily a by-product from chemical processes; however, some is recovered from primarily CO2 rich natural underground sources, and from some flue gas sources. The industry as a merchant product is perhaps 20 million metric tons per year in capacity, growing at perhaps 3% per year. The tried and true forms of production, are the predominant forms of sources and will probably continue to be, unless new technologies to yield an affordable product from stack gas and all forms of flue gas are developed.


Anhydrous ammonia
Recovery of CO2 from anhydrous ammonia has long been a world standard, for relatively clean and simple downstream purification and liquefaction, such that it can readily be used in all phases of the CO2 industry. In some developed world markets, including North America, anhydrous ammonia CO2 by-product has become less available for recovery due to closing of such ammonia plants, due to high prices of natural gas, sometimes exceeding $8-10 per million cubic feet; where affordability ends with a natural gas (methane) feedstock near $4-5 per ton. In the case of the US a few years ago, of the total percentage of merchant CO2 sold, about 40% or greater was borne from anhydrous ammonia sources. Today, this number is about 20%. Another factor driving this situation, are mega-sized anhydrous ammonia plants being built in third world countries, often in the Caribbean and Latin America, with low labour and natural gas prices; hence delivered to certain developed countries at prices well below the domestic product.

Ethylene oxide and titanium dioxide
These two chemical by-product sources are relatively small among the greater listing of CO2 source types, accounting for less than 10% of the total source gas found in most developed world markets, and for the US, this would only account for some 6% of that total source gas for the merchant markets. In the case of ethylene oxide, the cost of plants sourced from this by-product require special metallurgical demands, thus driving up the price of production and capital costs. Moreover, by-product contamination was a learning experience by some gas companies, which later experienced expensive retrofit jobs; therefore, it is not the most desirable source today.

Natural underground & geological sources
Under the best conditions (i.e. when high well head pressures exist, with high CO2 purity) these sources can be the cheapest means of producing a viable merchant CO2 for all markets. In many world markets this is a common form of sourcing, relatively inexpensive and usually highly reliable; all since it may be possible to eliminate the front-end feed compression from a standard CO2 plant, as well as considering there is generally no true ‘source plant’ such as in the ammonia industry, which would experience outages, due to feedstock issues, mechanical breakdowns, and other occurrences representing outages.
Simply, when the product is often highly pure, and requiring minimal purification, and when the head pressure is sufficient to eliminate an expensive feed compressor on a CO2 plant, the cost savings in production can be significant. On the other hand, there can be rather difficult and costly requirements for removing various impurities from the raw gas stream, such as various forms of sulphur and heavy hydrocarbons; that additional power and capital costs in more equipment can simply eliminate what savings would be gained by the high pressure advantage. If, on the other hand, such a source would not have high pressure, and would be relatively impure, the desirability for such feedstock could then be rather poor, unless all other options are unavailable. Such high pressure sources can often run from 500 psig to 2,000 psig and beyond, feeding a CO2 plant which has a working pressure between 250 and 350 psig. The feed compression is an integral part of liquefaction and if this is replaced by natural high pressure, versus a chemical by-product plant often running from zero to 10 psig, the end result again is a true economic advantage.

The sources often found initiating from oil refineries are a significant part of the overall merchant CO2 market supply network. This can run somewhere around 25% in many developed countries, and is replacing certain developing world markets versus current day imports or small & expensive’ CO2 combustion plants’ in the developing world. The reformer off-gas is generally a good quality raw source, low with respect to impurities which are expensive or difficult to remove, similar to ammonia by-product. These are also low pressure as they are delivered from the source (zero to 10 psig) and today, in many developed markets, are fairly well exhausted with respect to merchant gas concerns taking the available product.

As a fast growing market, fermentation has a CO2 by-product which is considered a good quality for recovery and purification, if sourced from dry mill, continuous fermentation plants. In some markets, the available ethanol from these plants has a capacity well beyond what the gasoline industry and oil refineries and blenders are able to utilize - in part driven by certain government sponsored mandates and tax incentives. In any event, when sourced from common wheat and corn, this is the method most utilized in some developed markets; and in other parts of the world such as Brazil, sugar cane is the feedstock for fermentation and is abundant. In the future (perhaps more distant than not) the cellulose–sourced ethanol plants will become widely available, when technologies are developed and refined in such a way that the conversion process of materials such as wood are technically and economically competitive with corn-sourced facilities. This type of source can account for over 30% of the total options in the developed world and perhaps much more in some developing markets, such as in certain Latin American markets.

Combustion plants
This is really a niche market, with basically two or three suppliers strictly for this business. This business of making CO2 via combustion of oil, coal, diesel fuel and other hydrocarbon based materials is somewhat obsolete in many world markets, and as mentioned earlier, being replaced by the traditional source, such as an oil refinery facility. The process essentially combusts the carbon rich material, recovers via a solvent process such as that mentioned below for flue gas sourced plants of a larger stature, and then liquefy, purify and store the product. This is very expensive, and often niche, for very small operations.

Flue gas
Accounting for < 5% of the total source material in most markets, and as mentioned with combustion plants, flue gas utilises a solvent process for recovery. The raw CO2 content, on a percentage basis, found in most forms of flue gas range from 2% to 20% by volume; compared to often > 97% in many of the other traditional sources discussed in this article, outside of combustion plants. In summary, flue gas recovery was very popular in some developed markets over a decade ago, when energy law fundamentals subsidized the process, thus making CO2 recovery a viable form of CO2 sourcing to the merchant markets. This subsidising utilised a form of deferred depreciation or other mechanisms, thus not accounting for a very expensive plant versus a plant from any other traditional source type (outside of combustion as well), which represented a total capital to be from 3-10 times the cost of the usual fermentation, ammonia, or reformer operation, for example. These plants are also high energy consuming operations, thus making this a further factor in general affordability.


The majority of CO2 usage in the developed countries would be dedicated to food and beverage usage, with up to 70% of this greater total market demand in the service of cryogenic freezing and other applications such as modified atmosphere packaging, and various temperature reduction requirements in food processing applications. Of this 70% total merchant market usage in food and beverage, approximately 30% would be dedicated to beverage carbonation and the remaining 40% in food processing applications. In theory, when a product is cryogenically frozen, ice crystals form more rapidly and tend to penetrate cellular walls less readily than the slower forms of freezing, like mechanical refrigeration systems which use agents such as anhydrous ammonia and second generation replacements of former CFC products.
When selling a food product which is subject to loss of moisture, hence a loss of weight and further subject to a loss of a quality appearance, cryogenic technologies tend to reduce such losses; and in the end, a better quality product, with more fluid retention is sold, compared to the lesser quality frozen food products. The further gain is speed in processing, this being a fraction of mechanical refrigeration when using CO2 in such processes, usually referred to as ‘IQF’ (individually quick frozen). It is significantly less expensive to develop a cryogenic freezing system from a capital prospective versus a mechanical refrigeration system; however, the refrigerant price when considering CO2 can rise more rapidly than electric power and ammonia recharge requirements; hence the cryogenic system may be limited in a setting with little CO2 market competition. CO2 as a refrigerant often serves as a bridge between the small – medium size freezing operation and the mega – sized mechanical refrigeration system. It is an interesting application in this industry and has been a major factor in CO2 market growth, particularly in the developed world markets.
Other major CO2 markets include applications as a feedstock in chemical manufacturing processes, metallurgical usage molten steel stirring applications, welding gas mix applications, and usage in foundries. Numerous applications for CO2 usage have been described and applied in crop growth enhancement, also there are applications as a grain fumigant – replacing halogenated hydrocarbon materials, often perceived to be carcinogenic.
A significant market for CO2 in pH reduction applications in the form of carbonic acid usage has been developed in municipal water treatment, cooling water pH reduction and industrial uses where agents such as sulphuric acid are more safely replaced in the form of carbonic acid, when using CO2 diffused in water. A sizable market has been developed for applications in natural gas well stimulation; in some markets this can amount to hundreds or even thousands of tons per day in a region with significant natural gas production. CO2 has been used in the supercritical extraction of essential oils, for example; furthermore as a solvent, it is being tested in markets such as the dry cleaning industry. Beyond these merchant applications, there remains an enormously large application in select oil producing regions, for enhanced oil recovery (EOR), specific to the formations, in conjunction with or without other agents, which in turn, yield further oil produced in often exhausted or partly depleted fields. This can be quite large, for example, in Saskatchewan, a pipeline from Dakota Gasification in North Dakota, USA pipelines over 5,000 tpd of CO2 for EOR, and is planned to maximize into these fields up to a 10,000 tpd pipeline capacity.
In the developing world, up to 80% of the total merchant CO2 demand would be found in soft drink & beer carbonation, with some industrial usage to follow.


In this article, I have reviewed CO2 sources and percentage found in usual developed regions, market applications, market sizes as estimated values, a comment on Kyoto, and CO2 process requirements. CO2 as a merchant gas will continue to grow in applications, as well as available by-product. Management of this balance will be a challenge, and greater utilization in the oil and gas industry will help support the global demand for more oil and gas. CO2 is often known by many as a beverage carbonation agent; however, this is only the tip of the iceberg.

Carbon Dioxide process requirements
In summary, for modern CO2 plants, some half dozen skid mounted components are to be preassembled and engineered to fit the needs of the customer. This means a compression skid, refrigeration skid, dryer skid, and evaporative condenser as some of the major skids.
Construction these days for most plants has a lead time of about 9 months. Other requirements would be evaporative condenser(s), liquid on-site storage tanks, scales, and loading equipment; plus rail facilities, if served by rail. This is a bare bones simple outline for some of the main process components found with a CO2 plant; not to include a flue gas recovery plant or a combustion plant. Beyond this would be catalytic oxidation in some cases for further more difficult purification requirements, and often additional sulphur compound treatment equipment. The compressors are now screw type compared with old fashioned reciprocating used for decades until the 1980s.
These plants use a modern PLC programmed in many cases to operate on a low manned schedule, usually unmanned overnight, with a remote computer access option, as needed. The benchmark standard in all developed and developing markets for the beverage industry as established by the ISBT is essentially a very strict standard, and since it is the benchmark, it is suitable, and equal to or better than all other forms of standard chemical purity for this commodity. In the end, most gas companies sell this for all merchant applications, due to a wish not to mix up distribution equipments, thus introducing possible contamination. The exception to this, would be dedicated oil field and gas stimulation market requirements strictly defined for such service, with much less purification and investment, and ultimately operating cost. This lesser standard would also apply to the EOR markets, which can be huge by all standards in the industry.

Kyoto Protocol
The Kyoto Protocol is a particularly challenging goal to achieve worldwide. In the US alone, greenhouse gas emissions would have to be reduced 7% below 1990 levels during the period 2008–2012. In some estimates, the US is already over 10% above 1990 levels. With the current rate of change, this emissions goal will be exceeded by at least 30% by 2016. The challenges and technical capabilities to meet such Kyoto Protocol levels on a worldwide scale are extremely difficult. Today’s efforts in CO2 recovery from flue gas (and specific cases of product utilization in industry) are a step toward achieving such desired goals as the Kyoto Protocol, and other national or regional air emissions reduction mandates. The battle against global warming is a major economic and environmental concern on a world scale; and CO2 is a major component among the greenhouse gases.

About the author
Sam A. Rushing is a chemist, and president of Advanced Cryogenics, Ltd., which is a CO2 consulting firm serving the CO2 and cryogenic industries. Mr Rushing has 30 years in the CO2 chemical industries, some 18 years as a consultant, and 12 years in the merchant gas industry. All forms of consulting services are offered to such projects. He can be contacted as follows:,,
P.O. Box 419, Tavernier,
FL 33070, USA
Telephone: +1 305-852-2597,
Fax: +1 305-852-2598.