Carbon Dioxide Recycling in the Biofuels Industry," a special Digest report

September 14, 2010 |

By Direct special correspondent Sam A. Rushing

Perhaps the newfound trend with respect to carbon dioxide (CO2) will be various forms of recycling of this greenhouse gas and gas commodity. There has been a great deal of press associated with new start up companies which propose using CO2 from virtually all source types for the production of everything from plastics, to basic chemicals, to renewable fuels. When scaling up the technology from bench or pilot level, it will be necessary to understand the sources available, and make them as strategically advantageous as possible to fit the technologies which are fostering such recycling.

Since CO2 has been shown to be the globe’s worst offender as a greenhouse gas, the very use of this gas in a technology which would foster the production of viable basic chemicals, plastics, and biofuels is probably some of the best news around. The challenge today is the strategic location of any one source, with respect to the production site of these products, as well as the physical state of the CO2 with respect to the process utilizing the carbon dioxide.

CO2 exists in 3 phases, liquid, gaseous, and solid; however the solid form, dry ice, sublimates once it is formed, and sublimation is the transfer of the solid state to a gaseous state, thus not entering a liquid form. As a commercial or merchant gas, the product is transported and sold in bulk as primarily a liquid product, outside of large long term oilfield requirements. On the other hand, it may not be required to liquefy the CO2 for a captive process such as a biofuels or chemical manufacturing operation, but to use the product as a gas, pipeline delivered; again this considers the production and consumption to be relatively close together – unless economics drive another path.

CO2 sources as a by-product – when concentrated from ethanol and various chemical processes, can be worth various sums of money, when sold to industry – depending upon location, purity and quantity. When the carbon dioxide is in the form of flue gas from various forms of combustion, such as the huge sum of power plant and industrial manufacturing and processing; this CO2 presence in flue gas is often low, and the impurities are high – so usually this is not a raw gaseous stream traditionally worth money – however the seller of this generally worthless flue gas may want economic remuneration in one form or another.

So the challenges for supply of CO2 for various forms of recycling generally boil down to carbon dioxide source types, economic value, locations, sizes, and purity requirements.

Acquiring the Carbon Dioxide

Technically, the CO2 may have an economic value ranging from zero to (perhaps) $25/ton in North America, for example. The CO2 will probably not be turned over without any strings attached, since today and even more in the future, something approximating carbon credits, or tax credits for this CO2 may play a role. In addition to the consideration surrounding various usable credits which the supplier may want to claim, would be the cost of the infrastructure for delivery of this gas to a consuming or processing location, and possibly a dollar value for the commodity itself. The infrastructure, assuming the gas will be delivered to nearby points of application could include blowers and/or compressors for transfer of the gas via pipeline, the cost of a pipeline, and the specific apparatus or equipment required at the inlet and discharge ends of this line.

These sources of CO2 may be from concentrated by-product streams such as ethanol; then perhaps over 98 – 99% content CO2. On the other end of the spectrum would be power plant by-product, which conceivably the power companies should be willing and pleased to rid themselves of the flue gas; however, the CO2 content from coal fired plants may, in some cases, be near 14% content – and whether or not the consuming process can use a lower percentage of content as their feedstock with a high level of impurities.

Also, when considering electric utilities, it is inconceivable they will offer this no strings attached. Further, one might assume the point of CO2 application will drive the strategic location of the CO2 source needed. Given the complex nature of sourcing and source types, it is recommended that a full evaluation of CO2 sources, limited by available purity considerations, volumes, and locations would occur, in order to exact which sources may best fit the CO2 consuming project’s need.

In the merchant CO2 industry, this feedstock is of a high content, relatively pure nature, for the most part; and this is usually sold under take – or – pay contracts. If the source has generally real economic value – that usually being a higher concentration and low impurities, and should the CO2 which is directed to the biofuels projects be of a long term nature, the merchant sector is a difficult means of sourcing such projects, since the product (despite already liquefied and purified) may represent a very significant cost factor.

In the end, should the merchant CO2 network be the means by which the biofuels and carbon recycling projects are sourced, then one must consider all of the costs, which include pricing anywhere from perhaps $80 to $200/ton, plus distribution costs ($2/ each way) and the cost of vaporizing the liquid to a gaseous form; plus capital infrastructure. However, in some cases, given the economics of the proprietary renewable energy nature, of a biological (algae) nature; or of a chemical, or biofuels nature; perhaps economics may work with this form of sourcing.

In my best estimation, probably the merchant sector will supply the demo or pilot phases of such projects at best, v. the long term operations. I suspect this is primarily due to pricing, where we will have to look at direct sourcing from the CO2 emitting options.

CO2 Emitting Options – The Direct Source for Biofuels

Some of the proprietary carbon recycling technologies which have received a great deal of press state CO2 is an ingredient, along with components such as organic nutrients, sunlight, and electricity for example; however the carbon content in the CO2 stream is often neglected within this claim. Logically, when producing a further or final product via a chemical or electrochemical process, a stream of the compound or element in question (CO2 in this case) would provide greater process efficiency and end results, as a function of greater purity or content.

This being said, if the pricy alternatives from a merchant gas company do not destroy the economics; it is logical to first seek the direct enhanced CO2 content raw streams, such as, but not limited to those mentioned ahead.

The CO2 emitting options such as highly concentrated by-product from fermentation / ethanol, anhydrous ammonia, ethylene oxide, and natural wells, may be the best and most reliable method of supplying the new biofuels projects, which will otherwise be thought of as carbon recycling – that being using the CO2 molecules to create new plastics, chemicals (i.e. formic acid, methanol, and more); and biodiesel. S

hould the new biofuels projects be able to source directly from the many sources which yield a highly concentrated CO2, such as those mentioned, this would represent a great deal of available carbon and less of the junk content; presumably making available the process in question work more rapidly and efficiently. Once acquiring such sources, generally under a working contract, sometimes take or pay, the product is often metered across the fence, and delivered via pipeline.

The pipelines found in the CO2 industry are generally not carbon steel construction, due to durability; however often the material which deliver the CO2 in many jobs which require purity is HDPE or stainless steel, rated to endure the pressures sought by the project and distance. With respect to the distance where the product can be sent via pipeline, the limitations are probably capital cost and land right of ways, v. the capabilities where a viable pipeline with the necessary booster blower, or compressors will carry the product as far as desired.

The cost of CO2 pipelines in the oil and gas sector has a $1million/mile price tag; this is a reference for such known projects today. However, when scaling down in a biofuels project, this may vary.

In the end, with respect to concentrated sources, the challenges will be essentially the same in terms of strategic location, that being sourcing the CO2 as close to the carbon recycling renewable energy projects as possible; with the advantage of a relatively high content, quality CO2 to work with, thus fostering better results with the product being produced.

When the options for CO2 sourcing are from flue gas recovered from various forms of combustion, such as power projects, this is more complicated in all respects. First, there is the collection of the CO2 flue gas (estimate maybe 10% content in the flue gas in some cases); and this will have to be collected via a series of blowers and a collection system on the recovery end.

Then, there is going to be a pipeline system, and auxiliary compression, blowers, etc, to the point of application. Next, there is the weaker CO2 content to work with, plus all of the constituents often of a toxic and truly dirty nature present in the raw gas. Unless the expensive process equipment is not available to make the CO2 ready for use without the higher content and a myriad of impurities present; assuming higher carbon dioxide content works better in the process, then expensive capital will be necessary for certain process equipment.

So an evaluation of raw CO2 content feedstock will be necessary on a case by case basis, when considering flue gas.

What to Do

When the carbon recycling or biofuels project requires CO2 feedstock, it is recommended that a thorough investigation take place of source types, CO2 content requirement and tolerance for various impurities and non-CO2 compounds in the feedgas.

The sourcing of CO2 today is more complex than in the past, partly due to the future holding hopes and probable likely carbon credits which will be taken by those who are playing a role in carbon emissions reduction in one form or another.

Therefore one party or the other (seller and buyer) will play a role in this carbon credit or tax credit scenario, most likely. Further, these new schemes for carbon recycling in the form of making a useful product as chemicals, biofuels, etc, is relatively new, and the mechanics for implementing these projects will be developed in a unique way from case to case (feedstock selection, capital equipment, process equipment, etc); therefore the standards will probably be highly variable.

It is essential, however, to understand the options available such as those noted in this article, to best exploit the markets for carbon in a manner which best suits the specific project and actual process. This means evaluating and defining all the available options for the carbon supply; directed by the strategic location of the CO2 consuming plant.

The end result, as these projects become reality, they will place a small dent in the massive carbon imbalance found in today’s CO2 output into the atmosphere v. what the planet and environment will tolerate.

About the Author

Sam A. Rushing is a chemist and president of Advanced Cryogenics, Ltd., and a long standing consultant to CO2 projects of all types globally and domestically. The work includes all technical, business, and market – related tasks, dedicated to all traditional and non traditional project types which surround CO2. Phone 305 852 2597, e-mail: [email protected] , web: www.carbondioxideconsultants.com

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