Ethanol sourced Carbon Dioxide and the Energy Sector

By Sam Rushing, President, ADVANCED CRYOGENICS, LTD.
Special to The Digest

In the U.S., ethanol by-product carbon dioxide, is a dominant form of CO2 off-gas from all CO2 processes and source types; and this carbon dioxide is significant in the supply to energy – related projects. This (fossil fuel) energy related sector will remain in high demand, even though the long term answer to the global energy demand, will have to be fulfilled via renewable sources, with a great deal of reliance on biofuels. This piece describes the application of CO2 in the enhanced production of primarily fossil fuels. Despite today’s dip in oil and gas prices, the application of CO2 in all sectors described below will grow even stronger, as the availability of fossil fuels are depleted over time. The sale of CO2 from the ethanol industry is an outstanding opportunity for enhancement of the overall fermentation project’s revenues, and whether or not the revenues from the sale of ethanol alone are rich or not; it is ever important to maximize the yield from the sale of by-products to viable markets. The opportunities for the sale of CO2 within specific markets must be properly evaluated, in order to produce the best results.

The uranium sector is returning since nuclear plants will be built on a greater schedule, and CO2 is a feedstock used for in-situ leaching, or solution mining of uranium; and of course the production of oil and gas are highly integrated into various CO2 applications for enhanced and improved recovery techniques.

With respect to ethanol, over time, the torch has not successfully been passed from corn – based fermentation projects to second generation ethanol projects; thus removing the food and famine misconceptions. As the development of second generation ethanol moves forward, the carbon dioxide by-product will of course have opportunities in the energy sector as well.

Within the last two years, I worked with an energy firm, Hartree Renewables, which successfully restarted an ethanol plant in West Texas, which is producing 500 TPD of CO2 for EOR. To see such successful projects is gratifying, and relevant to this article.

CARBON DIOXIDE CONSUMED IN THE RECOVERY AND PRODUCTION OF ENERGY – BASED MATERIALS

The major areas of CO2 consumption include a very old technology; but one with long term potential, that being EOR or enhanced oil recovery. Please see image 1 as a basic CO2 sourced EOR diagram. Another old technology, but with little volume domestically,  would be so-called ‘frac’ used in natural gas well stimulation projects. Further, since nuclear power is now on the forefront of interest again, globally, uranium value should rise, precipitating the reopening of uranium mines. In the recovery of uranium via in-situ applications, carbon dioxide is often a feedstock, along with anhydrous ammonia; thus leaching via ammonium carbonate compounds for this application.

Image 1 – Simplified CO2 based EOR image

With the rise in ever-hungry power demands of the AI data centers, nuclear power can be a part of the answer for these requirements; and if not as much in the US, this will be the case in many global markets. Currently, there are 70 GW of new nuclear power developments underway globally; in part, to bridge this gap for cleaner, carbon emission free, forms of power. Some will include the smaller modular reactors in the US, specific to niche demands such as Google’s planned AI data centers.

Demonstrations and tests for CO2 usage in coal seams thus replacing methane molecules with CO2 can both produce natural gas and sequester CO2 – this is enhanced coal bed methane; and back to the 1990s such tests have occurred – some of which were government funded. There is of course, pushback surrounding the potential for methane leakage; however, this form of natural gas production may increasingly be on the radar, with current government interest in fossil fuel production.

A major supplier of natural CO2, from high pressure wells in the US south – central region within and surrounding Mississippi, is the Jackson Dome. This resource for CO2 has been supplying the merchant CO2 market for numerous merchant plants in Mississippi for many years. And over the years, Denbury Energy (now ExxonMobil) the owner of these properties has increasingly directed the CO2 to EOR destinations; and this transition from merchant sales to EOR is driven by the ever more finite life of the CO2 wells. The logical replacement on a large scale, over time, could be biofuels, largely the development of second generation ethanol plants; and utilizing grain based facilities as well. Some time ago, I evaluated various potential cellulosic ethanol ventures in neighboring states; and this sector could help fill the gap for the regional merchant sector. This presents a  significant value – added opportunity for ethanol projects regionally, as they are developed over the term ahead. The value behind these so-called natural CO2 sources were high wellhead pressures, helping eliminate feed compression in a CO2 plant; this resulting in historically cheaper production from the Jackson Dome.

 With respect to EOR, the electric power firms have evaluated EOR as a possible home for their carbon dioxide emissions; however, developing successful cost-effective recovery means (outside of the well proven MEA based projects) are very challenging, plus distribution and horsepower downstream of CO2 recovery are a further cost, but could in part be borne by the oil company seeking the commodity for EOR use. The electric utility sector has a way to go, from technology, cost effective, and strategic location perspectives.

Image 2 Map of primary EOR projects & sources

In the major existing and long lived regions for EOR in the United States, are primarily the Permian Basin (Texas, New Mexico region), served by the New Mexico (CO2) Bravo Dome; the McElmo Dome and Sheep Mountain in Colorado. Also, as mentioned above, Jackson Dome in Mississippi, for regional projects, these projects have primarily been sourced by natural underground CO2 sourcing, with high pressure. These forms of CO2 sourcing have been of very large volume, and have been in place for many years. Today, ethanol projects using grain as a feedstock exist in SW Kansas for  EOR projects in West Texas. EOR projects are also sourced from amine recovery sources  in Wyoming; and the U.S. Dakota Gasification plant is sourcing the large Encana and other Saskatchewan projects with large sums of CO2 delivered by pipeline – however this source going into Saskatchewan are derived from Dakota Gasification in Beulah, ND. More such opportunities from ethanol and other highly concentrated chemical and energy projects will supply this sector of the energy industry. Enhanced oil recovery, can be a huge CO2 market, but the price of the commodity is a fraction of the value in the merchant sector; therefore specific and long term placement is essential to make these projects viable. As to frac, there were large demands used by oilfield service companies such as Halliburton and JB Hughes; and much of this converted to hydraulic fracturing years ago. Today, CO2 fracs seem to have a future in China, among other countries. The advantage with CO2 is a solvent acting as the agent behind fracturing and sweeping the well; v. water in hydraulic fracs which has huge disposal problems associated with the cheaper technology. We may see more CO2 in this application ahead, some of which driven by environmental damage caused by water disposal problems when hydraulically fracturing v. CO2 fracs which are essentially a cleaner, energized fluid; with a higher cost associated with this technology.

SUPERCRITICAL CO2 IN POWER PRODUCTON

We must not forget, supercritical CO2 usage for electric power production, in the form of driving turbines – a unique application, and should expand over time. Ultra efficient turbines are the power producing machines of the future.

Image 3 sCO2 usage in power production

This is how it goes: Supercritical CO2 (sCO2) can turn turbines to generate electric power by replacing steam as the working fluid in closed -loop thermodynamic cycle, offering higher efficiency, more compact equipment; due to CO2’s high density in the supercritical state. In this process, a heat source heats and expands the sCO2, spinning turbine blades connected to a generator – absolutely promising for the increased power output, and smaller components; there are the challenges such as durability of the materials used in the process at high pressures. However, all of this is achievable, and a part of tomorrow’s more efficient power production.

THE FUTURE  

I hope for a future, where environmentally friendly energy projects will  further reduce CO2 emissions from energy projects, such as power plants and advanced biofuels projects. As was mentioned before, the practical cost of recovering lean CO2 streams, such as from gas and coal fired power generation plants must concentrate the CO2 before the product travels the through liquefaction/purification steps; and even today, the options for concentrating this lean raw CO2 gas stream are expensive, or not proven in terms of more economical strategies; where membrane and ammonia refrigeration systems have been proposed; but we do not have any proven technologies other than amine solution methods as the most logical means of achieving these ends. Until better or more efficient means of concentrating the flue gas sourced CO2 can be proven without a doubt, then subsidies, including 45Q and the IRA will be needed to use today’s successful options.

In the past, under prior US energy laws, back to the 1980s – 90s, subsidies of a form existed with cogeneration plants, in the form of a thermal host. The cogenerated steam was used in the amine recovery process; thus the so-called thermal host. Something such as this, perhaps 45Q, in order to make challenging economics work; or new, fully proven technologies will emerge which will then make flue gas recovery of CO2 a viable commercial option for sourcing CO2 to the energy and other sectors. Membrane technologies are a possibility as well, however, on a larger scale, much of this has not gained significant traction, from economics and technical perspectives as of now.

I continue to believe the CO2 from power plants is among the most strategically located source of CO2; that being near large economic and industrial areas, however, we have little CO2 from flue gas projects to represent much value today. In the end, it is all about the most concentrated and hopefully pure forms of CO2 by-product which are being used today for merchant use – and of course this means the cheapest form of production to be found is first sought.

The demand for agents used in all forms of enhanced recovery of natural gas, oil, and coal bed methane projects will probably grow even stronger. The commodity value for oil has always been volatile, driven by too many factors to count. In 2022 the value of oil was over $100/barrel, now it is in the $60s. This value is volatile, as are many other commodity values. I believe the oil producing regions of many nations will continue to squeeze out as much oil as possible from the  largely depleted fields; thus enhanced oil recovery via CO2; and this is even more enticing as ethanol projects (primary and then secondary) become an even greater supplier to this and other energy – related markets such as that described in this article. Longer term potential for CO2 fracs and enhanced CBM exist globally.

CO2 fracs, where the commodity acted as an ‘energized fluid’, v. hydraulic fracturing is essentially not an active part of the oil and gas fracturing industry today; where most of this activity converted from CO2 years ago to hydraulic fracturing; in part due to cost. During this period of CO2 fracs, the laid in price was often around $100-120/ton; where prices today should be higher in regions where this activity occurred, such as the US and Canadian Rockies; and the US Permian Basin, among others. In any event, I believe the longer term potential for ‘cleaner’ and more effective CO2 fracs has a future.

The basis for economic viability in all CO2 sourcing and applications projects in energy related ventures requires strategic location. This is why, even if economically viable flue gas recovery methods for supply to the EOR sector existed, the location would have to remain within a reasonable distance to the point of application. The very large CO2 use for EOR projects will have to be delivered by pipeline v. over the road trucks, rail, or barge. The pipeline option has been the method for EOR supply to large project always, and this is the only means of effectively planning and controlling the cost of delivery.

About the author:

Sam A. Rushing, a chemist, is president of Advanced Cryogenics, Ltd., a global, leading CO2 and cryogenic gas consultant is ready to provide professional services to all aspects of your CO2 project. Services range from business, markets, to technology, process, and technical expertise. The company is supported by over 30 years of CO2 and chemical industry expertise. www.carbondioxideconsultants.com , telephone 305 852 2597,