FAQ's - Regarding Arkenol's Technology |
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The Arkenol process, protected by national and international patents, uses concentrated sulfuric acid to convert the cellulose and hemicellulose fractions of biomass into fermentable sugars in an efficient and cost effective manner. For the first time since the petroleum boom, renewable biomass can again become a major source of chemicals for industry and society.
All plant structures are composed of many-linked chains of sugar, cellulose and hemicellulose, which are surrounded by lignin; a glue-like carbon molecule that holds these sugar polymers together. In the first step of the Arkenol process, concentrated sulfuric acid is used to attack the long chain cellulose and hemicellulose molecules, breaking the links of the chain into their simple sugar components. This decrystallization and hydrolysis occurs at relatively low temperatures and pressures. The resulting solution now contains sugar, sulfuric acid, water, and lignin (an inert solid). The lignin is separated from this acidic solution using a filter press. The acidic sugar solution then continues on to a chromotographic separation unit which effectively separates the acid and sugar solution into a pure sugar stream and a pure acid stream. The acid stream, now dilute, is recycled and reconcentrated for further use. The now slightly acidic sugar stream (the separation of the streams approaches 100%) is neutralized with lime; forming gypsum. The gypsum is filtered from the neutralized sugar solution which is sent on for fermentation to the myriad of possible products.
This explanation skips certain intermediate steps that provide for improved yields, but serves to illustrate the straight-forward nature of the process. For more detail, see our Technology section.
By weight, the largest component of plant matter is lignocellulosic material; a mixture of cellulose, hemicellulose, and lignin. Both cellulose and hemi-cellulose are long chain polymers made up of individual sugar molecules. When these long chains are attacked through either acid or enzymatic hydrolysis back to their constituent sugars, the cellulose chain splits into glucose (a six carbon sugar, hence "C6") and hemi-cellulose breaks down into xylose (a five carbon sugar, hence, "C5"). Though cellulose is found in greater proportions than hemi-cellulose, the relative amounts of each within a plant depend upon the kind of plant and its age. In general, hemi-cellulose comprises about 20% of a lignocellulosic material. Many other commercial fermentation methods ignore this valuable fraction.
Compared to hemicellulose, cellulose is a stable molecule that is difficult to hydrolyze. This difference in stability manifests itself in different reaction rates and different reaction end points. Because hydrolysis reactions of cellulose and hemi-cellulose proceed at different rates, care must be taken to maximize yields and recover the resulting sugars prior to degradation to elemental carbon. This process control is central to Arkenol's patents.
In order to utilize the hemicellulosic component of biomass, a viable method of metabolizing the resulting C5 sugars is needed. Techniques ranging from genetic engineering of yeast and bacteria to environmental acclimation are used to develop strains to make use of the hemicellulose. Arkenol has developed a yeast which, through the process a natural selection, has been bred to preferentially metabolize C5 sugars for the production of ethanol. When the C5 sugars have been consumed, the yeast will then metabolize the remaining C6 sugars. This results in increased product yields over competing processes.
The Arkenol process has been consciously designed to be "zero-discharge" from a process view. This means that, to the extent possible, the Arkenol process recovers and recycles all reagents used to effect the hydrolysis of cellulose. Virtually everything that comes into the plant as feedstock leaves the plant as valuable output product. However, as with any process that handles biomass, there are certain "fugitive" particulate emissions. In the Arkenol process, these types of emissions are extremely limited and of no significant consequence.
Numerous independent reviews confirm the soundness of the science which defines the technical approach. The authors range from independent engineers and consultants, such as Arthur D. Little, R.W. Beck, and Purdue University (for the USDA), to in-house reviews by Babcock & Wilcox and Tenneco Energy, and to ethanol plant design engineers including, Lockwood Greene, Zurn/NEPCO, and Raphael Katzen Associates International. Arkenol's proprietary improvements have been protected via various patents, patent applications and trade secrets.
Process economics. Arkenol's founders have directed their engineers to follow the "dumb iron" approach to pilot plant construction and operation and full scale engineering. With recourse to only private funds, Arkenol labored to contain costs through benchtop research to pilot plant construction. This was possible because the focus was not on developing new technology but on identifying and correcting the economic deficiencies of a proven process - concentrated acid hydrolysis.
Arkenol's improvements to overall process efficiencies have resulted in higher concentrations of sugar and acid which require less energy to ferment and distill and reconcentrate for reuse. Arkenol's process improvements have also resulted in higher sugar yields per cellulose unit further enhancing process economics.
Of lesser importance, perhaps, is Arkenol's selection of the concentrated acid hydrolysis process which provides higher tolerance for variations in feedstock compositions. Genetically enhanced organisms used in simultaneous saccharification and fermentation processes are less robust and prone to destruction due to the required mechanical handling of the pumping processes used in continuous fermentations. For instance, these organisms are affected by co-factors present in feedstocks like municipal solid waste that, without pre-processing, result in the inhibition or even destruction of the organisms used. Concentrated sulfuric acid is an effective screening agent for these co-factors.
To summarize, Arkenol's scientific and process improvements are described as follows:
It is useful to note that unlike hydrochloric and hydrofluoric acids used in competing processes, sulfuric acid is not toxic.
Absolutely not. Odor control has been a criteria around which the biorefineries have been designed. It is clear that any odors associated with Arkenol's feedstocks and with feedstock handling have been managed by other processes to the extent necessary for community acceptance. Odors associated with products and co-products are also considered innocuous.
Through an arrangement with an EPC contractor and engineering firm, Arkenol can provide financeable process guarantees backed by the strength of the Arkenol corporate project team members.
The cost of the process depends upon the selected feedstock, the amount of processing required for that feedstock, and the products which are produced. The effective capital cost of a biomass to ethanol facility is today about $5.00 per installed gallon of annual capacity. Our engineers continue to work with materials of construction, process improvements, and process design to achieve a lower targeted installed cost of $3.00 per gallon.
While this compares to corn-to-ethanol technology at around $2.00 per installed gallon, a correct comparison of costs must include feedstock. Today, corn sells on the spot market at more than $4.50 per bushel, or $160 per ton. Almost any of Arkenol's feedstocks are available at $20 per ton or less, and in some cases, Arkenol will be paid to take and process certain waste streams. It is this vast difference in feedstock costs that helps makes the Arkenol process viable.
Send us your financial statements and we'll provide more detail!
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