InTechOpen uses cookies to offer you the best online experience. By continuing to use our site, you agree to our Privacy Policy.

Engineering » Environmental Engineering » "Biofuels - Status and Perspective", book edited by Krzysztof Biernat, ISBN 978-953-51-2177-0, Published: September 30, 2015 under CC BY 3.0 license. © The Author(s).

# Production and Use of Evolving Corn-Based Fuel Ethanol Coproducts in the U.S.

By Kurt A. Rosentrater
DOI: 10.5772/59951

Article top

## Overview

Figure 1. Corn-based Distillers Dried Grains with Solubles (DDGS) is currently the most common coproduct available from U.S. fuel ethanol plants (Photo courtesy of Rosentrater).

Figure 2. U.S. fuel ethanol (gal) and DDGS (t) production over time; RFS denotes levels mandated by the Renewable Fuel Standard. Inset shows number of U.S. ethanol plants over time [12, 13, 14, 15].

Figure 3. U.S. dry grind corn-to-ethanol manufacturing plants. A. 450 x 106 L/y plant. B. 80 x 106 L/y plant (Photos courtesy of Rosentrater).

Figure 4. U.S. corn production (bu) and consumption according to major categories of use (adapted from [16]).

Figure 5. Flow chart of typical corn dry grind fuel ethanol and coproducts processing operations.

Figure 6. A. DDGS exports from the U.S. over time. B. Countries who imported DDGS from the U.S. in 2008, 2010, 2012 (adapted from [27, 29]).

Figure 7. DDGS sales price over time (monthly averages) (adapted from [16, 30]).

Figure 8. A. Example comparisons of DDGS, soybean meal (SBM), and corn sales prices and their relative comparisons. B. Cost comparisons on a per unit protein basis (adapted from [30]).

Figure 9. Fractionation of DDGS into individual chemical components (or at least concentrating them) offers the opportunity for new value-added uses and new revenue streams.

Figure 10. Oil is now removed at many ethanol plants via centrifugation of condensed distillers solubles, after a heating step and additional chemicals are added, which allow the oil to be removed without forming an emulsion.

Figure 11. Distillers Oil, Feed Grade, is being extracted from nearly 85% of all U.S. ethanol plants in 2014 (Photo courtesy of Rosentrater).

Figure 12. Coproducts will continue to play a key role as the biofuels industry evolves and becomes more fully integrated. This figure illustrates one concept of combining fuel production with animal and plant production systems.

# Production and Use of Evolving Corn-Based Fuel Ethanol Coproducts in the U.S.

Kurt A. Rosentrater1

## 1. Introduction

We face many challenges in our society, due especially to growing population pressures and increased economic mobility. These can result in increased demands for food, clothing, housing, and consumer goods. Additionally, there has been a growing need for energy during the last several decades, which historically has been met primarily by use of fossil fuels. In the U.S., transportation fuels generally account for about 1/3 of all energy consumed. Of this, about 90% comes from fossil sources. Between 1/2 and 2/3 of the total U.S. demand for petroleum has been met by imports during the last 30 years [1]. Many argue that this scenario is not sustainable in the long run, and other energy alternatives are needed. During 2005-2010, the U.S. experienced some of the highest growth rates ever seen in the domestic biofuels industry.

#### Figure 7.

DDGS sales price over time (monthly averages) (adapted from [16, 30]).

#### Figure 8.

A. Example comparisons of DDGS, soybean meal (SBM), and corn sales prices and their relative comparisons. B. Cost comparisons on a per unit protein basis (adapted from [30]).

## 5. Coproduct Evolution

Even though the corn ethanol industry is maturing, there continue to be efforts to develop new, valued-added materials from the corn kernels as well as from the coproduct materials. When these research efforts are commercialised, they will result in more products from the corn kernel itself (an approach known as upstream fractionation) and the distillers grains (known as downstream fractionation). These types of fractionation approaches can result in the separation of components of high, medium, and low value (Figure 9). For example, several mechanical and chemical approaches have been developed to remove protein, fibre, or oil components from the endosperm (which contains the starch). This type of separation will allow a highly-concentrated starch substrate to be introduced to the fermentation process, and will allow the other corn kernel components to be used for human food or other high-value applications. [31] provided an extensive discussion regarding various pre-fermentation fractionation approaches. On the other hand, post-fermentation fractionation techniques have also been examined. For example, [32] used a combination of air classification and sieving to separate fibre particles from DDGS. All of these approaches, if implemented commercially, will alter the chemical composition and digestibility of the resulting DDGS.

Many plants have recently begun adding capabilities to concentrate nutrient streams such as oil, protein, and fibre into specific fractions, which can then be used for targeted markets and specific uses. For example, one company in Iowa is now separating fibre from the DDGS and using it as a feedstock for cellulosic ethanol production. Additionally, many companies have begun removing oil from the whole stillage and/or CDS streams (Figure 10). This oil, which is officially known as Distillers Oil, Feed Grade (Figure 11), can readily be converted into biodiesel or animal feed ingredients, but they cannot be used for food grade corn oil, because they are too degraded. In fact, more than 85% of U.S. ethanol plants are now removing oil, because the economics are so favourable. Of note, in 2010 almost no ethanol plants were extracting oil...the rapid increase has solely been due to added value streams for the ethanol plants. On the horizon is concentrated corn proteins, which can be used for high-value animal feeds (such as aquaculture or pet foods), or other feed applications which require high protein levels (such as monogastrics or younger animals).

#### Figure 9.

Fractionation of DDGS into individual chemical components (or at least concentrating them) offers the opportunity for new value-added uses and new revenue streams.

#### Figure 10.

Oil is now removed at many ethanol plants via centrifugation of condensed distillers solubles, after a heating step and additional chemicals are added, which allow the oil to be removed without forming an emulsion.

#### Figure 11.

Distillers Oil, Feed Grade, is being extracted from nearly 85% of all U.S. ethanol plants in 2014 (Photo courtesy of Rosentrater).

As these process modifications are developed, tested, and implemented at commercial facilities, improvements in coproducts will be realized and increasingly used in the marketplace. These new products will require extensive investigation in order to determine how to optimally use them and to quantify their values in the marketplace.

## 6. Conclusions

The fuel ethanol industry in the U.S. has grown exponentially during the last decade in response to government mandates and due to increased demand for alternative fuels. This has become especially pronounced as the price of gasoline has drastically fluctuated, and consumers have realized that fuel prices are problematic. Additionally, energy has become an issue of national security. Corn-based ethanol is not the entire solution to transportation fuel needs. But it is clearly a key component to addressing energy needs. Corn ethanol is seen by many as a transition to other bio-based fuels in the long run; but this industrial sector will continue to play a key role in the bioeconomy, as it is a proven approach to large-scale industrial bioprocessing. And as the industry grows, coproducts will become increasingly important for economic and environmental sustainability. One way to improve sustainability is to diversify coproducts as well as integrate systems (Figure 12, for example), where materials and energy cycle and recycle. For example, upstream outputs become downstream inputs for various components of a biorefinery factory, animal operation, energy production (i.e., heat, electricity, steam, etc.), feedstock operation, and other systems. A closed loop system would be the ultimate scenario. By integrating these various components, and developing a diversified portfolio (beyond just ethanol and distillers grains) the biorefinery will not only produce fuel, but also fertilizer, feed, food, industrial products, energy, and more importantly, can be self-sustaining.

#### Figure 12.

Coproducts will continue to play a key role as the biofuels industry evolves and becomes more fully integrated. This figure illustrates one concept of combining fuel production with animal and plant production systems.

## List of Abbreviations

CDS: Condensed distillers solubles

DDG: Distillers dried grains

DDGS: Distillers dried grains with solubles

DWG: Distillers wet grains

DWGS: Distillers wet grains with solubles

RFS: Renewable Fuel Standard

SBM: Soybean meal

## References

1 - U.S. EIA. (2011). Annual Energy Review. Energy Information Administration, U.S. Department of Energy: Washington, D.C. Available online: www.eia.doe.gov/emeu/aer/.
2 - Agrawal, R., N. R. Singh, F. H. Ribeiro, and W. N. Delgass. (2007). Sustainable fuel for the transportation sector. Proceedings of the National Academy of Sciences 104(12): 4828-4833.
3 - Alexander, C. and C. Hurt. (2007). Biofuels and their impact on food prices. Bioenergy ID-346-W. Department of Agricultural Economics, Purdue University: West Lafayette, IN.
4 - Cassman, K. G. (2007). Climate change, biofuels, and global food security. Environmental Research Letters 2(011002): DOI # 10.1088/1748-9326/2/1/011002.
5 - Cassman, K. G. and A. J. Liska. (2007). Food and fuel for all: realistic or foolish? Biofuels, Bioproducts and Biorefining 1(1): 18-23.
6 - Cassman, K. G., V. Eidman, and E. Simpson. (2006). Convergence of agriculture and energy: implications for research policy, QTA2006-3. Council for Agricultural Science and Technology: Ames, IA.
7 - Dale, B. E. (2007). Thinking clearly about biofuels: ending the irrelevant ‘net energy’ debate and developing better performance metrics for alternative fuels. Biofuels, Bioproducts, and Biorefining 1: 14-17.
8 - De La Torre Ugarte, D. G., M. E. Walsh, H. Shapouri, and S. P. Slinsky. (2000). The economic impacts of bioenergy crop production on U.S. agriculture, Agricultural Economic Report 816. USDA Office of the Chief Economist, U.S. Department of Agriculture: Washington, D.C.
9 - Dewulf, J., H. Van Langenhove, and B. Van De Velde. (2005). Energy-based efficiency and renewability assessment of biofuel production. Environmental Science and Technology 39(10): 3878-3882.
10 - Lynd, L. R. and M. Q. Wang. (2004). A product-nonspecific framework for evaluating the potential of biomass-based products to displace fossil fuels. Journal of Industrial Ecology 7(3-4): 17-32.
11 - Urbanchuk, J. M. (2009). Contribution of the Ethanol Industry to the Economy of the United States. LECG: Wayne, PA.
12 - RFA. (2011). Biorefinery locations. Renewable Fuels Association: Washington, D.C. Available online: www.ethanolrfa.org.
13 - RFA. (2009a). Growing Innovation. 2009 Ethanol Industry Outlook. Renewable Fuels Association. Washington, D.C. Available at: www.ethanolrfa.org.
14 - RFA. (2009b). Industry resources: co-products. Renewable Fuels Association: Washington, D.C. Available online: www.ethanolrfa.org.
15 - RFA. (2014). Falling walls and rising tides: 2014 annual industry outlook. Renewable Fuels Association: Washington, D.C. Available online: www.ethanolrfa.org.
16 - ERS. (2011). Feed Grains Database: Yearbook Tables. Economic Research Service, U.S. Department of Agriculture: Washington, D.C. Available online: www.ers.usda.gov/data/feedgrains/.
17 - Ingledew, W. M., D. R. Kelsall, G. D. Austin, and C. Kluhspies. (2009). The Alcohol Textbook, 5th Edition. W. M. Ingledew, D. R. Kelsall, G. D. Austin, and C. Kluhspies, ed. Nottingham University Press: Nottingham, UK.
18 - Liu, K. and K. A. Rosentrater. (2011). Distillers Grains: Production, Properties, and Utilization. Boca Raton, FL: CRC Press.
19 - Rosentrater, K. A. (2007). Ethanol processing coproducts – a review of some current constraints and potential directions. International Sugar Journal 109(1307): 1-12.
20 - Rosentrater, K. A. and K. Muthukumarappan. (2006). Corn ethanol coproducts: generation, properties, and future prospects. International Sugar Journal 108(1295): 648-657.
21 - Bhadra, R., K. A. Rosentrater, and K. Muthukumarappan. (2009). Cross-sectional staining and the surface properties of DDGS and their influence on flowability. Cereal Chemistry 86(4): 410-420.
22 - UMN. (2011). The value and use of distillers grains by-products in livestock and poultry feeds. University of Minnesota: Minneapolis, MN. Available online: www.ddgs.umn.edu/.
23 - Staff, C. H. (2005). Question and answer. Biofuels Journal 3(4): 26-27.
24 - Cooper, G. (2006). A brief, encouraging look at ‘theoretical’ distillers grains markets. Distillers Grains Quarterly 1(1): 14-17.
25 - U.S. Grains Council. (2007). An Independent Review of US Grains Council Efforts to Promote DDGS Exports. U.S. Grains Council: Washington, D.C. Available online: www.grains.org/ddgs-information.
26 - FAS. (2009). Foreign Agricultural Service, U. S. Department of Agriculture: Washington, D.C. Available online: www.fas.usda.gov/.
27 - U.S. Grains Council. (2014). Exports of DDGS in 2013 / 2014. Presented at 18th Annual Distillers Grains Symposium, Irving, TX, USA, May 15, 2014.
28 - FAO. (2011). Opportunities and Challenges in Utilizing Co-products of the Biofuel Industry. Rome, Italy: Food and Agriculture Organization of the United Nations.
29 - Hoffman, L. and A. Baker. (2010). Market issues and prospects for U.S. distillers’ grains: supply, use, and price relationships. Report FDS-10k-01. United States Department of Agriculture, Economic Research Service: Washington, D.C. Available online: www.ers.usda.gov.
30 - DTN. (2014). DTN Weekly Distillers Grains Update. Available online: www.dtnprogressivefarmer.com.
31 - Singh, V. and D. B. Johnston. (2009). Fractionation technologies for dry-grind corn processing. Pages 193-207 in: The Alcohol Textbook, 5th Ed. M. W. Ingledew, D. R. Kelsall, G. D. Austin, and C. Kluhspies, ed. Nottingham University Press: Nottingham, UK.
32 - Srinivasan, R., R. A. Moreau, K. D. Rausch, R. L. Belyea, M. D. Tumbleson, and V. Singh. (2005). Separation of fiber from distillers dried grains with solubles (DDGS) using sieving and elutriation. Cereal Chemistry 82: 528-533.